A method for bedrock and boulder pretreatment for large-section rectangular pipe jacking

Abstract

This invention discloses a method for pretreatment of bedrock and boulders in large-section rectangular pipe jacking, comprising at least: micro-jacking rock crushing and mud-pressing retreat. Micro-jacking rock crushing includes at least constructing a pretreated borehole wall; installing a water-stopping device; micro-jacking, pipe installation, rock crushing, and slag removal, jacking to a predetermined length; mud-pressing retreat includes at least preparing composite thick mortar; injecting composite thick mortar into the front of the micro-jacking machine in the borehole to compress and fill the stratum voids and generate a certain reaction force to form an overpressure sealed environment; the mud-pressing reaction force and the pull-back force jointly resist the pipe-retreating friction, thereby making the steel pipe and micro-jacking machine easily pulled back under the action of the pull-back device, with mud-pressing and pull-back occurring simultaneously; the pretreated borehole is completely filled with composite thick mortar, and the micro-jacking machine is withdrawn and the borehole is sealed, completing the pretreatment of the current borehole. This method effectively replaces the rock strata with treated strata suitable for rectangular pipe jacking machine cutting and excavation, offering a large construction coverage area, safety, efficiency, and controllable settlement.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology, and in particular to a method for pretreatment of bedrock and boulders in large-section rectangular pipe jacking. Background Technology

[0002] With the continuous development of my country's economy and society and the acceleration of urbanization, problems such as traffic congestion, parking difficulties, insufficient station layout, land scarcity, and high demolition costs in existing urban areas have become increasingly prominent due to inadequate early planning and insufficient forecasting of urban economic development. The development of urban underground space using the green, safe, efficient, and low-cost mechanical rectangular pipe jacking excavation technology has become a key method for solving these problems.

[0003] Mechanical rectangular pipe jacking excavation technology is suitable for soft clay to gravelly soils, such as silt, silty clay, cohesive soil, silt, gravelly soil (silt-gravel), cobble gravel soil, and soft rock (less than 5 MPa). Based on current domestic rectangular pipe jacking equipment manufacturing technology and construction experience, rectangular pipe jacking equipment cannot be used normally in geological conditions such as strongly to moderately weathered rock strata with high saturated uniaxial compressive strength, or isolated boulders. Currently, when rectangular pipe jacking encounters bedrock strata, the rock within the pipe jacking section is pre-crushed before jacking construction. The existing technology is to use a horizontal anchor drilling rig to drill through the hard rock intruding into the pipe jacking tunnel, and then fill it with mud after enlarging the excavation diameter of the pipe jacking machine cutterhead. However, this method has the following problems: (1) The construction length of the horizontal anchor drilling rig is limited. When the length exceeds 30m, the construction accuracy cannot be guaranteed. Moreover, the higher the strength of the weathered rock, the more likely it is to cause hole drift and the more difficult it is to control the attitude. If the corner of the isolated rock is encountered, the attitude will drift upward or the hole will drift more seriously, so the pretreatment effect cannot be fully achieved; (2) There is sandy soil with abundant groundwater within the crossing section. This method is prone to cause stratum loss and ground subsidence during pretreatment construction; (3) As the rectangular pipe jacking section becomes larger, the number of horizontal anchor drilling holes will increase, making construction cumbersome and the construction period long. In addition, bedrock or boulders between the horizontal holes in the "honeycomb" pattern cannot be treated; (4) after the horizontal anchor bolts are pretreated, the diameter of the cutter head of the rectangular pipe jacking machine needs to be increased, which adds extra cost. If the rectangular pipe jacking machine encounters bedrock protrusion during the jacking process, it is necessary to retract the rectangular pipe jacking machine and then remodel and enlarge the cutter head. The risk of retracting the rectangular pipe jacking machine with such a large cross section is high and the cost is high, so the method has no cost advantage overall.

[0004] Therefore, this invention proposes a bedrock and boulder pretreatment method that is highly adaptable to rock formations, has a large pretreatment coverage area and high precision, is simple and fast in construction, causes little disturbance to the formation, is safer to construct, has controllable settlement, and has low overall cost. Summary of the Invention

[0005] This invention provides a method for pre-treatment of bedrock and boulders for large-section rectangular pipe jacking, in order to solve the technical problems of low overall accuracy of bedrock treatment, incomplete pre-treatment, weak adaptability to strata, and long and cumbersome construction period in the prior art.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for pretreatment of bedrock and boulders in large-section rectangular pipe jacking, comprising at least:

[0007] Microjacking rock breaking and mud backing;

[0008] The micro-jacking rock crushing process includes at least: constructing a pre-treated borehole wall; installing a water-stopping device; jacking in the micro-jacking machine, installing steel pipe sections, crushing the rock, and removing slag, until the preset length has been reached;

[0009] The mud pressing and retraction process includes at least: preparing composite thick mortar; injecting composite thick mortar into the front of the micro jacking machine in the pre-treated hole to squeeze and fill the formation voids; creating an overpressure sealed environment in front of the micro jacking machine head in the hole through the reaction force generated by the injection of composite thick mortar; using a pullback device to pull back the steel pipe along with the micro jacking machine, so that the mud pressing reaction force and the pullback force jointly resist the frictional resistance generated when the steel pipe and the micro jacking machine retract, wherein the mud pressing and pullback steps are synchronized; until the pre-treated hole is completely filled with composite thick mortar and the micro jacking machine is completely withdrawn and the hole is sealed, thus completing the rock treatment of the current pre-treated hole.

[0010] As a preferred embodiment, before constructing the pre-treated opening wall, the following steps are also included:

[0011] Horizontal geological boreholes are drilled to determine the distribution and strength of bedrock or boulders, and to check the soil reinforcement effect and water leakage in the portal reinforcement area of ​​the large-section rectangular jacking pipe to be excavated.

[0012] As a preferred embodiment, after inspecting the soil reinforcement effect and water leakage in the portal reinforcement zone of the large-section rectangular pipe jacking area to be excavated, the method further includes:

[0013] Based on the distribution of bedrock or boulders and the cutterhead cutting blind zone of the large-section rectangular pipe jacking machine, the layout scheme of the pre-treatment holes is determined; wherein, the pre-treatment holes should completely cover the rectangular pipe jacking machine cross-section and the cutterhead cutting blind zone affected by bedrock or boulders, and the length of the pre-treatment holes should at least extend through the identified bedrock or boulders area.

[0014] As a preferred embodiment, the construction of the pre-treated opening wall specifically includes:

[0015] Based on the layout range of each pretreatment hole, determine the opening size of each pretreatment hole, and construct a plain concrete opening wall at the reserved opening in the excavation range of the large-section rectangular jacking pipe.

[0016] As a preferred embodiment, the installation of the water-stopping device specifically includes:

[0017] Once the opening wall reaches its designed strength, water drilling is used to cut the plain concrete within the opening area and the reinforced concrete foundation pit retaining structure in front of the opening. A water-stopping device for micro pipe jacking machine construction is then installed at the pretreated opening.

[0018] As a preferred embodiment, the micro-jacking machine jacks up, loads steel pipe sections, crushes rock, and removes slag until it has jacked to the preset length, specifically as follows:

[0019] The micro-jacking machine is gradually pushed into the pre-treatment hole to be processed, thereby cutting and breaking the rock during the jacking process. The broken rock is discharged through the mud-water circulation system, and steel pipe sections are installed at the same time to replace the cut and broken rock strata until the preset length of the pre-treatment hole is reached.

[0020] As a preferred embodiment, the preparation of composite thick mortar involves: injecting composite thick mortar into the front of the micro-jacking machine in the pre-treated hole to compress and fill the formation voids; the reaction force generated by the injection of composite thick mortar creates an overpressure sealed environment in front of the micro-jacking machine head in the hole; and using a pullback device to pull back the steel pipe along with the micro-jacking machine, so that the mortar injection reaction force and the pullback force jointly resist the frictional resistance generated when the steel pipe and the micro-jacking machine retract. The mortar injection and pullback steps are synchronized; this continues until the pre-treated hole is completely filled with composite thick mortar and the micro-jacking machine is completely withdrawn and the hole is sealed, thus completing the rock treatment of the current pre-treated hole. Specifically:

[0021] After the micro-jacking machine pushes the current pre-treated hole to a preset length, composite thick mortar is prepared and injected into the front of the micro-jacking machine breast plate in the current pre-treated hole through the grouting hole reserved on the cutter head to squeeze and fill the formation voids.

[0022] During the process of injecting composite mortar, the reaction force generated by injecting composite mortar creates an overpressure sealed environment in front of the machine head in the hole. Then, the steel pipe section along with the micro pipe jacking machine can be easily pulled back using the pullback device. This allows the mortar injection reaction force and the pullback force to jointly resist the frictional resistance generated when the steel pipe and the micro pipe jacking machine retract. The mortar injection and pullback steps are synchronized.

[0023] The steps of pressing and pulling back are repeated, until the entire space of the pre-treated hole is filled with composite thick mortar.

[0024] As a preferred option, it also includes:

[0025] As the micro-jacking machine is gradually squeezed by the composite thick mortar and retracted to the current pre-treated hole opening under the action of the pullback device and fully received, the opening of the current pre-treated hole is sealed with bricks or steel plates.

[0026] As a preferred option, after completing the bedrock or boulder treatment of the current pre-treated hole, the following is also included:

[0027] The remaining pre-treated holes were then subjected to micro-jacking rock crushing and mud compaction retreat.

[0028] As a preferred option, after micro-jacking rock fracturing and mud removal in all pre-treated holes, the rock formation is replaced with a treated formation suitable for rectangular pipe jacking machine cutting and excavation, specifically including:

[0029] The pre-treatment hole construction equipment was removed and the damaged structure inside the working well was repaired. A water-stopping device for rectangular pipe jacking construction was installed at the reserved portal of the large-section rectangular pipe jacking range to be excavated. The rectangular pipe jacking machine was installed and debugged, so that the large-section rectangular pipe jacking machine could smoothly advance and construct in the treated strata until the tunnel was completed.

[0030] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0031] The technical solution of this invention combines micro-jacking rock breaking and mud-pressing retreat. The micro-jacking construction quickly and efficiently breaks the bedrock or boulders within the excavation range of the large-section rectangular jacking pipe, reducing the strength and size of the rock. Then, mud-pressing retreat is carried out, that is, composite thick mortar is injected in front of the micro-jacking machine in the pre-treated hole to squeeze and fill the voids in the strata. At the same time, the injection of composite thick mortar can generate a certain reaction force and form an overpressure sealed environment in front of the micro-jacking machine head in the hole. Then, the steel pipe and the micro-jacking machine are pulled back using a pullback device. The mud-pressing reaction force and the pullback force jointly resist the frictional resistance generated when the steel pipe and the micro-jacking machine are pulled back. The mud pressing and pullback are synchronized. Inject the same or even a larger volume of composite mortar into the cavity created by the pullback, so that the injected composite mortar generates a certain reaction force to facilitate the retraction of the micro-jacking machine and steel pipe section under the action of the pullback device. The mortar injection and pullback are repeated until the pre-treated hole is completely filled by the composite mortar and the micro-jacking machine is completely withdrawn and the hole is sealed.

[0032] By combining the two technologies mentioned above, the rock strata are effectively replaced with low-strength treated strata suitable for rectangular pipe jacking machine cutting and excavation. This method allows for unlimited pretreatment length, larger coverage area, fewer pretreatment operations, effectively reducing disturbance to the strata, and controllable ground settlement. It ensures that during subsequent large-section rectangular pipe jacking construction in soft-over-hard strata with bedrock or boulders, the jacking posture is controllable and less prone to deflection. The cutterhead experiences relatively uniform stress, reducing cutterhead excavation torque, facilitating smooth auger excavation, and ensuring a smooth and safe jacking process.

[0033] Furthermore, the technical solution of the present invention has strong adaptability to different strata such as bedrock or boulders, large pretreatment coverage area, simple construction process, fast construction speed, cost saving, small disturbance to the strata during construction, safer construction, and controllable settlement. In addition, the rock in the pretreatment hole is crushed by a micro pipe jacking machine, making the construction process efficient and safe. Compared with the prior art, it is not necessary to expand the diameter of the rectangular pipe jacking machine cutter head after the horizontal anchor bolt pretreatment, so the economic benefits of the present invention are obvious. Attached Figure Description

[0034] Figure 1 : This is a flowchart illustrating the steps of a method for pre-treating bedrock and boulders in a large-section rectangular pipe jacking project according to an embodiment of the present invention;

[0035] Figure 2 : A schematic diagram of the distribution of horizontal geological boreholes provided in an embodiment of the present invention;

[0036] Figure 3 : This is a schematic diagram of the pre-treatment hole layout provided in an embodiment of the present invention;

[0037] Figure 4 : A schematic diagram of the construction of a concrete opening wall provided in an embodiment of the present invention;

[0038] Figure 5 This is a schematic diagram of a pre-treated hole drilling machine core sampling method provided in an embodiment of the present invention.

[0039] Figure 6 : A schematic diagram of the construction of the pre-treated hole water-stopping device provided in an embodiment of the present invention;

[0040] Figure 7 : A schematic diagram of the construction of each pre-treated hole provided in the embodiment of the present invention;

[0041] Figure 8 : A schematic diagram of the jacking operation of a miniature pipe jacking machine provided in an embodiment of the present invention;

[0042] Figure 9 : This is a schematic diagram of the retraction of the miniature pipe jacking machine provided in an embodiment of the present invention;

[0043] Figure 10 : This is a schematic diagram of the mud-pressing retraction of a micro-pipe jacking machine provided in an embodiment of the present invention;

[0044] Figure 11 : A schematic diagram of the receiving and sealing of a miniature pipe jacking machine provided in an embodiment of the present invention;

[0045] Figure 12 : A schematic diagram of the repair of a large-section rectangular pipe jacking tunnel provided in an embodiment of the present invention;

[0046] Figure 13: This is a schematic diagram of the arrangement of the large-section rectangular jacking pipe water-stopping device provided in an embodiment of the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] This invention provides a method for pre-treating bedrock and boulders in large-section rectangular pipe jacking. Specifically, in its implementation, this method primarily involves pre-treating the bedrock or boulders within the area traversed by a large-section rectangular pipe jacking machine. When a large-section rectangular pipe jacking machine (hereinafter referred to as "large pipe jacking machine") encounters bedrock or boulder strata, the following situations may occur: 1) Due to the significant difference in strength between the rock and soil, tunneling in such strata (soft above, hard below) can lead to uneven stress on the cutterhead, easily causing significant changes in the jacking axis and posture; 2) High-strength rock can easily cause significant wear on the cutterhead and further lead to the machine seizing up; 3) Large boulders can easily jam the cutterhead and block the spiral exit, all of which can lead to the failure of the large pipe jacking. Therefore, to avoid these situations during tunnel excavation, pre-treating the bedrock or boulders before the large pipe jacking machine begins operation is essential.

[0049] Existing bedrock pretreatment technologies have many problems. This invention employs a miniature pipe jacking machine capable of tunneling in bedrock or boulder strata with a rock strength exceeding 40 MPa to break up the rock. Then, composite mortar is injected to compress and fill the strata. The reaction force generated in front of the miniature pipe jacking machine head within the borehole and the pulling force generated by the pullback device resist the frictional resistance of the steel pipe section and the miniature pipe jacking machine during retraction, ultimately resulting in the complete replacement of the rock strata by the composite mortar. This pretreatment method effectively controls ground subsidence and ensures the smooth implementation of subsequent large-section rectangular pipe jacking. Among them, the micro-tube jacking machine has the characteristics of efficiently breaking bedrock or boulders with high rock strength. The jacking construction length is unlimited, the coverage area is large, the hole is not prone to deviation, the posture is controllable, and the construction accuracy is guaranteed. It adopts the green, safe, environmentally friendly and efficient slurry balance jacking method. The construction causes little disturbance to the strata, the ground settlement is controllable, the impact on the surrounding environment is small, and the process is simple and fast. The pre-treated strata excavated by the micro-tube jacking machine are filled with composite thick mortar. That is, while injecting composite thick mortar, the steel pipe section is pulled back along with the micro-tube jacking machine under the combined action of the reaction force generated by the injection of composite thick mortar and the pull force generated by the pull-back device. The mortar injection and pull-back are synchronized until the pre-treated hole is completely filled with composite thick mortar. The micro-tube jacking machine is completely withdrawn and received. This process causes little disturbance to the strata and makes the ground settlement controllable. The treated strata can adapt to the cutting and excavation of the cutterhead of the large-section rectangular tube jacking machine, so as to optimize and improve the existing bedrock pretreatment technology.

[0050] Example 1

[0051] Please refer to Figure 1 The bedrock and boulder pretreatment method for a large-section rectangular pipe jacking project provided by this invention includes at least the following steps S101-S102:

[0052] Step S101: Micro-jacking rock breaking.

[0053] The rock breaking process of the micro-jacking pipe includes at least steps S201-S203:

[0054] S201: Construct pre-treatment wall for hole 3.

[0055] As a preferred embodiment, before constructing the pre-treated hole 3 opening wall, the following is further included:

[0056] Horizontal geological boreholes are drilled to determine the distribution and strength of bedrock or boulders, and to check the soil reinforcement effect and water leakage in the portal reinforcement area of ​​the large-section rectangular jacking pipe to be excavated.

[0057] In this embodiment, please refer to Figure 2Based on the existing geological survey report, several horizontal boreholes 4 will be drilled within the portal area of ​​the large pipe jacking machine to determine the thickness and undulation of the bedrock or boulders, further obtain the engineering properties of the bedrock, and assess its impact on the jacking of the large-section rectangular pipe. At the same time, the reinforcement effect and leakage of the soil in the reinforced area at the reserved portal of the large-section rectangular pipe will be checked. If a large area of ​​water leakage occurs, supplementary reinforcement is required.

[0058] Furthermore, the horizontal boreholes 4 are laid out from bottom to top. When the core samples exposed by the horizontal boreholes 4 in the same row are all free of bedrock, the construction of the upper row of horizontal boreholes 4 is stopped. The horizontal boreholes 4 are constructed using a horizontal coring drill, and preferably, the borehole diameter is Φ108mm.

[0059] Please see Figure 2 In another embodiment, three rows of horizontal boreholes 4 are deployed. Core samples from the lower two rows of horizontal boreholes 4 revealed bedrock and large-diameter boulders, but the uppermost row of horizontal boreholes 4 barely revealed bedrock. Therefore, the pretreatment range for bedrock or boulders is defined vertically as the elevation of the uppermost row of horizontal boreholes 4, extending down to the bottom elevation of the pre-reserved portal steel ring 1 of the large-section rectangular jacking pipe, and horizontally as the edge line of the pre-reserved portal steel ring of the large-section rectangular jacking pipe, which is the deployment range of the pretreatment boreholes 3. The vertical spacing between the horizontal boreholes is 1.0m to 1.5m, and three to five horizontal boreholes 4 can be arranged in the same row, with the spacing determined according to the cross-sectional dimensions of the large-section rectangular jacking pipe.

[0060] As a preferred embodiment, after checking the soil reinforcement effect and water leakage in the portal reinforcement zone of the large-section rectangular pipe jacking area, the method further includes:

[0061] Based on the distribution of bedrock and boulders, and combined with the arrangement of the cutterhead of the large-section rectangular pipe jacking machine and the cutterhead cutting blind zone, the layout scheme of the pretreatment holes 3 is determined; wherein, the pretreatment holes 3 should completely cover the rectangular pipe jacking machine cross-section affected by bedrock and the cutterhead cutting blind zone, and the length of the pretreatment holes 3 should at least penetrate the identified bedrock area.

[0062] In this embodiment, as exemplarily provided, please refer to Figure 3 Based on the thickness and undulation of the bedrock and boulders, pretreatment holes 3 are reasonably arranged at the portal of the large-section rectangular jacking tunnel according to the principle of bottom to top, and the position, spacing and number of pretreatment holes 3 are determined.

[0063] It should be noted that because the cutting range 21 of the cutterhead of the large pipe jacking machine is circular, a cutterhead cutting blind zone 22 will exist when performing large cross-section cutting of rectangular or near-rectangular sections. The pre-treatment hole 3 is constructed using a slurry-balanced micro-pipe jacking machine with rock-breaking capabilities, and its inner diameter should preferably be DN600 to DN1200 mm. The pre-treatment area must completely cover the large-section rectangular pipe jacking machine cross-section affected by bedrock and boulders, as well as the cutterhead cutting blind zone 22.

[0064] In this embodiment, the length of the pretreatment hole 3 is determined based on the distribution of bedrock and boulders. Pretreatment can be carried out from the side with a larger distribution range of bedrock and boulders, or it can be carried out from the starting and receiving shaft entrances of the rectangular jacking pipe, depending on the distribution of bedrock and boulders. Simultaneously, the length of the pretreatment hole 3 must at least penetrate the corresponding distribution range of bedrock and boulders.

[0065] As a preferred embodiment, the construction of the pre-treated hole 3 opening wall specifically involves:

[0066] Based on the layout range of each pretreatment hole 3, determine the opening size of each pretreatment hole 3, and construct a plain concrete opening wall at the reserved opening in the excavation range of the large-section rectangular jacking pipe.

[0067] It should be noted that in this embodiment, please refer to... Figure 4 Based on the layout range of the pre-treatment holes 3, a concrete retaining wall 7 is constructed within the water-stop steel ring of the large-section rectangular jacking tunnel entrance and closely attached to the working shaft retaining structure as the opening structure of the pre-treatment holes 3. The height of the concrete retaining wall 7 should exceed the top of the opening of the pre-treatment holes 3 by 20cm to 30cm. In addition, several temporary steel supports 5 need to be constructed above the concrete retaining wall 7 to support the water-stop steel ring 1 pre-embedded within the range of the large-section rectangular jacking tunnel opening.

[0068] In this embodiment, a reinforcing bar 6 is provided between the concrete retaining wall 7 and the retaining structure piles of the working well to improve the overall stability of the retaining wall. The tie bar 6 is arranged circumferentially along the concrete retaining wall and must be placed outside the construction influence range of the pre-treated hole 3.

[0069] S202: Install water-stopping device 33.

[0070] As a preferred embodiment, the installation of the water-stopping device 33 specifically includes:

[0071] Once the opening wall reaches the design strength, the concrete retaining wall 7 within the opening range of the pre-treated hole 3 and the reinforced concrete foundation pit retaining structure in front of the opening are cut using a water drill, and a water-stopping device 33 for the construction of a micro pipe jacking machine is installed at the opening of the pre-treated hole 3.

[0072] In this embodiment, please refer to Figure 5 and Figure 6A small drilling rig is used to continuously drill along the circular outline of the pre-treated hole 3, extracting core samples of the concrete retaining wall 7, the pre-embedded water-stop steel ring (partial) of the large-section rectangular jacking pipe portal, and the retaining structure within that area. After drilling and cutting, the core sample 31 from the hole is removed. Then, the portal of the pre-treated hole 3 is leveled, and bolt holes 10 are drilled around the small portal within the jacking range of the micro jacking machine. The micro jacking pipe water-stop portal steel plate 32, rubber curtain, and pressure plate are then installed sequentially and fixed with expansion bolts, completing the water-stop device 33 for the construction of the micro jacking machine in the pre-treated hole 3. The drilling diameter of the small drilling rig should preferably be Φ100mm.

[0073] In another embodiment, when the drilling rig is breaking through the well, temporary sealing materials need to be prepared at any time in the well to seal the micro jacking hole 34, so as to prevent water and soil outside the hole from flowing into the working well from the borehole.

[0074] S203: Miniature pipe jacking machine jacks in, loads steel pipe sections, crushes rocks, and removes slag until the preset jacking length is reached.

[0075] As a preferred embodiment, the micro-jacking machine jacks up, loads steel pipe sections, crushes rocks, and removes slag until it has jacked to a preset length, specifically as follows:

[0076] The micro-jacking machine is gradually pushed into the pre-treatment hole 3, thereby cutting and breaking the rock during the jacking process. The broken rock is discharged through the mud-water circulation system, and steel pipe sections are installed simultaneously to replace the cut and broken rock strata until the preset length of the pre-treatment hole 3 is reached.

[0077] It should be noted that in this embodiment, by installing the starting base, starting guide rail, main jacking cylinder and cylinder frame, backrest, jacking iron and other supporting facilities in the corresponding working well of the pre-treated hole 3, and after checking that they meet the requirements, the micro pipe jacking machine is hoisted onto the starting guide rail, thereby completing the installation and commissioning of the micro pipe jacking machine.

[0078] It should be noted that the working shaft can be a rectangular pipe jacking launching shaft or a rectangular pipe jacking receiving shaft, such as... Figure 7 As shown, the shaded area is the inner lining wall 8 of the working well.

[0079] It should be noted that you should refer to [link / reference]. Figure 7 and Figure 8Following the micro-jacking construction process, in the rectangular receiving opening 14, the micro-jacking machine 110 is gradually advanced into the pre-treatment hole 3. While jacking, it cuts and breaks the rock, and simultaneously discharges slag through mud-water circulation until the designed length of the treatment hole is reached. During the process, steel pipe sections are installed in a timely manner, and slurry pipes are installed inside the pipe sections and connected to the reserved grouting holes inside the micro-jacking machine. Simultaneously, surface settlement and deformation are monitored in real time, and feedback is provided promptly to adjust the jacking parameters of the micro-jacking machine. The longitudinal connections between steel pipe sections must ensure sufficient tensile strength. The micro-jacking construction is carried out according to the operational steps in the micro-jacking construction special plan. Figure 7 As shown, the steel ring on both sides of the tunnel entrance of the large pipe jacking machine has an inner contour 12 and an outer contour 11, which facilitates the installation and fixing of the water-stopping device used in the construction of large-section rectangular pipe jacking and ensures the stability and water-stopping effect of the water-stopping device, ultimately ensuring the safety of the construction of large-section rectangular pipe jacking.

[0080] Step S102: Sludge retraction.

[0081] The mud retraction includes at least steps S204-S207:

[0082] S204: Preparation of composite thick mortar 35.

[0083] It should be noted that composite concentrated mortar 35 has the characteristics of high concentration, low strength, good plastic fluidity, low permeability, and good stability. Preferably, composite concentrated mortar 35 is a slurry prepared by mixing bentonite, water, cement, and polymer additives in a certain proportion.

[0084] Furthermore, the composite concentrated mortar 35, possessing a certain strength, can compress and fill formation voids to prevent formation loss, playing a crucial role in the mud retraction process. The composite concentrated mortar 35 should not be too strong, exhibiting low strength, allowing for slight solidification within a short time. This allows it to support the weight of the superstructure while also accommodating the cutting action of the rectangular pipe jacking machine's cutterhead. Furthermore, the composite concentrated mortar 35 exhibits good plasticity and fluidity. Since the mud is pumped from the surface to the wellbore and then into the treatment hole, the corresponding concentrated mud must possess a certain degree of plasticity and self-flowability to be easily injected into the designed position of the pretreatment hole 3. Even further, when the composite concentrated mortar 35 is injected into the pretreatment hole in front of the micro-pipe jacking machine head, it generates a certain pressure to facilitate the retraction of the micro-pipe jacking machine and steel pipe sections under the action of the pullback device. In addition, the composite concentrated mortar 35 should also have low permeability, meaning it has a certain degree of water-stopping and is not prone to segregation or loss. This facilitates waterproofing of the pipe sections during pipe jacking while also preventing it from seeping into the formation. Furthermore, the composite thick mortar 35 plays a lubricating and drag-reducing role during pipe jacking. Due to its good stability, it can form a stable lubricating mortar sleeve, allowing the pipe jacking machine and pipe sections to move forward in the mortar sleeve and effectively isolate them from the soil, thereby significantly reducing the frictional resistance during jacking or retraction.

[0085] S205: Inject composite thick mortar 35 into the front of the micro jacking machine in the pre-treatment hole 3 to squeeze and fill the voids in the formation.

[0086] It should be noted that, in order to effectively squeeze and fill the voids in the strata, avoid strata loss, and control surface subsidence, the amount of mud used for compaction is taken as 1.5 to 2 times the theoretically calculated excavation volume of the micro-pipe jacking machine. The amount of mud used for compaction (A) per linear meter of 35% composite thick mortar is... i1 =kπD 2 / 4, the total sludge removal amount of a single pretreatment hole 3 is V i =A i1 (L i -L jg -L wh -L dq Where D is the excavation diameter of the micro pipe jacking machine, and L is the diameter of the pipe jacking machine. i For the design length of pre-treated hole 3, L jg L is the length of the reinforced area of ​​the tunnel entrance. wh For the thickness of the enclosure structure, L dq Where is the thickness of the plain concrete opening wall, and k is a coefficient, ranging from 1.5 to 2.

[0087] It should be noted that the amount of composite thick mortar 35 injected into a single pre-treated hole should be equal to or greater than the amount of cavity generated by the pullback, so as to form an overpressure sealed environment. This is beneficial for supporting and squeezing the surrounding strata through the overpressure reaction force to avoid strata loss, and also for the steel pipe section and the micro pipe jacking machine to retract under the action of the pullback device.

[0088] S206: The reaction force generated by the injection of composite thick mortar 35 creates an overpressure sealed environment in front of the micro jacking machine head in the hole, and then the steel pipe section is pulled back along with the micro jacking machine using a pullback device.

[0089] As a preferred embodiment, the preparation of composite thick mortar 35 involves: injecting composite thick mortar 35 into the front of the micro-jacking machine in the pre-treated hole 3 to compress and fill the formation voids; the reaction force generated by the injection of composite thick mortar 35 creates an overpressure sealed environment in front of the micro-jacking machine head in the hole; and using a pullback device to pull back the steel pipe along with the micro-jacking machine, so that the mortar injection reaction force and the pullback force jointly resist the frictional resistance generated when the steel pipe and the micro-jacking machine retract. The mortar injection and pullback steps are synchronized; the process continues until the pre-treated hole is completely filled with composite thick mortar 35 and the micro-jacking machine is completely withdrawn and the hole is sealed, thus completing the rock treatment of the current pre-treated hole. Specifically:

[0090] After the micro-jacking machine advances the current pre-treatment hole 3 to a preset length, composite thick mortar 35 is prepared and injected into the front of the micro-jacking machine's breast plate in the current pre-treatment hole through the grouting holes reserved on the cutterhead to squeeze and fill the formation voids. During the injection of composite thick mortar 35, the reaction force generated by the injection of composite thick mortar 35 creates an overpressure sealed environment in front of the machine head in the hole. The steel pipe section, along with the micro-jacking machine, can then be easily pulled back using a pullback device. This allows the mortar injection reaction force and the pullback force to jointly resist the frictional resistance generated when the steel pipe and the micro-jacking machine retract. The mortar injection and pullback steps are synchronized. The mortar injection and pullback steps are repeated cyclically until the entire space of the current pre-treatment hole is squeezed and filled with composite thick mortar 35.

[0091] It should be noted that during the injection of composite thick mortar 35, the mortar reaction force and the pull-back force work together to resist the frictional resistance generated when the steel pipe and the micro-jacking machine retract. The injected composite thick mortar 35 can generate a certain reaction force to squeeze and fill the voids in the ground in front of the micro-jacking machine and form overpressure to support the upper soil and prevent ground loss. At the same time, the overpressure sealed environment generates a reaction force for the micro-jacking machine head, which is conducive to the retraction of the micro-jacking machine and the steel pipe section under the action of the pull-back device. Finally, all the space of the current pre-treated hole 3 is squeezed and filled by composite thick mortar 35, avoiding ground subsidence caused by ground loss.

[0092] It should be noted that, in this embodiment, the sum of the reaction force generated by the injection of composite thick mortar 35 and the pulling force generated by the pullback device must be greater than or equal to the frictional resistance generated during the retraction. For example, if the frictional resistance of a steel pipe section in a pre-treated hole and the retraction of a micro jacking machine is calculated to be 5000 kN and the pulling force that the pullback device can provide is 2500 kN, then the reaction force generated when injecting composite thick mortar 35 must be greater than or equal to 2500 kN.

[0093] Furthermore, surface settlement and deformation are monitored in real time during mud retraction, thereby adjusting the mud pressure, retraction force, and retraction speed accordingly. The injection of concentrated mud and the retraction of the pipe jacking machine must be performed simultaneously. The injection volume and the cavity volume generated by the retraction must be kept consistent, even with over-pressure and over-volume injection. The reaction force generated by over-pressure injection of concentrated mud facilitates the retraction of the micro-pipe jacking machine and steel pipe sections under the action of the retraction device. Retraction before injection is strictly prohibited.

[0094] In this embodiment, after the micro jacking machine advances to the designed length of the treatment hole, composite thick mortar 35 is injected into the front of the breast plate of the micro jacking machine through the grouting hole. First, a certain amount of composite thick mortar 35 is injected to squeeze and fill the gap between the cutter head of the micro jacking machine and the formation. Then, while injecting composite thick mortar 35, the steel pipe section and the micro jacking machine are gradually pulled back in the working well using a jacking device.

[0095] Furthermore, during the injection of composite thick mortar 35 and the pullback of the steel pipe section along with the micro jacking machine, injection and pullback must be carried out simultaneously. The reaction force generated by the injection of composite thick mortar 35 creates an overpressure sealed environment in front of the micro jacking machine head within the borehole. The pullback device can then easily pull back the steel pipe section along with the micro jacking machine, with mortar injection and pullback occurring synchronously. The injection volume and the cavity volume generated by pullback must be kept consistent, even with overpressure and over-injection. Pulling before injection is strictly prohibited. If an overpressure environment is not created in front of the micro jacking machine head to generate sufficient reaction force, the pullback device in the working shaft will need to provide a large pulling force. This can easily cause the pullback device to break or the micro jacking machine to become detached from the steel pipe section. In severe cases, this can lead to soil loss around the steel pipe section and the overlying soil, resulting in ground settlement and deformation.

[0096] It should be noted that when pulling back the steel pipe section along with the miniature pipe jacking machine, a pullback connector is welded onto the steel pipe section inside the well, and the connector is effectively connected to the pullback jacking equipment. The beginning and end of each steel pipe section are welded together, and the front end of the first steel pipe section is welded to the rear end of the miniature pipe jacking machine.

[0097] In this embodiment, please refer to Figure 9 and Figure 10 This is a schematic diagram of the retraction of a miniature pipe jacking machine. The pre-treatment pipe jacking starting shaft and the large-section rectangular pipe jacking receiving shaft are the same working shaft. During the jacking process, the large-section rectangular pipe jacking machine 91 encounters bedrock and large-diameter boulders 9 in the lower part of its cross-section. The cutterhead of the large-section rectangular pipe jacking machine 91 cannot cut and excavate the bedrock and boulders 9, so a miniature pipe jacking machine 110 is used to break up the bedrock and boulders 9. The miniature pipe jacking machine 110 jacks, installs pipes, breaks up rocks, and removes slag in the pre-treatment hole until it reaches the designed length of the current pre-treatment hole. Then, composite thick mortar 35 is injected. Under the combined action of the reaction force generated by the mortar injection and the pulling force generated by the pullback device, the steel pipe section along with the miniature pipe jacking machine is retracted. The multiple steel pipe sections 100, which are connected end to end, are retracted into the working shaft and recovered. Once all the pre-treatment holes have been constructed, the bedrock and boulders within the excavation range of the large-section rectangular pipe jacking machine 91 will be completely replaced and filled with composite thick mortar. The replaced strata can adapt to the cutting and excavation of the large-section rectangular pipe jacking machine 91. After that, the large-section rectangular pipe jacking machine 91 can advance and construct according to the designed side line 93 (or the designed range of the top of the large pipe jacking section and the side line 93) until the tunnel 92 is completed.

[0098] S207: Until the pre-treatment hole 3 is completely filled by the composite thick mortar 35 and the micro pipe jacking machine is completely withdrawn and sealed, the bedrock and boulder treatment of the current pre-treatment hole 3 is completed.

[0099] As a preferred embodiment, when the micro pipe jacking machine is gradually squeezed by the composite thick mortar 35 and retracted to the opening of the current pre-treatment hole 3 under the action of the pullback device and is fully received, the opening of the current pre-treatment hole 3 is sealed with bricks or steel plates.

[0100] In this embodiment, please refer to Figure 11 When the miniature pipe jacking machine retracts to the plain concrete opening wall, the injection of composite thick mortar 35 is stopped. Then, the miniature pipe jacking machine is quickly retracted into the working shaft, thus completing the pre-treatment area 111. Simultaneously, it is observed whether the injection volume of composite thick mortar 35 is sufficient and requires strong overall self-stability, i.e., as... Figure 12 The opening of the miniature pipe jacking machine is sealed by 34. After sealing the opening with bricks or steel plates, the water-stopping device 33 of the treatment hole can be removed, which facilitates the construction of the opening structure of the next pre-treatment hole.

[0101] Furthermore, during the jacking process, the micro pipe jacking machine may damage the water-stop steel ring and inner lining wall at the reserved opening of the large-section rectangular pipe jacking working shaft. Therefore, it is necessary to carry out local repairs on the water-stop steel ring and inner lining wall of the large pipe jacking to ensure the safety of the starting and jacking of the large-section rectangular pipe jacking.

[0102] As a preferred embodiment, after completing the rock breaking process of the current pre-treatment hole 3, the method further includes:

[0103] The remaining pre-treated holes 3 were then subjected to micro-jacking rock crushing and mud compaction retreat.

[0104] In this embodiment, pretreatment of the bedrock and boulders in all pretreatment holes 3 was achieved. A miniature pipe jacking machine was used to cut and break up the rock within the remaining pretreatment hole 3 area, jacking the pipe to the designed length of each pretreatment hole 3. While injecting composite thick mortar 35 to fill the formation voids, the steel pipe section, along with the miniature pipe jacking machine, was pulled back out of the hole by overcoming the retraction friction under the combined action of the reaction force generated by the injected composite thick mortar 35 and the pulling force generated by the pullback device. Then, the hole opening was sealed. The total amount of composite thick mortar 35 used for slurry filling is V1 = ΣV i1 .

[0105] As a preferred embodiment, after micro-jacking rock breaking and mud removal are performed on all pre-treated holes 3, the rock formation is replaced with a treated formation that can adapt to the cutting and excavation of a rectangular pipe jacking machine, specifically including:

[0106] The construction equipment in the pre-treatment hole 3 is removed and the damaged structure in the working well is repaired. A water-stopping device 33 for rectangular pipe jacking is installed at the reserved portal in the area to be excavated by the large-section rectangular pipe jacking machine. The large-section rectangular pipe jacking machine is installed and debugged so that it can smoothly jack up the tunnel in the area to be excavated and the treated strata until the tunnel is completed.

[0107] It should be noted that you should refer to [link / reference]. Figure 13 The pre-treatment hole 3 construction facilities and site were cleared, including repairing the wear on the pre-embedded waterstop steel plate of the large-section rectangular jacking tunnel portal caused by the bedrock and boulder pre-treatment construction, and removing the temporary steel supports. The inner retaining structure of the large-section rectangular jacking tunnel portal and the plain concrete portal wall constructed during the pre-treatment construction were chiseled away, and rubber curtains and other large-section rectangular jacking machine waterstop devices 13 were installed on the waterstop steel plate of the large-section rectangular jacking tunnel portal. The large-section rectangular jacking tunnel was excavated according to the rectangular jacking construction process until the tunnel was completely completed.

[0108] Specifically, based on the distribution of bedrock and boulders, some cutterheads of large-section rectangular jacking pipes are equipped with high-strength alloy cutters with high wear resistance.

[0109] The micro pipe jacking machine in this embodiment of the invention has the characteristics of being able to efficiently break bedrock or boulders with high rock strength, with no limit on the jacking construction length, large coverage area, less prone to borehole deviation, controllable posture, and guaranteed construction accuracy; it adopts the green, safe, environmentally friendly, and efficient slurry balance pipe jacking method, which causes little disturbance to the strata, controllable ground settlement, and minimal impact on the surrounding environment; the process is simple and the construction speed is fast.

[0110] Simultaneously, composite thick mortar is used to fill the strata treated by the micro-jacking machine. This involves simultaneously injecting the composite thick mortar and pulling back the steel pipe section along with the micro-jacking machine under the action of the pullback device. This reduces stratum disturbance and avoids stratum loss, making ground settlement controllable. The bedrock and boulder pretreatment technology provided in this embodiment effectively replaces the rock strata with a low-strength treated stratum suitable for rectangular pipe jacking machine cutting and excavation. The overall construction pretreatment covers a wider area, requires fewer pretreatment operations, effectively reduces stratum disturbance, and ensures controllable ground settlement. This guarantees that during subsequent large-section rectangular pipe jacking construction in soft-over-hard strata with bedrock or boulder, the jacking posture is controllable and less prone to deflection. The cutterhead experiences relatively uniform stress, reducing cutterhead excavation torque, ensuring smooth auger removal, and a smooth and safe jacking process.

[0111] Implementing the above embodiments has the following effects:

[0112] The technical solution of this invention combines micro-jacking rock breaking and mud-pressing retreat. The micro-jacking construction is fast and efficient in breaking bedrock or boulders within the excavation range of a large-section rectangular jacking pipe, and reduces the strength and size of the rock. Then, mud-pressing retreat is carried out, that is, composite thick mortar is injected in front of the micro-jacking machine in the pre-treated hole to squeeze and fill the voids in the strata. At the same time, the reaction force generated by the injection of composite thick mortar creates an overpressure sealed environment in front of the micro-jacking machine head in the hole. Then, the steel pipe and the micro-jacking machine are pulled back using a pullback device. The mud-pressing reaction force and the pullback force jointly resist the frictional resistance generated when the steel pipe section and the micro-jacking machine are pulled back. The mud pressing and pullback are synchronized. In the cavity created by the pullback, the same or even a larger volume of composite mortar is injected. The reaction force generated by the injected composite mortar facilitates the retraction of the micro-jacking machine and steel pipe sections under the action of the pullback device. The mortar injection and pullback are repeated until the pre-treated hole is completely filled with composite mortar and the micro-jacking machine is completely withdrawn and the hole is sealed. By combining the above two technologies, the rock strata are effectively replaced with low-strength treated strata that can adapt to the cutting and excavation of rectangular pipe jacking machines. This method has no limitation on the length of the pre-treatment, a larger coverage area, and fewer pre-treatment operations, effectively reducing disturbance to the strata, controlling ground settlement, and ensuring that the jacking posture is controllable and less prone to deflection in the soft upper and hard lower strata with bedrock or boulders during subsequent large-section rectangular pipe jacking construction. The force on the cutterhead is relatively uniform, reducing the cutterhead excavation torque, ensuring smooth auger excavation, and making the jacking project smooth and safe.

[0113] Furthermore, the technical solution of the present invention has strong adaptability to different strata such as bedrock or boulders, large pretreatment coverage area, simple construction process, fast construction speed, cost saving, small disturbance to the strata during construction, controllable and safer construction settlement, and the use of a micro pipe jacking machine to crush the rock in the pretreatment hole makes the construction process efficient and safe. Compared with the prior art, it is not necessary to expand the diameter of the rectangular pipe jacking machine cutter head after the horizontal anchor bolt pretreatment, so the economic benefits of the present invention are obvious.

[0114] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for pretreatment of bedrock and boulders for large-section rectangular pipe jacking, comprising a large-section rectangular pipe jacking machine and a micro pipe jacking machine, wherein the two ends of the travel path of the large-section rectangular pipe jacking machine have a launching shaft and a receiving shaft, and a rectangular pipe jacking tunnel portal enclosure structure is respectively provided in the launching shaft and the receiving shaft; The feature is that, before the operation of the large-section rectangular pipe jacking machine, the bedrock and boulders in the travel path are pre-treated using the miniature pipe jacking machine. Includes the following steps: 1) Break up the bedrock and boulders along the route; 1.1) Horizontal geological exploration boreholes are drilled from the starting well and / or receiving well to determine the distribution range and strength of bedrock or boulders, and to check the soil reinforcement effect and water leakage in the portal reinforcement area of ​​the large-section rectangular pipe jacking machine's to-be-excavated range. 1.2) Construct pre-treated orifice walls from the launching well and / or receiving well; Based on the distribution of bedrock and boulders detected in step 1.1), and in conjunction with the arrangement of the cutterhead of the large-section rectangular pipe jacking machine and the cutterhead cutting blind zone, the layout scheme of the pretreatment holes is determined within the working portal ring of the launching shaft and / or receiving shaft. Specifically, at the location of the opening, the pre-treatment holes are arranged reasonably from bottom to top, and the position, spacing and number of the pre-treatment holes are determined. Based on the layout range of each pretreatment hole, the size of the opening of each pretreatment hole is determined. A concrete retaining wall is constructed inside the water-stop steel ring of the large-section rectangular pipe jacking machine tunnel entrance and closely attached to the working well enclosure structure as the opening structure of the pretreatment hole, i.e., the pretreatment hole opening wall, as the opening structure of the pretreatment hole. 1.3) Install a water-stopping device; The concrete retaining wall and enclosure structure within the pre-treated hole opening area are cut using a water drill, and the water-stopping device for the micro pipe jacking machine is installed at the opening of the pre-treated hole. 1.4) The miniature pipe jacking machine jacks in, loads steel pipe sections, crushes rocks, and removes slag until the preset length has been reached; 2) Sludge retraction, The process includes: preparing composite thick mortar; injecting composite thick mortar into the front of the micro jacking machine in the pre-treated hole to squeeze and fill the formation voids; using the reaction force generated by the injection of composite thick mortar to create an overpressure sealed environment in front of the micro jacking machine head in the hole; using a pullback device to pull back the steel pipe along with the micro jacking machine so that the mortar injection reaction force and the pullback force together resist the frictional resistance generated when the steel pipe and the micro jacking machine retract. The mortar injection and pullback steps are synchronized; until the pre-treated hole is completely filled with composite thick mortar and the micro jacking machine is completely withdrawn and the hole is sealed. 3) Complete the treatment of bedrock and boulders in the travel path.

2. The method for pretreatment of bedrock and boulders for large-section rectangular pipe jacking according to claim 1, characterized in that, The height of the concrete retaining wall should exceed the top of the pre-treated hole by 20cm to 30cm; in addition, several temporary steel supports need to be installed above the concrete retaining wall to support the water-stop steel rings embedded within the opening of the large-section rectangular jacking pipe.

3. The method for pretreatment of bedrock and boulders for large-section rectangular pipe jacking according to claim 1, characterized in that, The concrete retaining wall is connected to the retaining structure piles of the launching well and / or receiving well by steel bars. The steel bars are arranged circumferentially along the concrete retaining wall and must be arranged outside the range of the pre-treated hole.

Images