Method for horizontally cutting lattice column in pile of existing station

Abstract

This invention discloses a method for horizontally truncating lattice columns within existing station piles. First, a construction platform is built within the newly constructed foundation pit. The horizontal drilling direction is determined based on the target truncating area of ​​the lattice column. A shape memory alloy drill rod is then driven along the directional casing in the drilling direction, maintaining the austenitic phase throughout the process. When axial deviation is detected, the deviated section of the drill rod is locally cooled and switched to the martensitic phase. The posture is adjusted to correct the deviation. After heating to restore the austenitic phase, drilling continues until the edge of the pile is reached. The drill rod is then extracted to release the core sampling channel. The core sampling drill rod and drill bit are connected to complete the core cutting of the lattice column. After the drilling tool is extracted, grout is injected into the borehole for backfilling. This invention enables precise dynamic correction in situ, improves borehole accuracy and construction efficiency, reduces construction disturbance, and meets the stringent control requirements for construction of operating stations.

Description

Technical Field

[0001] This invention relates to the field of construction technology for underground engineering of urban rail transit, and in particular to a method for horizontally cutting off the internal lattice columns of existing station piles. Background Technology

[0002] With the large-scale development of my country's urban rail transit network, a large number of existing operating stations are entering a period of renovation, expansion, and functional upgrades, making it increasingly common for new foundation pits to be constructed near operating stations. In such projects, the pre-embedded lattice columns in existing stations often conflict with the structure of the new foundation pit, requiring precise cutting of the lattice columns. However, operating stations have extremely stringent control requirements regarding the accuracy of the cutting position and the disturbance of the construction strata. Precise cutting of lattice columns has become a common technical challenge in the field of urban underground engineering.

[0003] For the need to cut off lattice columns in existing railway stations, the horizontal core sampling and cutting process has become the mainstream technical solution in this scenario because it does not require demolition of the existing main structure of the station and has minimal disruption to operations. The core control element of this process is long-distance horizontal directional drilling. Precise axis control during the drilling process is the core prerequisite for ensuring accurate cutting of the lattice columns. The ability to dynamically correct deviations in real time during drilling directly determines the accuracy of the hole formation, the accuracy of the cutting position, and the construction safety, and is the core technical bottleneck of this process.

[0004] Existing horizontal drilling technology has significant shortcomings in its deviation correction techniques. Conventional drill pipes cannot achieve precise dynamic deviation correction in situ during the drilling process. Once an axis deviation occurs, frequent tripping and re-tripping of the drill string to replace specialized deviation correction tools is required. This process is cumbersome, lacks controllability, and easily disturbs the formation around the borehole, causing deformation of existing structures. Some drill strings that can perform deviation correction during drilling lack sufficient accuracy, easily leading to over-correction or under-correction, ultimately resulting in the offset of the lattice column cutoff position, failing to meet the high-precision, low-disturbance control requirements for the construction of operational stations. Summary of the Invention

[0005] In view of the above problems, a method for horizontally truncating the lattice columns within existing station piles is proposed to overcome or at least partially solve the above problems, including:

[0006] A construction platform was built in the new foundation pit, and the horizontal drilling direction was determined according to the target cut-off area of ​​the existing station lattice column. The shape memory alloy drill rod was drilled along the directional casing in the horizontal drilling direction, and the shape memory alloy drill rod maintained the austenitic phase during the drilling process.

[0007] When a deviation in the drilling axis is detected, the shape memory alloy drill rod in the off-center section is locally cooled to switch to the martensitic phase. The drilling posture of the shape memory alloy drill rod is adjusted in the martensitic phase to complete the correction. The shape memory alloy drill rod in the off-center section is heated to restore it to the austenitic phase and drilling continues to the edge of the lattice column pile.

[0008] The shape memory alloy drill rod is pulled out from the directional casing to release the core sampling channel inside the directional casing; the core drill bit is connected to the core sampling drill rod and guided along the core sampling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plate of the lattice column.

[0009] The coring drill bit and coring drill rod are pulled out from the directional casing, and grouting slurry is injected into the hole formed by the directional casing for backfilling grouting.

[0010] Optionally, the horizontal drilling direction is determined based on the target cut-off area of ​​the existing station's lattice columns, including:

[0011] The center coordinates of the top, bottom and cut-off positions of the lattice column are reverse-layouted and verified using a total station. Based on the verified layout results, the horizontal drilling direction perpendicular to the existing station pile axis is determined.

[0012] Adjust the slide elevation angle and horizontal rotation angle of the crawler drilling rig so that the center line of the power head of the crawler drilling rig is on the same horizontal plane as the center point to be cut off of the lattice column. Use steel sections to fix the crawler drilling rig on four sides after adjustment. After verifying that the horizontal drilling direction matches the drilling rig posture correctly, lock the drilling rig.

[0013] Optionally, the shape memory alloy drill pipe is drilled along the directional casing in a horizontal drilling direction, and the shape memory alloy drill pipe maintains the austenitic phase during drilling, including:

[0014] The shape memory alloy drill pipe is inserted into the directional casing to complete coaxial assembly, and the assembled drill bit is locked to the crawler drilling rig's power head. The drill bit is fed at a constant speed along the horizontal drilling direction. During drilling, the temperature of the drill bit body is monitored in real time by the temperature monitoring module built into the shape memory alloy drill pipe to maintain the drill bit temperature in the austenitic phase range and preserve the austenitic phase state of the shape memory alloy drill bit. The directional casing is a seamless metal casing, and the front end of the directional casing is equipped with an alloy cutting tool adapted for drilling soil layers.

[0015] Optionally, when a drilling axis deviation is detected, the shape memory alloy drill pipe in the misaligned section is locally cooled to switch to the martensitic phase. The drilling attitude of the shape memory alloy drill pipe is then adjusted in the martensitic phase to correct the deviation, including:

[0016] During the drilling process, the drilling axis coordinates, drilling torque and feed pressure of the shape memory alloy drill rod are collected in real time through the drilling measurement module. When the deviation value between the drilling axis and the preset horizontal drilling direction exceeds the preset threshold, the drill bit feed is stopped and the drill head is locked.

[0017] The shape memory alloy drill pipe in the off-center section is locally cooled by circumferential spraying with liquid nitrogen. The cooling area is controlled to cover only the off-center section of the axis. The temperature of the drill pipe body is monitored in real time during the cooling process until the shape memory alloy drill pipe in the off-center section is completely switched to the martensitic phase.

[0018] Release the power head lock of the drilling rig, adjust the drilling attitude of the shape memory alloy drill rod through the slide fine adjustment system of the crawler drilling rig, correct the axis deviation, lock the power head of the drilling rig after completing the attitude correction, and check that the drilling axis deviation value has fallen back to within the preset threshold.

[0019] Optionally, the shape memory alloy drill rod in the heated off-center section is restored to the austenitic phase, and drilling continues to the edge of the lattice column pile, including:

[0020] The shape memory alloy drill rod in the off-center section is heated at a constant rate by the electric heating device built into the shape memory alloy drill rod. The temperature of the drill rod body is monitored in real time during the heating process until the shape memory alloy drill rod in the off-center section is completely restored to the austenitic phase.

[0021] After rechecking that the drilling axis is consistent with the horizontal drilling direction, the drilling rig power head is locked and the drill bit is fed at a preset uniform speed. During the drilling process, the drilling depth and the position of the drill bit front end are monitored in real time until the front end of the directional casing reaches the edge of the existing station pile. After verifying that the drilling depth, positioning accuracy and axis deviation meet the design requirements, the drill bit feed is stopped and the drilling rig power head and the position of the directional casing are locked.

[0022] Optionally, the shape memory alloy drill pipe is pulled out from the directional casing to release the core sampling channel inside the directional casing, including:

[0023] Disassemble the connecting joints of the shape memory alloy drill rod section by section in reverse mode; extract the shape memory alloy drill rod completely from the directional sleeve in uniform speed coaxial mode.

[0024] After the drill pipe is completely extracted, an endoscope is used to check the integrity of the inner wall of the directional casing and the stability of the borehole wall. The remaining drill cuttings inside the casing are removed to release a complete and unobstructed core sampling channel inside the directional casing.

[0025] Optionally, after connecting the core drill bit to the core drilling rod, it is guided along the core drilling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plates of the lattice column, including:

[0026] After rigidly connecting the core drill bit and the core drilling rod with threaded coaxial connection, lock it with the power head of the crawler drilling rig; smoothly guide the core drill bit along the core drilling channel until the core drill bit reaches the edge of the lattice column pile body;

[0027] After starting the drilling rig for trial operation and confirming that the drilling tools are operating normally, core cutting operations are carried out on the angle steel and gusset plates of the lattice column. The core cutting bit is a diamond composite core cutting bit, and the cutting teeth of the core cutting bit are arranged in an alternating manner to adapt to concrete breaking and lattice column steel cutting operations.

[0028] Optionally, the shape memory alloy drill rod has a hollow structure. Inside the rod body, there are independent cooling medium channels, heating power supply channels, and temperature monitoring channels. The cooling medium channels are connected to a liquid nitrogen spray device to achieve precise local cooling of the off-center section of the drill rod. The heating power supply channel is electrically connected to an electric heating device built into the rod body to achieve uniform heating of the off-center section of the drill rod. The temperature monitoring channel is signal-connected to a temperature monitoring module built into the rod body to collect the temperature of the drill rod body in real time and achieve closed-loop control of phase changes.

[0029] Optionally, the method also includes: installing automated monitoring sensors on the stress-bearing parts of the existing station floor, track bed and sleepers to monitor the settlement, horizontal displacement and vertical vibration acceleration of the existing station structure in real time.

[0030] Optionally, during the core cutting operation of the angle steel and gusset plates of the lattice column: when drilling into the concrete section of the existing station pile, the power head speed is set to 70 r / min; when the drill bit touches the angle steel and gusset plates of the lattice column, the power head speed is switched to 35 r / min.

[0031] This invention addresses the core shortcomings of existing horizontal drilling techniques, such as cumbersome correction procedures, insufficient accuracy in borehole axis control, and significant construction disturbances. By precisely controlling the dual-phase state of shape memory alloy drill rods, it achieves in-situ dynamic and precise correction during horizontal drilling. The austenitic phase of the drill rod is maintained throughout the drilling process to ensure directional stability. When axis deviation occurs, the phase switching and attitude adjustment of the drill rod can be completed simply by local cooling and heating of the deviated section, eliminating the need for frequent tripping and re-drilling to replace specialized correction tools. This significantly simplifies the correction process and avoids borehole wall and formation disturbances caused by frequent tool disassembly and assembly, effectively improving the accuracy of borehole axis control and ensuring the accuracy of the lattice column cutoff position. Furthermore, the directional casing is simultaneously advanced during drilling to form a stable... With fixed duct support, a complete core sampling channel is directly formed after the shape memory alloy drill rod is extracted, realizing a smooth connection between directional drilling and core cutting processes. Combined with precise positioning of the core cutting operation, the complete severing of the lattice column is achieved. After the core is taken out, backfilling and grouting are carried out through the duct formed by the directional casing, which further ensures the stability of the stratum after the operation. The entire operation does not require demolition of the existing station main structure, which greatly reduces the impact of construction vibration and stratum disturbance on the existing operating station structure. It can fully meet the stringent requirements of operating stations for construction accuracy and deformation control, effectively avoid the adverse effects of construction on the safety of train operation, and improve the construction accuracy, operation efficiency and construction safety of horizontal severing of lattice columns in existing stations. Attached Figure Description

[0032] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the overall layout of the lattice columns within the horizontally truncated existing station piles provided in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the core sampling hole arrangement provided in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the monitoring point layout provided in an embodiment of the present invention;

[0036] Figure 4 This is a flowchart of the severance construction process provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] This invention provides a method for horizontally truncating the internal lattice columns of an existing railway station pile, which may specifically include:

[0039] A construction platform was built in the new foundation pit, and the horizontal drilling direction was determined according to the target cut-off area of ​​the existing station lattice column. The shape memory alloy drill rod was drilled along the directional casing in the horizontal drilling direction, and the shape memory alloy drill rod maintained the austenitic phase during the drilling process.

[0040] When a deviation in the drilling axis is detected, the shape memory alloy drill rod in the off-center section is locally cooled to switch to the martensitic phase. The drilling posture of the shape memory alloy drill rod is adjusted in the martensitic phase to complete the correction. The shape memory alloy drill rod in the off-center section is heated to restore it to the austenitic phase and drilling continues to the edge of the lattice column pile.

[0041] The shape memory alloy drill rod is pulled out from the directional casing to release the core sampling channel inside the directional casing; the core drill bit is connected to the core sampling drill rod and guided along the core sampling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plate of the lattice column.

[0042] The coring drill bit and coring drill rod are pulled out from the directional casing, and grouting slurry is injected into the hole formed by the directional casing for backfilling grouting.

[0043] In the specific implementation, the existing station's as-built data can be obtained first to clarify the layout location of the existing station piles, the cross-sectional dimensions of the existing station's lattice columns, the burial depth parameters, and the three-dimensional coordinate information of the target cut-off area. By combining ground-penetrating radar and borehole detection, the actual spatial coordinates of the existing station's lattice columns and the surrounding environment of the target cut-off area can be verified on-site to confirm that there are no existing underground pipelines, structures, or other obstacles within the horizontal drilling operation path. The complete cross-sectional range of the horizontal cut-off operation can be planned in advance to ensure that the planned cut-off section completely covers the entire cross-section of the existing station's lattice columns, thus completing the pre-confirmation of the cut-off scheme.

[0044] Within the newly constructed foundation pit, the work area corresponding to the existing station lattice column is cleared of loose soil and debris. The original soil in the work area is leveled and compacted. A construction platform is then built in the leveled and compacted work area, with the working surface of the construction platform facing the side of the existing station pile. The elevation of the working surface of the construction platform is consistent with the elevation of the target cut-off area of ​​the existing station lattice column. A total station is used to reverse-lay out the center point of the target cut-off area of ​​the existing station lattice column. Drilling reference points and drilling reference lines are marked on the construction platform, ensuring that the drilling reference lines are perpendicular to the axis of the existing station piles. This determines the horizontal drilling direction. The coordinates of the marked drilling reference points, drilling reference lines, and the target cut-off area of ​​the existing station lattice column are then checked a second time to confirm that the horizontal drilling direction matches the planned cut-off section position correctly.

[0045] Among them, matching the elevation of the working surface of the construction platform with the elevation of the target cut-off area can ensure that the working plane of the subsequent horizontal drilling operation is on the same horizontal plane as the target cut-off section, reducing vertical deviation during the drilling process; the drilling baseline is perpendicular to the axis of the existing station pile, which can ensure that the duct formed by the subsequent drilling completely covers the target cut-off section of the existing station lattice column, providing the foundation for the subsequent complete cut-off of the existing station lattice column.

[0046] The shape memory alloy drill rod is inserted into the internal cavity of the directional casing, completing the coaxial assembly of the shape memory alloy drill rod and the directional casing. A uniform circumferential gap is maintained between the outer wall of the shape memory alloy drill rod and the inner wall of the directional casing. The assembled directional casing and shape memory alloy drill rod are then connected and fixed to the crawler drilling rig's power head. The axis of the crawler drilling rig's power head is adjusted to coincide with the determined horizontal drilling direction. The correspondence between the axis of the drilling rig's power head and the center point of the target cut-off area of ​​the existing station's lattice column is checked again. After confirming that there are no errors, the crawler drilling rig is started, driving the directional casing and shape memory alloy drill rod to advance at a constant speed along the horizontal drilling direction. During the drilling process, the body temperature data of the shape memory alloy drill rod is continuously collected to maintain the body temperature of the shape memory alloy drill rod within the temperature range corresponding to austenite, so that the shape memory alloy drill rod maintains the austenitic phase throughout the drilling process.

[0047] It is understandable that shape memory alloy drill pipes have a stable shape retention capability in the austenitic phase state, which can maintain the preset drilling direction during long-distance horizontal drilling and reduce axial deviation during drilling; the directional casing is fed synchronously with the drill string, which can provide continuous support for the borehole wall formed during drilling, prevent the borehole wall soil from collapsing, and maintain the integrity of the borehole.

[0048] During the drilling process, the drilling axis coordinates of the shape memory alloy drill pipe are collected in real time. The collected drilling axis coordinates are compared with the reference axis corresponding to the horizontal drilling direction. When the comparison result shows that the drilling axis deviates from the reference axis, the drill bit feeding action is stopped.

[0049] While keeping the directional casing in a fixed position, the misaligned section of the shape memory alloy drill rod corresponding to the deviation from the axis is locally cooled. During the cooling process, the body temperature data of the misaligned section of the shape memory alloy drill rod is continuously collected until the misaligned section of the shape memory alloy drill rod completes the transformation from austenite to martensite. While the misaligned section of the shape memory alloy drill rod is in a martensitic state, the drilling attitude of the shape memory alloy drill rod is finely adjusted by the crawler drilling rig power head to correct the deviation of the drilling axis, so that the axis of the shape memory alloy drill rod coincides with the reference axis corresponding to the horizontal drilling direction, thus completing the attitude correction.

[0050] After attitude correction is completed, the shape memory alloy drill rod in the misaligned section is heated, and its body temperature data is continuously collected until the drill rod completes the transformation from martensite to austenite and reverts to the austenite phase. The crawler drilling rig is then started, and the drill bit is fed at a constant speed along the horizontal drilling direction. During drilling, the coordinates of the drilling axis are checked in stages until the front end of the directional casing reaches the edge of the existing station pile where the existing station lattice column is located. At this point, the drill bit feeding is stopped, and the actual position of the front end of the directional casing is checked against the coordinates of the target cut-off area to confirm that the drill bit's arrival position matches the planned cut-off section position correctly.

[0051] Shape memory alloy drill pipes have good plastic deformation capabilities in the martensitic phase state, and can adjust their shape under the action of external force to adjust the drilling posture. After the correction is completed, the shape memory alloy drill pipes return to the austenitic phase, which can stably maintain the axial shape after correction, avoid the axial deviation from occurring again during drilling, and ensure the directional accuracy of subsequent drilling operations.

[0052] After stopping the drill string feed, keep the directional casing in a fixed position. Disconnect the shape memory alloy drill rod from the crawler drilling rig's power head. Extract the shape memory alloy drill rod completely from the internal cavity of the directional casing at a uniform speed and coaxially. During extraction, avoid the shape memory alloy drill rod hitting the inner wall of the directional casing. After the shape memory alloy drill rod is completely extracted, the internal cavity of the directional casing forms a complete and unobstructed core sampling channel. Verify the unobstructedness and axial direction of the core sampling channel. After confirming that the channel axis is consistent with the horizontal drilling direction, rigidly connect the core sampling drill bit and the core sampling drill rod coaxially. As a whole, connect the core sampling drill rod and the core sampling drill bit. Connect and fix the crawler drilling rig to the power head, start the crawler drilling rig, and smoothly guide the core drill bit and core drilling rod along the core operation channel inside the directional casing in a low-speed rotation manner until the front end of the core drill bit reaches the edge of the existing station pile where the existing station lattice column is located. Check again that the working path of the core drill bit matches the pre-planned cut-off section range. After confirming that the core operation can completely cover the angle steel and gusset plate of the existing station lattice column, drive the crawler drilling rig to rotate and feed the core drill bit to cut the angle steel and gusset plate of the existing station lattice column inside the existing station pile until the full cross-section cutting of the existing station lattice column in the target cut-off area is completed.

[0053] The core sampling channel is formed by a fixed directional casing, which ensures that the guide path of the core sampling drill rod and core sampling drill bit is consistent with the preset horizontal drilling direction, avoids path deviation during core cutting, and ensures the accuracy of the cut-off position of the existing station lattice column.

[0054] After completing the core cutting operation of the existing station lattice column, stop the operation of the crawler drilling rig, disconnect the core drilling rod from the crawler drilling rig power head, and completely extract the core drilling rod and core drill bit from the internal cavity of the directional casing by rotating at a constant speed. During the extraction process, clean the cutting residue attached to the surface of the core drilling rod and core drill bit. After the core drilling rod and core drill bit are completely extracted, clean the cutting residue inside the borehole.

[0055] After confirming that there are no residual debris inside the duct, insert the grouting pipe into the bottom of the duct formed by the directional sleeve, and inject grout into the duct through the grouting pipe. During the grouting process, slowly pull out the grouting pipe at a uniform speed to allow the grout to completely fill the internal space of the duct, thus completing the backfill grouting. After the grouting is completed, seal the opening of the duct.

[0056] Grouting backfilling based on the duct formed by the directional casing can ensure that the filling range of the grouting slurry is completely matched with the duct formed by drilling, realize the equal replacement of the soil in the duct, improve the stability of the formation after the operation is completed, and reduce the possibility of formation settlement and deformation.

[0057] In one or more embodiments of the present invention, determining the horizontal drilling direction based on the target cut-off area of ​​the existing station lattice column includes:

[0058] The center coordinates of the top, bottom and cut-off positions of the lattice column are reverse-layouted and verified using a total station. Based on the verified layout results, the horizontal drilling direction perpendicular to the existing station pile axis is determined.

[0059] Adjust the slide elevation angle and horizontal rotation angle of the crawler drilling rig so that the center line of the power head of the crawler drilling rig is on the same horizontal plane as the center point to be cut off of the lattice column. Use steel sections to fix the crawler drilling rig on four sides after adjustment. After verifying that the horizontal drilling direction matches the drilling rig posture correctly, lock the drilling rig.

[0060] In practical applications, after the total station is set up, a double backsight point orientation verification method can be adopted. Two permanent control points that are visible to the work area and whose coordinates have been verified by a third party are selected as backsight points. Only after the coordinate deviation obtained from the two orientations is not greater than the allowable range of the specification can the layout work be started.

[0061] During the layout process, the four exposed angle steel corners of the existing station lattice column were used as reference positioning points. The three-dimensional coordinates of each angle steel corner were collected, and the center coordinates of the lattice column section were obtained through geometric calculation fitting, replacing the single center point acquisition method and reducing the measurement error caused by the irregularity of the lattice column section. Combined with the actual axis data of the existing station piles obtained by on-site drilling, the pile axis marked on the as-built drawings was corrected. The vertical horizontal drilling direction was calculated based on the corrected actual pile axis. The cross reference line of the horizontal drilling direction was marked on the hardened surface of the construction platform by grooving. At the same time, fixed check piles were set at both ends of the reference line for dynamic direction verification during the operation.

[0062] Before the drilling rig is positioned, anti-slip steel plates can be laid at the track parking location. The steel plates are fixed to the hardened surface of the work platform with expansion bolts to prevent the tracks from slipping and shifting during operation. After the drilling rig is positioned, the horizontality of the drilling rig body is pre-adjusted using a two-way level. The horizontal deviation of the body in both longitudinal and transverse directions is controlled within the allowable range of the specifications before adjusting the slide parameters. The slide adjustment adopts a method of coarse adjustment followed by fine adjustment. First, the horizontal rotation angle and elevation angle are coarsely adjusted using the slide cylinder to make the center line of the power head initially coincide with the baseline. Then, the precision is calibrated using the slide fine adjustment screw. During the calibration process, a laser line projector and a total station are used for double verification to ensure that the elevation deviation and plane deviation between the center line of the power head and the center point to be cut off of the lattice column meet the preset requirements.

[0063] When fixing the four-sided limit, steel plates can be pre-embedded on the construction platform at the positions corresponding to the four directions of the drilling rig body. One end of the steel section is fully welded to the pre-embedded steel plate, and the other end is fitted to the drilling rig body and then steel wedges are driven in to wedge tightly, eliminating the gap between the steel section and the body and preventing the body from shaking during operation. After the limit is fixed, first lock the horizontal rotation angle and elevation angle adjustment mechanism of the slide, and then lock the drilling rig travel braking mechanism. After locking, the matching of the center line of the power head and the horizontal drilling direction is finally checked again. Only after confirming that there are no errors can subsequent drilling operations be carried out.

[0064] In one or more embodiments of the present invention, a shape memory alloy drill rod is drilled along a directional casing in a horizontal drilling direction, wherein the shape memory alloy drill rod maintains an austenitic phase during drilling, including:

[0065] The shape memory alloy drill pipe is inserted into the directional casing to complete coaxial assembly, and the assembled drill bit is locked to the crawler drilling rig's power head. The drill bit is fed at a constant speed along the horizontal drilling direction. During drilling, the temperature of the drill bit body is monitored in real time by the temperature monitoring module built into the shape memory alloy drill pipe to maintain the drill bit temperature in the austenitic phase range and preserve the austenitic phase state of the shape memory alloy drill bit. The directional casing is a seamless metal casing, and the front end of the directional casing is equipped with an alloy cutting tool adapted for drilling soil layers.

[0066] In practical applications, before assembly, the outer wall of the shape memory alloy drill rod and the inner wall of the directional casing should be cleaned to remove oil, rust, and debris. The roundness of the outer wall of the drill rod and the inner wall of the casing should be checked one by one, and any components with deformation defects should be discarded. The directional casing is placed horizontally on an assembly support arranged at equal intervals along the axis to prevent the casing from bending vertically due to its own weight. Then, the shape memory alloy drill rod is smoothly and coaxially inserted into the directional casing from the tail end. During the insertion process, the circumferential gap between the outer wall of the drill rod and the inner wall of the casing can be measured with a feeler gauge after each section of drill rod is pushed in to ensure that the circumferential gap is uniform throughout the entire section and that the gap deviation is controlled within the preset range. After insertion, coaxial limiting guide sleeves are fitted at both ends of the drill rod and the casing to restrict the radial movement of the drill rod in the casing, thus completing the coaxial assembly.

[0067] Before connecting the drill bit to the crawler drilling rig's power head, clean the connecting threads of the power head's output end and the drill rod's tail end, apply thread protective grease, and complete the connection using a rigid threaded connection method. After connection, use a torque wrench to tighten the connecting fasteners diagonally in stages according to the preset torque value. After tightening, install anti-loosening and anti-reverse parts at the joint, start the power head for a low-speed no-load test run, check the coaxiality of the connection between the drill bit and the power head, and after confirming that there is no radial runout and no loose connection, complete the locking of the drill bit and the power head.

[0068] After the drill string is locked, a trial drilling operation is carried out. The feed rate and rotation speed are set lower than the normal operating values. After drilling a preset short distance, the operation is paused to check the alignment of the drill string's drilling axis with the horizontal drilling direction. After confirming that there is no axis deviation, a constant feed rate and rotation speed are set, and continuous uniform feed operation is carried out along the horizontal drilling direction. During the feed process, the feed pressure and rotation torque data of the drill string are collected in real time. When the parameters fluctuate abnormally, the feed rate is finely adjusted to maintain parameter stability and avoid axis deviation caused by sudden changes in feed rate. At the same time, after drilling a preset fixed depth, the feed is paused and the drill string's drilling axis is checked. After confirming that the direction is correct, the operation continues.

[0069] Before starting the drilling operation, the multiple temperature monitoring modules built into the shape memory alloy drill pipe and arranged at equal intervals along the axial direction can be calibrated by powering on to confirm that the acquisition frequency and acquisition accuracy of the modules meet the preset requirements.

[0070] During drilling, the temperature monitoring module can transmit the body temperature data of each section of the drill rod to the construction control terminal at a fixed frequency in real time. The construction control terminal has a pre-stored austenitic phase transformation temperature range corresponding to the shape memory alloy drill rod. When the temperature of a certain section of the drill rod is detected to be close to the lower limit of the austenitic phase range, the auxiliary heat preservation device built into the drill rod is activated to maintain the temperature of the drill rod. When the temperature of the drill rod is detected to be higher than the upper limit of the austenitic phase range, the air-cooling heat dissipation structure built into the drill rod is activated to reduce the body temperature of the drill rod, ensuring that the body temperature of the entire section of the drill rod is stable within the austenitic phase range throughout the drilling process, and continuously maintaining the austenitic phase state of the shape memory alloy drill rod.

[0071] Directional casing can be made of seamless metal casing with uniform wall thickness. Each casing section has matching trapezoidal threaded connectors at both ends. After adjacent casings are joined, sealing tape is wrapped around the joints to prevent soil or mud from entering the casing during drilling. The alloy cutting tool at the front end of the directional casing uses multiple sets of cutting teeth evenly and alternately arranged along the circumference of the casing front end. The cutting edge angle of the cutting teeth is adapted to the soil properties of the working area. The outer diameter of the cutting tool is consistent with the outer diameter of the casing. A limiting step matching the inner wall of the casing is set at the rear end of the cutting tool to ensure coaxial connection between the cutting tool and the casing. During drilling, it rotates synchronously with the casing to feed, completing soil cutting and borehole formation.

[0072] In one or more embodiments of the present invention, when a drilling axis deviation is detected, the shape memory alloy drill pipe in the deviated section is locally cooled to switch to the martensitic phase, and the drilling posture of the shape memory alloy drill pipe is adjusted in the martensitic phase to complete the deviation correction, including:

[0073] During the drilling process, the drilling axis coordinates, drilling torque and feed pressure of the shape memory alloy drill rod are collected in real time through the drilling measurement module. When the deviation value between the drilling axis and the preset horizontal drilling direction exceeds the preset threshold, the drill bit feed is stopped and the drill head is locked.

[0074] The shape memory alloy drill pipe in the off-center section is locally cooled by circumferential spraying with liquid nitrogen. The cooling area is controlled to cover only the off-center section of the axis. The temperature of the drill pipe body is monitored in real time during the cooling process until the shape memory alloy drill pipe in the off-center section is completely switched to the martensitic phase.

[0075] Release the power head lock of the drilling rig, adjust the drilling attitude of the shape memory alloy drill rod through the slide fine adjustment system of the crawler drilling rig, correct the axis deviation, lock the power head of the drilling rig after completing the attitude correction, and check that the drilling axis deviation value has fallen back to within the preset threshold.

[0076] Specifically, multiple sets of measurement-while-drilling (MWD) units are arranged at equal intervals along the axial direction of the shape memory alloy drill pipe. Each set of units integrates coordinate acquisition, torque acquisition, and feed pressure acquisition functions. During drilling, all MWD units synchronously transmit the acquired data to the construction control terminal at a fixed frequency. The construction control terminal fits and compares the real-time acquired full-section drilling axis coordinates with the preset horizontal drilling direction reference axis, calculates the axis deviation values ​​in the planar and vertical directions, and combines the fluctuation data of drilling torque and feed pressure to generate a drilling axis deviation curve, accurately locating the starting depth, ending depth, and maximum deviation position of the axis deviation segment.

[0077] When the axis deviation value in any direction exceeds the preset threshold, the feed action of the drill bit is stopped first to maintain the static state of the drill bit. Then, the rotation mechanism and feed mechanism of the crawler drill head are locked in sequence. At the same time, the position of the directional casing is locked by the orifice clamping device to prevent the directional casing from axial displacement or radial deflection, so as to provide a stable borehole reference for subsequent correction operations.

[0078] Based on the depth range of the offset section obtained from the positioning, the segmented cooling medium channels built into the shape memory alloy drill pipe are matched. The circumferential spray control valve of the corresponding channel of the offset section is opened, while the control valves of the other non-offset section channels are closed. At the same time, a heat-insulating sleeve is installed on the outer wall of the drill pipe in the non-offset section to block the transfer of cold energy to the non-offset section. Liquid nitrogen is delivered to the cooling medium channel corresponding to the offset section in a preset low-pressure uniform speed mode, and liquid nitrogen is uniformly sprayed onto the drill pipe body through the circumferential spray holes on the outer wall of the offset section of the drill pipe to implement local cooling.

[0079] During the cooling process, temperature monitoring points are set up at equal intervals along the circumference and axial direction within the offset section to collect real-time temperature data of the entire cross-section of the drill pipe body. Once the temperature of all monitoring points has stably dropped below the martensitic phase transformation temperature range, the cooling state is maintained for a preset duration to confirm that the shape memory alloy drill pipe in the offset section has completely completed the transformation from austenitic phase to martensitic phase. Then, the liquid nitrogen delivery valve is closed, and the spraying operation is stopped.

[0080] After confirming the phase transition, first release the locking state of the power head rotation mechanism and the feed mechanism of the crawler drilling rig, and keep the connection between the power head and the shape memory alloy drill rod locked. Then, start the slide fine-tuning system of the crawler drilling rig and adjust the drilling attitude of the drill rod in a step-by-step manner. The change in the horizontal rotation angle and elevation angle of a single adjustment shall not exceed the preset value. After each attitude adjustment, the drilling axis coordinates are collected in real time by the drilling measurement unit to check the correction of the axis deviation and avoid overcorrection.

[0081] When the verification results show that the drilling axis coincides with the preset horizontal drilling direction reference axis and the axis deviation value falls back to within the preset threshold, the attitude adjustment is stopped, and the slewing mechanism and feed mechanism of the crawler drilling rig power head are locked again in sequence. The drilling axis coordinates, drilling torque and feed pressure data of the entire drill pipe are collected by the drilling measurement unit to complete the full parameter verification and confirm that the correction effect meets the preset requirements.

[0082] In one or more embodiments of the present invention, the heated offset section of the shape memory alloy drill rod is restored to the austenitic phase, and drilling continues to the edge of the lattice column pile body, including:

[0083] The shape memory alloy drill rod in the off-center section is heated at a constant rate by the electric heating device built into the shape memory alloy drill rod. The temperature of the drill rod body is monitored in real time during the heating process until the shape memory alloy drill rod in the off-center section is completely restored to the austenitic phase.

[0084] After rechecking that the drilling axis is consistent with the horizontal drilling direction, the drilling rig power head is locked and the drill bit is fed at a preset uniform speed. During the drilling process, the drilling depth and the position of the drill bit front end are monitored in real time until the front end of the directional casing reaches the edge of the existing station pile. After verifying that the drilling depth, positioning accuracy and axis deviation meet the design requirements, the drill bit feed is stopped and the drilling rig power head and the position of the directional casing are locked.

[0085] In practical applications, before heating operations, the thermal insulation sleeve on the outer wall of the off-center section of the drill rod can be removed first. The electric heating device built into the shape memory alloy drill rod and arranged in sections along the axial direction can be checked for continuity. It is confirmed that the insulation performance of the power supply circuit of the heating unit corresponding to the off-center section meets the standard, and the heating unit of the non-off-center section is in a power-off isolation state to prevent heat from spreading to the non-off-center section.

[0086] A staged uniform heating program is set. First, the temperature of the drill pipe body in the off-center section is uniformly raised to the starting temperature of the transformation from martensite to austenite at a preset constant heating rate. The temperature is then held for a preset duration to ensure that the temperature of the drill pipe body in the off-center section is evenly distributed. Then, the temperature is raised uniformly at the same constant heating rate until the temperature of the drill pipe body enters the preset austenite phase stable range.

[0087] During the heating process, temperature monitoring points are arranged at equal intervals along the circumference and axial direction within the offset section to collect the body temperature data of the entire cross section of the drill pipe in real time at a fixed frequency. When the temperature of all monitoring points is stable within the austenitic phase range, the temperature is continuously maintained for a preset time to confirm that the shape memory alloy drill pipe in the offset section has completely completed the transformation from martensite phase to austenite phase and that the phase state is uniform throughout the section. Then, the electric heating device is turned off, and the built-in heat preservation module of the drill pipe is activated to maintain the temperature stability of the drill pipe.

[0088] After the phase recovery confirmation is completed, the three-dimensional coordinates of the drilling axis of the entire drill pipe are collected through the built-in measurement-while-drilling module of the shape memory alloy drill pipe. The collected axis of the entire section is fitted and compared with the preset horizontal drilling direction reference axis. At the same time, the axis of the exposed section of the drill pipe is checked a second time through the laser line projector fixed on the construction platform. The drilling axis is double-confirmed to be completely consistent with the horizontal drilling direction, with no residual deviation.

[0089] After verification, the locking status of the crawler drilling rig's power head is released sequentially, first releasing the feed mechanism lock, then the slewing mechanism lock, ensuring the connection between the power head and the shape memory alloy drill rod remains secure. A trial feed operation is then conducted at a preset uniform speed lower than the normal operating speed. After drilling a preset short distance, the operation is paused. Once the drilling axis is verified to be free of deviation, continuous feeding is then conducted at the preset uniform speed for normal operation. During feeding, the slewing torque and feed pressure data are monitored in real time. If abnormal fluctuations occur in the parameters, the feed speed is fine-tuned to maintain parameter stability and prevent further deviation of the drilling axis.

[0090] During continuous feeding operations, the displacement sensor built into the crawler drilling rig's power head collects the feed footage of the drill bit in real time and calculates the drilling depth simultaneously. After each preset fixed feed, feeding is paused to verify the drilling depth and the three-dimensional coordinates of the drill bit's front end. These coordinates are then compared with the design coordinates of the edge of the existing station pile body, which have been pre-detected and determined. At the same time, the change in the drill bit's rotation torque is monitored in real time. The relative position between the drill bit's front end and the edge of the existing station pile body is double-confirmed using the three parameters: drilling depth, front end coordinates, and rotation torque.

[0091] When the front end of the directional casing reaches the edge of the existing station pile, the drilling tool feed is stopped. The cumulative drilling depth, the positioning accuracy of the front end of the drilling tool, and the deviation of the entire drilling axis from the horizontal drilling direction are comprehensively checked. After confirming that all parameters meet the design requirements, the rotation mechanism and feed mechanism of the crawler drilling rig power head are locked in sequence. The directional casing is axially and radially limited and locked by the orifice clamping device. At the same time, auxiliary limiting components are installed between the exposed section of the directional casing and the hardened structure of the construction platform to prevent displacement of the directional casing and provide a stable borehole reference for subsequent operations.

[0092] In one or more embodiments of the present invention, the shape memory alloy drill pipe is extracted from the directional casing to release the core sampling channel inside the directional casing, including:

[0093] Disassemble the connecting joints of the shape memory alloy drill rod section by section in reverse mode; extract the shape memory alloy drill rod completely from the directional sleeve in uniform speed coaxial mode.

[0094] After the drill pipe is completely extracted, an endoscope is used to check the integrity of the inner wall of the directional casing and the stability of the borehole wall. The remaining drill cuttings inside the casing are removed to release a complete and unobstructed core sampling channel inside the directional casing.

[0095] Specifically, before disassembly, the directional casing can be locked axially and radially using a borehole clamping device to keep it in a fixed position and prevent it from shifting during disassembly. At the same time, disconnect the crawler drill head from the tail end of the shape memory alloy drill rod, clean the debris and oil from the joint of the exposed section of the drill rod, and install a liftable coaxial support bracket below the exposed section of the drill rod. The support height of the bracket should be consistent with the center elevation of the directional casing to provide coaxial support for the disassembly and extraction of the drill rod and prevent the drill rod from bending vertically due to its own weight.

[0096] Using the low-speed reverse mode of the drill rig's power head, the connecting joints of the shape memory alloy drill rods are disassembled section by section. The reverse rotation speed is controlled within a preset low speed range, and the reverse torque is matched with the design disassembly torque of the drill rod joint to avoid excessive torque damaging the joint threads. After disassembling each section of the drill rod joint, the section is first smoothly pulled out along the coaxial direction, impurities are cleaned from the joint threads, and protective grease is applied. Then, it is placed on a special storage bracket. The remaining drill rods left in the casing are then coaxially supported and adjusted to ensure that the axis of the remaining drill rods always coincides with the axis of the directional casing. The above operation is repeated until all drill rod joints are disassembled.

[0097] After all joints are disassembled, a coaxial traction guide is installed at the tail end of the drill rod. The outer diameter of the traction guide is matched with the inner diameter of the directional casing to limit the radial movement of the drill rod during extraction. A uniform speed traction device is used in conjunction with the drilling rig's auxiliary feed mechanism to completely extract the shape memory alloy drill rod from the directional casing along the coaxial direction at a preset constant speed. During the extraction process, the drill rod is continuously supported by a liftable coaxial support bracket. The coaxiality of the drill rod is checked every preset length extracted to control the radial sway of the drill rod within a preset range, preventing the outer wall of the drill rod from hitting the inner wall of the directional casing, preventing scratches and deformation of the inner wall of the casing, and avoiding disturbance of the borehole soil.

[0098] After the drill pipe is completely withdrawn, the industrial endoscope is inserted into the casing along the axial direction of the directional casing and moved along the entire length of the casing at a preset uniform speed. The surface condition of the inner wall of the casing is recorded throughout the process, with a focus on checking for damage such as dents, scratches, and deformation on the inner wall of the casing. At the same time, the condition of the soil in the borehole is photographed through the endoscope to check for conditions such as soil collapse and rockfall that may affect the stability of the borehole wall, thus forming a complete inspection record.

[0099] After inspection, a slag-removing piston adapted to the inner diameter of the casing is used in conjunction with low-pressure compressed air to reciprocate and purge the entire casing section to remove residual drill cuttings, soil debris, and other impurities. After purging, the cleanliness of the casing is checked again using an endoscope. At the same time, a standard gauge is used to check the diameter of the casing section to confirm that there is no blockage or deformation inside the casing, forming a complete and unobstructed channel for core sampling. After the inspection is completed, a temporary sealing cap is installed at the casing orifice to prevent external debris from entering the casing.

[0100] In one or more embodiments of the present invention, after connecting the core drill bit to the core drilling rod, it is guided along the core drilling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plates of the lattice column, including:

[0101] After rigidly connecting the core drill bit and the core drilling rod with threaded coaxial connection, lock it with the power head of the crawler drilling rig; smoothly guide the core drill bit along the core drilling channel until the core drill bit reaches the edge of the lattice column pile body;

[0102] After starting the drilling rig for trial operation and confirming that the drilling tools are operating normally, core cutting operations are carried out on the angle steel and gusset plates of the lattice column. The core cutting bit is a diamond composite core cutting bit, and the cutting teeth of the core cutting bit are arranged in an alternating manner to adapt to concrete breaking and lattice column steel cutting operations.

[0103] Specifically, before coring, the internal threads of the coring drill bit and the external threads at both ends of the coring drill rod should be cleaned to remove burrs, oil, and metal filings from the thread surfaces. Appropriate thread lubricating grease should be applied to the thread meshing surfaces. The coring drill bit and the coring drill rod should be placed on a coaxial mounting bracket, and the central axes of the two should be completely aligned to complete the thread connection. A torque wrench should be used to tighten the connection joint in stages at a constant speed with a preset torque. After tightening, an anti-loosening and anti-reverse device should be installed at the joint. A dial indicator should be used to check the radial runout after the coring drill bit and the coring drill rod are connected, and the radial runout should be controlled within a preset range to confirm that the coaxiality of the two meets the requirements.

[0104] Connect the end of the core drilling rod to the power head of the crawler drilling rig, clean the connecting threads at the output end of the power head and apply lubricating grease, and complete the connection and locking with the same preset torque. Start the power head to perform a jog test to confirm that the connection between the drill bit and the power head is not loose and there is no abnormal radial runout.

[0105] After completing the connection and locking of the drill string, remove the temporary sealing cap from the orifice of the directional casing, clean the debris at the orifice, and install a liftable coaxial support bracket below the exposed section of the core drilling rod. Adjust the support height of the bracket to be consistent with the center elevation of the directional casing to provide full coaxial support for the drill string introduction. Start the crawler drilling rig and drive the drill string to rotate at a preset low speed. At the same time, guide the core drill bit smoothly along the core drilling channel inside the directional casing at a preset constant speed. During the introduction process, pause the feed action after advancing a preset fixed length to check the depth and coaxiality of the drill string. Control the radial wobble of the drill string within the preset range to avoid the core drill bit hitting the inner wall of the directional casing and to prevent damage to the inner wall of the casing and the cutting teeth of the drill bit.

[0106] During the import process, the rotational torque and feed pressure of the crawler drilling rig are monitored in real time, and the drilling depth is calculated synchronously and compared with the pre-calibrated design depth of the existing station pile edge. When the rotational torque shows a stable change and the drilling depth reaches the design value, the feeding action is paused, the three-dimensional coordinates of the drill bit front end are checked, and it is confirmed that the cutting end face of the core drill bit has reached the edge of the existing station pile where the lattice column is located.

[0107] After confirming that the core drill bit is in place, start the crawler drilling rig to conduct a staged test run. First, perform a no-load rotation test run at the preset first speed for a preset duration to check the rotational stability of the drill bit, the operating status of the crawler drilling rig's power head, and the tightness of each connection joint. After confirming that there are no abnormal noises, leaks, or loose connections in the drill bit, increase the speed to the preset second speed for a second no-load test run for the same preset duration. Once the operating status of the drill bit is verified to be normal, the test run process is completed.

[0108] After the trial run is successful, the feed mechanism of the crawler drilling rig is started, and the core drill bit is rotated and fed at a preset constant feed speed to carry out core cutting operations on the lattice column angle steel and gusset plate in the existing station pile. During the operation, the changes in rotation torque and feed pressure are monitored in real time. At the same time, the concrete debris and steel chips generated by cutting are continuously discharged from the hole through circulating flushing fluid to avoid the accumulation of chips on the cutting end face and affect the continuity of cutting operations.

[0109] The core drill bit uses a diamond composite core drill bit. Multiple sets of cutting teeth are evenly distributed circumferentially at the front end of the steel matrix of the drill bit. These cutting teeth can be arranged in a staggered pattern, with adjacent cutting teeth staggered in both the circumferential and axial directions. Half of the cutting teeth use coarse-grained diamond composites suitable for concrete crushing, while the remaining half use fine-grained diamond composites suitable for steel cutting. These two types of cutting teeth are alternately and staggered along the circumference of the drill bit matrix. All cutting teeth have a consistent exit height, and the spacing between adjacent cutting teeth forms a continuous spiral chip removal groove. The lead of the chip removal groove is adapted to the rotational speed of the cutting operation, allowing for smooth removal of various types of chips generated during cutting. The staggered arrangement of the cutting teeth creates a continuous, blind-zone-free cutting section during rotational cutting, enabling efficient crushing of pile concrete and smooth cutting of lattice column angle steel and gusset plates, reducing the probability of tooth breakage and drill jamming during the cutting process.

[0110] In one or more embodiments of the present invention, the shape memory alloy drill rod has a hollow structure. The drill rod body contains independent cooling medium channels, heating power supply channels, and temperature monitoring channels. The cooling medium channels are connected to a liquid nitrogen spray device to achieve precise local cooling of the off-center section of the drill rod. The heating power supply channel is electrically connected to an electric heating device built into the rod body to achieve uniform heating of the off-center section of the drill rod. The temperature monitoring channel is signal-connected to a temperature monitoring module built into the rod body to collect the temperature of the drill rod body in real time, achieving closed-loop control of phase changes.

[0111] Specifically, the shape memory alloy drill rod can adopt a single-section splicing structure. The rod body of each section is integrally hot-extruded from a nickel-titanium shape memory alloy material that matches the phase transition temperature. The rod body has a hollow structure with a central cavity as the basic through cavity. Along the circumference of the central cavity, three independent and non-connected axial channels are integrally formed inside the wall thickness of the rod body. These are a cooling medium channel, a heating power supply channel, and a temperature monitoring channel. The three channels are evenly spaced along the circumference of the rod body, and the channels are completely isolated by the alloy material of the rod body, with no connecting gaps, to avoid mutual interference between the media and cables in different channels.

[0112] Both ends of a single drill pipe section can be machined with matching male and female threaded connectors. At the connector, corresponding to the three channels, there are mating interfaces with seals. After adjacent drill pipe sections are spliced ​​and locked, the mating interfaces of the corresponding channels are completely aligned and fitted. The high and low temperature resistant seals in the connectors achieve independent sealing at the channel mating points, ensuring that the three channels of the entire drill pipe section are completely independent, without cross-contamination or leakage after splicing.

[0113] The cooling medium channel can be a circular sealed cavity. The inner wall of the cooling medium channel of a single drill rod is treated with low-temperature corrosion resistance. Independent electromagnetic control valves are arranged at equal intervals along the axial direction in the channel. Each section of the drill rod is equipped with an independent control valve, which can control the opening and closing of a single section of the channel. The outer wall of the rod body is equipped with multiple circumferential spray holes evenly arranged along the circumference corresponding to the position of the cooling medium channel. The inner end of the spray hole is connected to the cooling medium channel, and the outer end is connected to the outer wall of the rod body. Each spray hole is equipped with a one-way valve, which only allows the cooling medium to flow out from the inside of the channel to the outer wall of the rod body in one direction.

[0114] After the drill pipe is assembled, the end of the cooling medium channel is connected to the liquid nitrogen spraying device via a low-temperature resistant high-pressure hose. The liquid nitrogen spraying device can open the electromagnetic control valve of the drill pipe segment corresponding to the offset segment according to the location of the offset segment, and deliver liquid nitrogen into the corresponding channel. The circumferential spray holes of the segment achieve localized and precise cooling of the offset section of the drill pipe. The channel control valve of the non-offset segment remains closed, and there is no liquid nitrogen output to prevent the cold energy from spreading to non-target areas.

[0115] The heating power supply channel is a sealed cavity with an insulating protective layer on the inner wall. Multiple sets of high-temperature resistant insulated power supply cables are installed inside the channel. The cables are laid along the entire axial direction of the channel. When adjacent single drill rod sections are spliced, the power supply cables in the corresponding channels are connected through waterproof insulated plug joints at the channel joints to ensure the continuity and insulation of the entire power supply line.

[0116] The wall thickness of the rod corresponds to the position of each drill rod section, and each section is equipped with an independent electric heating device. The electric heating device adopts a sheet-like resistance heating structure that fits into the inner wall of the rod. Each group of electric heating devices is independently electrically connected to the power supply cable of the corresponding section in the heating power supply channel, and the start-up, shutdown and heating power of the electric heating device of a single drill rod section can be controlled individually.

[0117] After the drill pipe is assembled, the end of the power supply cable in the heating power supply channel is electrically connected to the temperature control power supply system of the construction control terminal. Depending on the location of the deviation section, power is supplied only to the electric heating device of the drill pipe segment corresponding to the deviation section, so as to achieve uniform heating of the drill pipe in the deviation section at a preset heating rate. The electric heating device of the non-deviation section is kept off to avoid heat transfer to non-target areas.

[0118] The temperature monitoring channel can be a sealed cavity with an electromagnetic shielding layer on the inner wall. Multiple sets of shielded temperature signal cables run through the channel, extending along its entire axial length. When adjacent drill pipe sections are joined, the signal cables within the corresponding channels are connected via shielded connectors at the channel joints, ensuring stable signal transmission throughout the entire section and preventing electromagnetic interference during drilling. Along the drill pipe's axial direction, multiple temperature monitoring modules are evenly spaced within each drill pipe section. These modules utilize patch-type temperature sensors, and each module is independently connected to the corresponding segment of the signal cable within the temperature monitoring channel, enabling real-time acquisition of temperature data from the drill pipe body at the corresponding location.

[0119] After the drill pipe is assembled, the end of the signal cable in the temperature monitoring channel is connected to the temperature control system of the construction management terminal. This allows for real-time transmission of body temperature data from each monitoring point along the entire drill pipe section. Based on the real-time temperature data, the construction management terminal controls the control valve of the cooling medium channel and the power output of the heating power supply channel, adjusting cooling and heating parameters in real time to ensure that the drill pipe body temperature remains stable within the temperature range corresponding to the target phase state, thus achieving closed-loop control of drill pipe phase state changes.

[0120] In one or more embodiments of the present invention, the method further includes: deploying automated monitoring sensors on the stress-bearing parts of the existing station floor, track bed and sleepers to monitor the settlement, horizontal displacement and vertical vibration acceleration of the existing station structure in real time.

[0121] Specifically, before the operation, the structural as-built drawings and operation and maintenance data of the existing station can be obtained to clarify the structural form, stress system, reinforcement layout location and existing deformation monitoring benchmark location of the existing station floor, track bed and sleepers. Combined with the working surface location of the horizontal cut-off operation and the preset construction impact range, the monitoring area is divided and the monitoring points are planned within the monitoring area.

[0122] Monitoring points can be prioritized for placement at stress-sensitive areas of existing station structures. Specifically, for the existing station floor slab, monitoring points should be placed around the bases of structural columns near the work surface, at the mid-span of the longitudinal and transverse load-bearing beams of the floor slab, and at the internal corners where the floor slab connects to the side walls. For the track bed, monitoring points should be placed at both ends of the track bed slab below the sleeper support platform, on both sides of the track bed expansion joints, and at the edge where the track bed slab connects to the floor slab. For the sleepers, monitoring points should be placed at both ends of the support platform corresponding to the rail fixing, and at the stress-bearing joint between the sleeper and the track bed slab. Simultaneously, at least three benchmark control points should be placed in the stable structural areas of the existing station outside the work influence zone. These benchmark control points should have no visual obstruction between them and all monitoring points, providing a stable reference for the monitoring operation.

[0123] According to the type of monitoring parameters, adaptive automatic monitoring sensors are arranged correspondingly. Specifically, hydrostatic level sensors are adopted for settlement monitoring, automatic monitoring prisms matched with total stations are adopted for horizontal displacement monitoring, and piezoelectric vibration acceleration sensors are adopted for vertical vibration acceleration monitoring.

[0124] Before arranging all sensors, the structural surface at the arrangement points shall be cleaned first to remove floating dust, oil stains and impurities on the surface, so as to ensure that the arrangement surface is flat and can fit closely; the hydrostatic level sensors and vibration acceleration sensors are fixed on the structural surface of the arrangement points with structural adhesive. Before bonding, a primer shall be brushed on the arrangement surface to improve the bonding adhesion. After the sensors are fixed, a protective shell with anti-smash and waterproof functions shall be installed to avoid damage caused by contact of personnel and equipment during operation. Meanwhile, eye-catching signs shall be set around the monitoring points to prevent damage to sensors and signal cables caused by construction or operation operations; the automatic monitoring prisms are fixed at the arrangement points by special fixtures, and the fixtures are connected to the structural surface in a non-destructive manner, so as to avoid damaging the reinforcing steel bars and main structure of the existing station structure due to drilling operation.

[0125] After all sensors are arranged, no less than 3 times of independent collection and verification of initial values shall be carried out. Outliers in the initially collected data are eliminated, and the average value of multiple collections is taken as the initial monitoring value, so as to ensure that the collection accuracy and installation position of the sensors meet the preset requirements.

[0126] All the arranged automatic monitoring sensors are connected to the monitoring data acquisition terminal arranged in the equipment room of the existing station through a special signal cable with an electromagnetic shielding layer. The data acquisition terminal realizes data synchronization with the construction control terminal through a special communication link, so as to build a complete real-time monitoring system.

[0127] After the system debugging is completed, the real-time monitoring operation is started. The corresponding acquisition frequency is matched according to the progress of construction procedures. The basic acquisition frequency is adopted to continuously collect monitoring data during non-operation periods, and the acquisition frequency is increased during key operation periods such as drilling, deviation correction, coring and cutting, so as to realize uninterrupted real-time acquisition of three parameters, namely settlement, horizontal displacement and vertical vibration acceleration of the existing station structure. During the acquisition process, the data acquisition terminal preprocesses the real-time collected raw data, eliminates abnormal jump data by means of threshold filtering and trend fitting, and synchronously transmits effective monitoring data to the construction control terminal in real time, so as to form continuous monitoring data curves and monitoring reports, and realize full-process real-time tracking of the state of the existing station structure.

[0128] Based on current regulations and existing station operation and control standards, pre-set graded early warning thresholds for the three monitoring parameters of settlement, horizontal displacement, and vertical vibration acceleration, with dual control of cumulative change and rate of change. The early warning levels are divided into four levels, from low to high: blue warning, yellow warning, orange warning, and red warning. A blue warning corresponds to the measured value reaching 70% of the control value, a yellow warning corresponds to the measured value reaching 80% of the control value, an orange warning corresponds to the measured value reaching 90% of the control value, and a red warning corresponds to the measured value reaching or exceeding the control value.

[0129] The construction control terminal incorporates a tiered early warning algorithm, which automatically determines the early warning level based on real-time monitoring data, triggers corresponding early warning prompts, and simultaneously pushes the early warning information to relevant on-site construction management, supervision, and operation and maintenance units, forming a closed-loop control process of monitoring-early warning-response. The entire process of monitoring data collection, processing, and early warning recording is maintained using a dual storage mode of local servers and cloud backups, with a retention period of no less than 3 years after project completion, meeting the requirements for project archiving.

[0130] During real-time monitoring, manual routine inspections are carried out simultaneously with automated monitoring. The focus is on checking whether new cracks or leaks have appeared in the existing station structure, whether the monitoring points are intact, whether there is any damage to the sensors and cables, and whether there are any interfering factors in the monitoring environment that may affect the accuracy of the monitoring data. Daily inspection records are generated and cross-validated with automated monitoring data to ensure a comprehensive grasp of the structural status of the existing stations.

[0131] In one or more embodiments of the present invention, during the core cutting operation of the angle steel and gusset plate of the lattice column: when drilling into the concrete section of the existing station pile, the power head speed is set to 70 r / min; when the drill bit touches the angle steel and gusset plate of the lattice column, the power head speed is switched to 35 r / min.

[0132] Specifically, before starting the core cutting operation, the speed output accuracy of the crawler drilling rig's power head can be calibrated on-site. Using a contact speed tester, at least three independent speed tests are conducted on the two preset operating speeds of 70 r / min and 35 r / min. The actual output speed of each speed is recorded, and the deviation between the actual speed and the set speed is controlled within the allowable range specified in the standard, thus completing the accuracy calibration of the two operating speeds. At the same time, a speed switching trigger logic is preset in the construction management terminal, which is linked to the collection of real-time data on the rotational torque, feed pressure, and drilling depth of the crawler drilling rig's power head. This data is then matched with the pre-calibrated design depth range of the existing station pile concrete section, lattice column angle steel, and gusset plate to provide a basis for speed switching.

[0133] After calibration and presetting, the crawler drilling rig was started to carry out core cutting operations. By analyzing the characteristics of torque and feed pressure changes during the trial drilling process, and combining this with drilling depth data, it was confirmed that the core drill bit had entered the concrete section of the existing station pile. The operating speed of the crawler drilling rig's power head was then stably set to 70 r / min, the speed setting was locked, and a constant feed pressure and circulating flushing fluid flow rate adapted to this speed were matched to conduct continuous, uniform cutting operations. The stability of the power head's speed was monitored in real time during the operation. If the speed fluctuation exceeded the preset range, the drill bit feed was paused, and the factors affecting speed stability were investigated and eliminated before resuming operations. This speed setting is suitable for the crushing requirements of the concrete section, ensuring efficient concrete cutting and crushing while controlling the vibration amplitude generated by the cutting operation, reducing disturbance to the surrounding strata of the existing station pile.

[0134] During concrete section cutting operations, the construction control terminal collects real-time data on the power head's rotation torque, feed pressure, and drilling depth at a fixed frequency. If a sudden increase in rotation torque or a feed pressure fluctuation exceeding the preset range is detected, and the drilling depth matches the pre-calibrated design depth range for the lattice column angle steel and gusset plates, the drill bit feed is immediately paused. The power head rotates at a low speed to verify the drilling depth and cutting end face position, confirming that the core drill bit's cutting end face has contacted the lattice column's angle steel and gusset plates. After confirmation, the power head rotation is stopped, and the crawler drilling rig's power head operating speed is smoothly switched from 70 r / min to 35 r / min. After the speed switch is complete, the power head rotation is restarted to avoid drill bit chipping, jamming, or cutting impact caused by sudden speed changes.

[0135] After the speed switch is completed, lock the working gear of 35r / min on the power head, match the uniform feed speed and circulating flushing fluid pressure that are suitable for this speed, and carry out a smooth grinding and cutting operation on the angle steel and gusset plates of the lattice column. During the operation, continuously monitor the changes in rotational torque and feed pressure, and continuously discharge the steel chips and concrete debris generated by cutting out of the channel through the circulating flushing fluid to avoid the accumulation of chips on the cutting end face and affect the continuity of the operation.

[0136] After each preset cutting depth is completed, the drill bit feed is paused to check the progress of the cutting operation. Only after confirming that the cut surfaces of the angle steel and gusset plates are complete and that there are no uncut areas remains, can the operation continue. This speed setting is adaptable to the operational requirements of steel cutting. Low-speed, stable grinding reduces impact vibration during the cutting process, minimizing disturbance to the existing station structure. It also prevents chipping or breakage of cutting teeth, ensuring the continuity of the cutting operation.

[0137] This invention addresses the core shortcomings of existing horizontal drilling techniques, such as cumbersome correction procedures, insufficient accuracy in borehole axis control, and significant construction disturbances. By precisely controlling the dual-phase state of shape memory alloy drill rods, it achieves in-situ dynamic and precise correction during horizontal drilling. The austenitic phase of the drill rod is maintained throughout the drilling process to ensure directional stability. When axis deviation occurs, the phase switching and attitude adjustment of the drill rod can be completed simply by local cooling and heating of the deviated section, eliminating the need for frequent tripping and re-drilling to replace specialized correction tools. This significantly simplifies the correction process and avoids borehole wall and formation disturbances caused by frequent tool disassembly and assembly, effectively improving the accuracy of borehole axis control and ensuring the accuracy of the lattice column cutoff position. Furthermore, the directional casing is simultaneously advanced during drilling to form a stable... With fixed duct support, a complete core sampling channel is directly formed after the shape memory alloy drill rod is extracted, realizing a smooth connection between directional drilling and core cutting processes. Combined with precise positioning of the core cutting operation, the complete severing of the lattice column is achieved. After the core is taken out, backfilling and grouting are carried out through the duct formed by the directional casing, which further ensures the stability of the stratum after the operation. The entire operation does not require demolition of the existing station main structure, which greatly reduces the impact of construction vibration and stratum disturbance on the existing operating station structure. It can fully meet the stringent requirements of operating stations for construction accuracy and deformation control, effectively avoid the adverse effects of construction on the safety of train operation, and improve the construction accuracy, operation efficiency and construction safety of horizontal severing of lattice columns in existing stations.

[0138] The above is the overall concept of the present invention. For ease of understanding, the present invention also provides the following embodiments:

[0139] Reference Figures 1 to 4 This embodiment takes the tunnel section between Dongfeng Station and Guangtong Road Station of Wuxi Metro Line 6 passing under the existing Dongfeng Station as the background. The newly built shield tunnel section of this project needs to pass under the existing operating station. The column piles constructed in advance of the existing station intrude into the limit of the newly built shield tunnel, and the pile body and internal grid columns of the intruding section need to be pre-cut horizontally.

[0140] This embodiment involves existing column piles with a diameter of 1.2m. A 600mm × 600mm steel lattice column is installed inside the pile body, with angle steel specifications of 200mm × 200mm × 24mm. The top of the lattice column is rigidly connected to the existing station floor slab. The designed cut-off elevation is 5.2m vertically away from the existing station floor slab, and the horizontal drilling distance between the drilling rig working face and the column pile is 8m. The specific implementation process is as follows:

[0141] Step 1: Construction of the construction platform and determination of the horizontal drilling direction

[0142] Before the operation, the existing Dongfeng Station's structural as-built drawings, column piles, and lattice column construction data were retrieved. The thickness of the existing station's base slab and the dimensions of the track bed structure were verified on-site. Ground-penetrating radar, combined with borehole detection, was used to verify the actual burial depth, cross-sectional dimensions, and precise three-dimensional spatial coordinates of the lattice columns. It was confirmed that there were no existing underground pipelines, structures, or other obstacles within the horizontal drilling path, and the target cut-off area of ​​the lattice columns was clearly defined. In the end shaft of the newly built tunnel section, a pit-type construction platform was excavated at the location of the column piles to be treated. The excavation depth of the platform strictly matched the design cut-off elevation of the lattice columns, ensuring that the elevation of the platform's working surface was consistent with the center point of the lattice column to be cut off. A 12cm thick layer of C20 concrete was poured and hardened at the bottom of the platform, and the slope was sealed with sprayed concrete of the same grade. Drainage blind ditches were set up around the bottom of the platform to ensure that the working surface was dry and stable.

[0143] After setting up verified coordinate control points in the stable area of ​​the construction platform, a total station was set up to complete the station setup and backsight orientation. The center coordinates of the top, bottom, and cut-off positions of the lattice column were independently verified three times using the total station. The average value was taken as the accurate center coordinates of the cut-off position. Combined with the actual axis data of the column pile verified on site, the horizontal drilling direction perpendicular to the axis of the column pile was determined. The drilling baseline and drilling reference point were marked on the construction platform. The HDL-180D1 crawler drilling rig was hoisted to the drilling reference point. The horizontal rotation angle and elevation angle of the drilling rig slide were adjusted (adjustment range -12° to 90°). Through real-time tracking and measurement using the total station, the center line of the drilling rig's power head was made to be on the same horizontal plane as the center point of the lattice column to be cut off and to be completely coincident with the horizontal drilling direction baseline. The drilling rig body was fixed on four sides with steel sections. After verifying that the horizontal drilling direction and the drilling rig attitude matched correctly, the drilling rig slide and traveling mechanism were locked.

[0144] Step 2: Dual-phase controlled horizontal directional drilling and in-situ dynamic correction

[0145] This step applies the dual-phase control technology of the shape memory alloy drill rod in this case. The shape memory alloy drill rod has a hollow structure with three independent cooling medium channels, heating power supply channels, and temperature monitoring channels inside the rod wall. The cooling medium channels are connected to the liquid nitrogen spray device, the heating power supply channels are electrically connected to the segmented electric heating device built into the rod, and the temperature monitoring channels are signal connected to temperature monitoring modules arranged at equal intervals along the axial direction of the rod, which can realize closed-loop control of the phase change of the drill rod.

[0146] The shape memory alloy drill pipe is coaxially assembled by inserting it into a seamless 220mm diameter metal directional casing. An alloy cutting tool adapted for drilling in soil layers is fitted to the front end of the directional casing. The assembled drill bit is then locked to the drill rig's power head, and the drill rig is started, feeding at a constant speed along the determined horizontal drilling direction. During drilling, the temperature of the drill bit body is collected in real time by a temperature monitoring module built into the drill bit, maintaining the drill bit temperature within the austenitic temperature range. This ensures the drill bit remains in the austenitic phase throughout the drilling process. Utilizing the stable shape retention capability of the drill bit in the austenitic phase, vertical deflection and lateral displacement during long-distance horizontal drilling are suppressed. Simultaneously, the directional casing advances synchronously with the drill bit, providing continuous support to the borehole and ensuring borehole wall stability.

[0147] During drilling, the drilling axis coordinates, drilling torque, and feed pressure are collected in real time by the built-in measurement-while-drilling module in the drill pipe. The real-time axis is compared with the preset horizontal drilling direction reference axis. When the deviation of the drilling axis exceeds the preset threshold, the drill string feed is stopped, and the positions of the drill head and directional casing are locked. According to the depth of the offset section, only the control valve of the cooling medium channel corresponding to the offset section is opened, and liquid nitrogen is used to spray circumferentially to locally cool the drill pipe in the offset section. During the cooling process, the temperature of the drill pipe body is monitored in real time until the drill pipe in the offset section has completely switched to the martensitic phase. The drill head lock is released, and the drilling attitude of the drill pipe is adjusted by the drill slide fine-tuning system to correct the axis deviation. After the correction is completed, the drill head is locked again. The drill rod is heated at a constant speed by the electric heating device corresponding to the offset section, and the temperature of the drill rod is monitored in real time until the drill rod in the offset section is completely restored to the austenitic phase. After the lock is released, the drill bit is fed at a preset constant speed until the front end of the directional casing reaches the edge of the column pile. After verifying that the drilling depth, positioning accuracy and axis deviation meet the design requirements, the feed of the drill bit is stopped and the position of the drill rig power head and the directional casing is locked.

[0148] Step 3: Core sampling channel multiplexing and sequential frequency conversion core cutting

[0149] Keeping the directional casing in a fixed position, the shape memory alloy drill rod is uniformly and coaxially pulled out of the directional casing, releasing a complete and unobstructed core sampling channel inside the directional casing. An endoscope is used to inspect the integrity of the casing's inner wall and the stability of the borehole wall, and residual drill cuttings are removed from the casing. A 171mm outer diameter diamond composite core drill bit is then installed. This drill bit has staggered cutting teeth, making it suitable for both concrete breaking and lattice column steel cutting operations. After rigidly connecting the core drill bit to the core sampling drill rod using a threaded coaxial connection, it is locked to the drilling rig's power head. The core drill bit is then smoothly guided along the core sampling channel to the edge of the column pile.

[0150] Six interconnected, partially overlapping core sampling positions were planned within the 1.2m diameter pile body. Numbered 1-6, core sampling was conducted in batches using an intermittent skip-hole technique to avoid excessively large single-cut sections that could lead to instantaneous stress release in the pile body. The odd-numbered holes (1, 3, and 5) were drilled first. Each completed core sampling at a position partially cuts the angle steel of the lattice column, gradually releasing residual stress in the pile body. During the core sampling process, the power head speed was consistently set to 70 r / min when drilling into the concrete section of the pile. When the drill bit touched the angle steel and gusset plates of the lattice column, the power head speed automatically switched to 35 r / min. Simultaneously, the propulsion oil pressure was consistently controlled at 5–6 MPa, and the drive oil pressure was consistently controlled at 8–10 MPa. This low-speed, high-torque mode smoothly cut the steel, avoiding tooth breakage, drill jamming, and severe vibration. After the odd-numbered holes are completed and the grouting in the corresponding holes has initially set, the even-numbered holes No. 2, 4, and 6 will be constructed until all holes are cut, so as to achieve complete physical separation of the entire cross-section of the lattice column and release the rigid connection between the lattice column and the existing station floor slab.

[0151] Step 4: Full-process automated monitoring and duct backfilling grouting

[0152] Throughout the construction process, automated monitoring sensors were deployed at key stress-bearing locations on the existing station's foundation slab, track bed, and sleepers to monitor the settlement, horizontal displacement, and vertical vibration acceleration of the existing station structure in real time. The monitoring data was synchronized to the construction control terminal in real time. Pre-set tiered control thresholds were implemented: the cumulative settlement of the foundation slab should not exceed 3.0 mm, and the cumulative horizontal deformation should not exceed 1.0 mm. When monitoring data showed that the cumulative settlement of the foundation slab reached 2.0 mm, an early warning was triggered, and intervention measures such as slowing down drilling and optimizing grouting parameters were implemented. If the settlement value reached the 3.0 mm control value or the horizontal displacement reached the 1.0 mm control value, work was immediately stopped, and ground reinforcement was implemented.

[0153] After each core drilling operation is completed, the core drill bit and core drilling rod are completely extracted from the directional casing. Immediately afterward, a grouting pipe is inserted into the borehole, and micro-expansion cement grout is used for backfilling. The grouting pressure is controlled at 0.3-0.5 MPa to match the ground pressure in the working area. The grouting follows the principle of equal replacement, and the grouting volume is consistent with the volume of drill cuttings and soil discharged from the core, to fill the ground loss, maintain the local stability of the pile foundation, and prevent additional settlement caused by soil erosion. After the grouting is completed, the borehole opening is sealed.

[0154] Step 5: Verification of the cutoff effect and safe tunnel boring machine crossing

[0155] After all core drilling was completed and the grout reached its design strength, the monitoring data for the entire process was compiled. The maximum cumulative settlement of the existing station floor slab was 2.1 mm, and the maximum horizontal displacement was 0.6 mm, both far below the design control values. No structural cracks, leaks, or other abnormalities were observed. Endoscopic drilling confirmed that the entire cross-section of the lattice column was completely severed, physically severing the rigid force transmission link between the lattice column and the existing station floor slab, achieving the pre-deconstrained design goal. When the tunnel boring machine subsequently advanced to this section, the cutterhead only needed to cut the loosened concrete and low-strength backfill grout, without directly grinding the high-strength steel lattice column, completely avoiding the severe vibrations caused by grinding steel. The cumulative settlement increase of the existing station floor slab during the entire tunneling process was only 0.5 mm, achieving intrinsic safety protection for the existing operating station structure and not affecting the normal operation of the existing line.

[0156] The above provides a detailed description of a method for horizontally truncating the internal lattice columns of existing station piles. Specific examples have been used to illustrate the principle and implementation of this invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for horizontally truncating the internal lattice columns of an existing railway station pile, characterized in that, The method includes: A construction platform is built in the new foundation pit, and the horizontal drilling direction is determined according to the target cut-off area of ​​the existing station lattice column. The shape memory alloy drill rod is drilled along the directional casing in the horizontal drilling direction, and the shape memory alloy drill rod maintains the austenitic phase during the drilling process. When a deviation in the drilling axis is detected, the shape memory alloy drill rod in the off-center section is locally cooled to switch to the martensitic phase. The drilling posture of the shape memory alloy drill rod is adjusted under the martensitic phase to complete the correction. The shape memory alloy drill rod in the off-center section is heated to restore it to the austenitic phase, and drilling continues to the edge of the lattice column pile. The shape memory alloy drill rod is pulled out from the directional casing to release the core sampling channel inside the directional casing; the core drill bit is connected to the core sampling drill rod and then guided along the core sampling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plate of the lattice column. The coring drill bit and the coring operation drill rod are pulled out from the directional casing, and grouting slurry is injected into the channel formed by the directional casing for backfilling grouting.

2. The method according to claim 1, characterized in that, Determining the horizontal drilling direction based on the target cut-off area of ​​the existing station lattice column includes: The center coordinates of the top, bottom and cut-off positions of the lattice column are reverse-layouted and verified using a total station. Based on the verified layout results, the horizontal drilling direction perpendicular to the axis of the existing station pile is determined. Adjust the slide elevation angle and horizontal rotation angle of the crawler drilling rig so that the center line of the power head of the crawler drilling rig is on the same horizontal plane as the center point to be cut off of the lattice column. Use steel sections to fix the crawler drilling rig on four sides after adjustment. After verifying that the horizontal drilling direction matches the drilling rig posture correctly, lock the drilling rig.

3. The method according to claim 2, characterized in that, The process of drilling the shape memory alloy drill rod along the directional casing in the horizontal drilling direction, wherein the shape memory alloy drill rod maintains the austenitic phase during drilling, includes: The shape memory alloy drill rod is inserted into the directional casing to complete coaxial assembly, and the assembled drill bit is locked to the crawler drilling rig's power head. The drill bit is fed at a constant speed along the horizontal drilling direction. During drilling, the temperature of the drill rod body is monitored in real time by the temperature monitoring module built into the shape memory alloy drill rod to maintain the drill rod temperature within the austenitic phase range and preserve the austenitic phase state of the shape memory alloy drill rod. The directional casing is a seamless metal casing, and the front end of the directional casing is equipped with an alloy cutting tool adapted for drilling in soil layers.

4. The method according to claim 3, characterized in that, When a drilling axis deviation is detected, the shape memory alloy drill pipe in the misaligned section is locally cooled to switch to the martensitic phase. The drilling posture of the shape memory alloy drill pipe is then adjusted under the martensitic phase to correct the deviation, including: During the drilling process, the drilling axis coordinates, drilling torque and feed pressure of the shape memory alloy drill rod are collected in real time by the drilling measurement module. When the deviation value between the drilling axis and the preset horizontal drilling direction exceeds the preset threshold, the drill bit feed is stopped and the drill head is locked. The shape memory alloy drill rod in the offset section is locally cooled by circumferential spraying with liquid nitrogen, and the cooling area is controlled to cover only the axial offset section. The temperature of the drill rod body is monitored in real time during the cooling process until the shape memory alloy drill rod in the offset section is completely switched to the martensitic phase. Release the power head lock of the drilling rig, adjust the drilling attitude of the shape memory alloy drill rod through the slide fine adjustment system of the crawler drilling rig, correct the axis deviation, lock the power head of the drilling rig after completing the attitude correction, and check that the drilling axis deviation value has fallen back to within the preset threshold.

5. The method according to claim 4, characterized in that, The process of heating the offset section shape memory alloy drill rod to restore it to the austenitic phase and continuing drilling to the edge of the lattice column pile includes: The shape memory alloy drill rod in the offset section is heated at a constant rate by the built-in electric heating device. The temperature of the drill rod body is monitored in real time during the heating process until the shape memory alloy drill rod in the offset section is completely restored to the austenitic phase. After rechecking that the drilling axis is consistent with the horizontal drilling direction, the drilling rig power head is unlocked, and the drill bit is fed at a preset uniform speed. During the drilling process, the drilling depth and the position of the drill bit front end are monitored in real time until the front end of the directional casing reaches the edge of the existing station pile. After verifying that the drilling depth, positioning accuracy and axis deviation meet the design requirements, the drill bit feed is stopped, and the drilling rig power head and the position of the directional casing are locked.

6. The method according to claim 5, characterized in that, The step of extracting the shape memory alloy drill rod from the directional casing and releasing the core sampling channel inside the directional casing includes: Disassemble the connecting joint of the shape memory alloy drill rod section by section in a reverse mode; completely extract the shape memory alloy drill rod from the directional sleeve in a uniform speed coaxial mode; After the drill pipe is completely extracted, an endoscope is used to inspect the integrity of the inner wall of the directional casing and the stability of the borehole wall. The remaining drill cuttings inside the casing are removed, and a complete and unobstructed core sampling channel is released inside the directional casing.

7. The method according to claim 6, characterized in that, The process of connecting the core drill bit to the core drilling rod and guiding it along the core drilling channel to the edge of the lattice column pile body to perform core cutting on the angle steel and gusset plates of the lattice column includes: After the core drill bit and the core drilling rod are rigidly connected by a threaded coaxial connection, they are locked to the power head of the crawler drilling rig; the core drill bit is smoothly guided along the core drilling channel until the core drill bit reaches the edge of the lattice column pile body; After starting the drilling rig for trial operation and confirming that the drilling tools are operating normally, core cutting operations are carried out on the angle steel and gusset plates of the lattice column. The core cutting bit is a diamond composite core cutting bit, and the cutting teeth of the core cutting bit are arranged in an alternating manner to adapt to concrete breaking and lattice column steel cutting operations.

8. The method according to any one of claims 1 to 7, characterized in that, The shape memory alloy drill rod has a hollow structure. Inside the rod body are independent cooling medium channels, heating power supply channels, and temperature monitoring channels. The cooling medium channels are connected to a liquid nitrogen spray device for precise local cooling of the misaligned section of the drill rod. The heating power supply channel is electrically connected to an internal electric heating device for uniform heating of the misaligned section. The temperature monitoring channel is signal-connected to an internal temperature monitoring module for real-time acquisition of the drill rod's body temperature, enabling closed-loop control of phase changes.

9. The method according to claim 8, characterized in that, The method also includes: installing automated monitoring sensors on the stress-bearing parts of the existing station floor, track bed and sleepers to monitor the settlement, horizontal displacement and vertical vibration acceleration of the existing station structure in real time.

10. The method according to claim 9, characterized in that, During the core cutting operation of the angle steel and gusset plates of the lattice column: when drilling into the concrete section of the existing station pile, the power head speed is set to 70 r / min; when the drill bit touches the angle steel and gusset plates of the lattice column, the power head speed is switched to 35 r / min.

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