A pipe jacking construction method for complex strata with sudden changes in strata

Abstract

A method for pipe jacking construction in a complex stratum with sudden changes in strata, comprising the following construction steps: constructing a pipe shed at the top outer contour of the excavation cross section to achieve support at the top of the excavation cross section; dividing the excavation cross section into a rock stratum area and a soft soil area, arranging positioning drilling holes in the rock stratum area, and positioning grouting reinforcement holes in the soft soil area; drilling horizontally in the rock stratum area according to the positioning points of the drilling holes, and after the drilling of the drilling holes is completed, injecting bentonite slaked lime mixed slurry into the drilling holes to fill the drilling holes; constructing horizontal high-pressure rotary jet piles at each grouting reinforcement hole in the soft soil area to achieve reinforcement of the strata in the soft soil area; after the strata in the soft soil area and the rock stratum area are processed, excavation is carried out along the excavation route using a pipe jacking machine. The present application can achieve smooth excavation construction in complex strata with sudden changes in strata.

Description

Technical Field

[0001] The present application belongs to the technical field of pipe jacking construction, and in particular, relates to a pipe jacking construction method in complex strata with sudden changes in strata. Background Art

[0002] The pipe jacking method is a trenchless pipeline laying technology for underground projects similar to the shield method. It uses a pipe jacking machine to drill holes and push prefabricated pipes into the jacking working shaft to form a continuous lining structure.

[0003] With the development of construction equipment manufacturing in my country, underground pedestrian crossings attached to subway stations have widely adopted rectangular pipe jacking construction, which reduces ground excavation and thus reduces the impact of subway construction on surrounding road traffic and underground pipelines.

[0004] During the jacking construction process, the stratum conditions have a great impact on the smooth advancement of the jacking. At present, there are geological conditions with sudden changes in the strata. Due to the sudden changes in the strata, the stratum structure is complex, the stratification is not obvious, and other strata are mixed in the strata, resulting in difficulties in jacking. Especially when encountering large-diameter boulders, cemented gravel layers and other high-strength rock strata, the rock breaking capacity of conventional pipe jacking machines does not exceed 5MPa. It is difficult for pipe jacking machines to advance in such strata, the posture is difficult to control, the ground settlement is uncontrollable, and the boulders are difficult to unearth after entering the soil bin, and large boulders are easily stuck in the spiral machine disk. Summary of the invention

[0005] The present application provides a pipe jacking construction method for complex strata with sudden changes in strata, which is used to solve the problem that it is difficult to excavate in hard rock strata during rectangular pipe jacking construction.

[0006] The present application provides a method for pipe jacking construction in complex strata with sudden changes in strata, including the following construction steps:

[0007] A pipe shed is constructed on the top outer contour of the excavation cross section to support the top of the excavation cross section;

[0008] Divide the excavation cross section into rock layer area and soft soil area, arrange positioning drilling holes in the rock layer area, and locate grouting reinforcement holes in the soft soil area to achieve the replacement of rock layer strata;

[0009] Horizontal drilling is performed in the rock formation area according to the positioning point of the drilling hole. After the drilling of the drilling hole is completed, a mixed slurry of bentonite and slaked lime is injected into the drilling hole to fill the drilling hole;

[0010] Carry out horizontal high-pressure jet grouting pile construction at each grouting reinforcement hole in the soft soil area to reinforce the strata in the soft soil area;

[0011] After the ground treatment in the soft soil and rock areas is completed, the excavation is carried out along the excavation route using a pipe jacking machine.

[0012] Furthermore, the drilling and grouting of the boreholes, as well as the construction of horizontal high-pressure jet jet piles from the grouting reinforcement holes into the stratum can be carried out according to the principle of approaching from both ends of the excavation route to the middle.

[0013] Furthermore, when drilling a borehole, if a formation change is encountered, drilling should be stopped, and grouting should be injected at the end of the borehole to seal the end of the borehole.

[0014] Furthermore, during the drilling process, if the water output of a single hole is less than 30L / min, drilling can continue; if the water output of a single hole is greater than 30L / min, drilling should be stopped immediately and grouting should be carried out to seal the hole.

[0015] Furthermore, the arrangement spacing of the drilling holes at the outer edge of the rock formation area is denser than that in the middle area of ​​the rock formation area.

[0016] Furthermore, after the drilling of the boreholes is completed, all the boreholes are pressure tested with clean water. After the pressure test is completed, the grouting is slowly pressurized. After the grouting is completed, the pressure is re-pressurized until the slurry is fully diffused and penetrated, and then the hole sealing operation is performed.

[0017] Furthermore, the drilling area of ​​the drill hole covers the interface between the rock layer area and the soft soil area.

[0018] Furthermore, before the soil layer transformation construction in the rock layer area and the soft soil area is carried out, a construction step is included in which settlement monitoring points are arranged on the ground above the excavation route, and the settlement monitoring points are densely arranged at the pipeline.

[0019] Furthermore, when using the pipe jacking machine to advance forward, the pipe jacking machine adopts a composite cutter disc, which is a composite cutter disc composed of a tearing knife, a shell knife and a fishtail knife.

[0020] Furthermore, the composite cutter disc is configured as a 6-spoke type, a reinforcement ring is provided on the outer edge and the middle of the spoke, tearing knives are provided on both sides of the spoke, heavy tearing knives are provided at the ends, a shell knife made of large alloy is provided in the middle, a fishtail knife is provided in the middle of the cutter disc, and the shell of the pipe jacking machine is provided with a scraper with wear-resistant welding.

[0021] In summary, the present application includes at least one of the following beneficial effects:

[0022] 1. Before the rectangular pipe jacking construction, the construction method of the present application first pre-treats the hard rock layer, that is, drills holes in the hard rock layer and refills the holes with slurry to reduce the structural strength of the rock layer area at the excavation face; on the other hand, the silty clay layer is reinforced by grouting to increase the soil strength in the soft soil area, thereby balancing the jacking resistance of each area during the jacking process of the rectangular pipe jacking machine, so that the jacking construction in complex strata with sudden changes in the strata can be smoother.

[0023] 2. The construction method of the present application simultaneously approaches the drilling hole in both directions of the starting tunnel portal and the receiving tunnel portal, which can reduce the drilling depth of the single-sided drilling hole, thereby reducing the construction difficulty and improving the drilling efficiency of the drilling hole; at the same time, grouting reinforcement is performed on the soft soil stratum in both directions, which can shorten the grouting interval, improve the construction efficiency, and can adjust the grouting construction in real time according to the stratum conditions.

[0024] 3. According to the geological conditions after stratum treatment, the cutter disc structure is adaptively adjusted. Through the combination of multiple cutter discs, the cutting kinetic energy of the pipe jacking equipment can be enhanced, thereby achieving smoother excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a stratigraphic diagram of a certain excavation section of the stratum excavated in this application;

[0026] Figure 2 It is a schematic diagram of the excavation section after the ground treatment is completed in this application;

[0027] Figure 3 This is a schematic diagram of the stratigraphic cross section used in this application to show the pipe jacking route;

[0028] Figure 4 It is a schematic diagram of the structure of the rectangular composite cutter disc of the present application;

[0029] Figure 5 yes Figure 4 Schematic diagram of the middle MM section;

[0030] Figure 6 yes Figure 4 Schematic cross-section of NN.

[0031] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0032] 1. Pipe shed; 2. Rock layer area; 3. Soft soil area; 4. Drilling hole; 5. Grouting reinforcement hole. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-6 This application is described in further detail.

[0034] The present application embodiment discloses a method for pipe jacking construction in complex strata with sudden changes in strata, which is aimed at the geological situation where cemented conglomerate suddenly changes into a silty clay layer, and some sections of the excavation route also include a gravel layer, such as Figure 1 As described above, on the jacking cross section, cemented gravel and silty clay layers coexist, so that during the jacking process, when the jacking pipe is jacked in the cemented gravel layer, the resistance is large and the jacking is difficult; while in the silty clay layer, the jacking is smooth, which causes inconsistent forward resistance on both sides of the jacking machine, making jacking difficult.

[0035] A method for pipe jacking in complex strata with sudden changes in strata includes the following construction steps: Figure 2 and Figure 3 :

[0036] Step 1: construct a pipe shed 1 on the top outer contour of the excavation route. The pipe shed 1 is used to support the top of the excavation route and reduce the occurrence of earth collapse or surface subsidence during the jacking process.

[0037] Due to the shallow soil cover of the structure during pipe jacking construction in the urban area, and the proximity to the existing municipal pipelines, the municipal pipelines are prone to settlement and even damage accidents during pipe jacking construction. To protect the safety of the pipelines, when the pipelines are located within 1.5 meters outside the structural outline, a Φ159@300 pipe shed 1 is used between the pipelines and the structure for protection to reduce the disturbance to the pipelines during pipe jacking construction. At the same time, the design of the pipe shed 1 can also support the smooth progress of the pipe jacking construction to reduce the collapse of the soil covering the top, which may cause the interruption of the pipe jacking construction.

[0038] When designing pipe shed 1, the steel pipe is hot-rolled seamless steel pipe Φ159, with a wall thickness of 8mm and a section length of 3m. The horizontal and vertical spacing of the steel pipe is 300mm. The design length of pipe shed 1 is determined according to the position of the pipeline and the tunnel portal, and the end of pipe shed 1 exceeds the pipeline by no less than 2m. The steel pipe is driven into the formation at an elevation angle of 1° and is driven into the formation parallel to the center line of the channel. Cement slurry is used for grouting, and the water-cement ratio of cement slurry is 1:1. The grouting of pipe shed 1 is mainly filling type, and the grouting pressure is strictly controlled.

[0039] Due to the sudden change of strata, the geological conditions of each drilling cross section on the drilling route are different. For areas with cemented conglomerate sudden change strata at the edge of the excavation area, the top support can be achieved directly through the cemented conglomerate. However, the drilling cross section of some sections may not include cemented conglomerate sudden change strata. By designing the pipe shed 1, the top support of the entire excavation section can be achieved, making the entire construction process cycle safer.

[0040] The construction operation of pipe shed 1 specifically includes the following processes: setting up drilling platform, installing drilling rig, drilling, hole cleaning, hole inspection, installing steel pipe of pipe shed 1, grouting, and dismantling the platform.

[0041] In the drilling process, in order to facilitate the installation of steel pipes, the drill bit diameter is Φ200mm. In order to facilitate the insertion of pipes, the drilling depth should be greater than the designed 0.5m. The drilling sequence is from high-position holes to low-position holes. The first section of the drill rod is drilled into the soil layer. When there is 20 to 30cm left at the tail, the drilling is stopped. The drill rod is clamped manually with two pipe clamps, and the drill rig is reversed at low speed to disengage the drill rod. The drill rig returns to its original position along the guide rail, and the second drill rod is manually loaded, and the connecting sleeve is installed at the front end of the drill rod. The drill rig is sent to the tail of the first drill rod at low speed, and the directions are aligned and connected into one. After the drill rod is drilled to the required depth, the drill rod is disassembled in the same way.

[0042] During the hole cleaning and hole testing process, the drill bit is used to sweep the hole back and forth to remove floating debris to the bottom of the hole, ensuring that the hole diameter and hole depth meet the requirements and prevent hole blockage; then high-pressure gas is used to clean the drill debris from the bottom of the hole to the hole mouth; finally, the drill rod is used to detect the hole depth, and the total station is used to detect the inclination.

[0043] In the process of installing the steel pipe of pipe shed 1, Φ6-8mm grouting holes are drilled around the steel pipe, a special guide drill is welded at the front end, and a Φ6-8mm overflow hole is drilled in the middle of the large pipe shed 1. The overflow holes are arranged in a plum blossom shape to prevent dead corners in grouting. The spacing of the overflow holes is 200mm, and no holes are drilled within 150cm of the tail of the steel pipe to prevent leakage. The steel pipe joints are connected by threaded connections, and the thread length is 150mm.

[0044] After the steel pipes of pipe rack 1 are installed, cement single-liquid slurry is used with a water-cement ratio of 1:1 and the grouting pressure is controlled between 0.5 and 1.0 MPa.

[0045] Step 2: Set up settlement monitoring points on the ground above the excavation route. Before the subsequent drilling operation, settlement monitoring points need to be set up to monitor surface settlement, underground pipeline settlement, surrounding road settlement, and building settlement during the pipe jacking construction process. Specifically, the monitoring method adopts a precise leveling method, using an electronic level to obtain the initial elevation at the settlement detection point and the nearby benchmark point, and monitor the ground settlement changes at the settlement detection point during the entire construction cycle.

[0046] Among them, the arrangement principle of the settlement detection points is: the settlement detection points are arranged according to the monitoring design drawings, one settlement detection point is arranged along the cross section of the interval at a distance of 3.5m, one settlement detection point is arranged along the longitudinal section at a distance of 5m, and the settlement detection points are arranged densely in the pipeline. The construction method of the settlement detection point includes the following steps: using a water drill or a car drill to drill an observation hole downward on the surface without obstacles underground, and taking an observation hole with a diameter of 22cm as an example; driving a detection rod into the observation hole, the diameter of the detection rod is smaller than the diameter of the observation hole. In the embodiment of the present application, it can be a threaded steel bar with a diameter of 18cm, the length of the threaded steel bar is 0.8m~1.2m, and the top is ground and welded with a stainless steel oval head; after the detection rod is driven into the ground, fine sand is filled around the detection rod and compacted. In one of the embodiments, if the surface is concrete or asphalt concrete pavement, the bottom of the detection rod should at least enter the roadbed under the pavement by 20cm and be isolated from the pavement.

[0047] In order to reduce the impact of road settlement on the settlement monitoring data of the settlement detection point, the detection rod shall not be fixed in the observation hole with concrete or cement. Finally, the top of the settlement observation point is covered with an ABS engineering plastic protective cover for protection. All settlement detection points are marked with red paint and uniformly numbered to facilitate construction workers to find and monitor.

[0048] Step 3: Drilling holes 4 are arranged and drilled at intervals in the cemented conglomerate area of ​​the excavation face, and grouting reinforcement holes 5 are located at intervals in the silty clay layer area of ​​the excavation face.

[0049] For the convenience of description, the cemented gravel layer area of ​​the excavation face is referred to as the rock layer area 2, and the silty clay layer area is referred to as the soft soil area 3. It should be noted that as the excavation route advances, the area occupied by the rock layer area 2 and the soft soil area 3 on each excavation section is dynamically changing, and the excavation section of some sections is also mixed with gravel layers. When arranging the drilling holes 4, the density of arranging the drilling holes 4 on the side of the excavation section is greater than the arrangement density of the drilling holes 4 in the middle area of ​​the excavation end face, thereby forming a relatively connected drilling area on the side of the excavation section, so that the jacking drill is not easy to deviate, lift up or get stuck during the drilling process in the later stage.

[0050] During the specific construction, first, at both ends of the route to be excavated, excavation is carried out downward from the surface to form a starting tunnel portal and a receiving tunnel portal. The construction personnel determine the drilling points of the drilling hole 4 and the grouting reinforcement hole 5 at the stratigraphic sections at the starting tunnel portal and the receiving tunnel portal, based on the geological survey report and the actual rock distribution during the excavation of the station and the auxiliary foundation pit.

[0051] The ground treatment of rock layer area 2 and soft soil area 3 can be carried out simultaneously to shorten the construction period. When constructing rock layer area 2, a horizontal drilling device is used to drill holes into the rock layer. The horizontal drilling device can be a screw machine. When constructing the soft soil layer, a grouting pipe is directly driven into the grouting reinforcement hole 5.

[0052] In a preferred embodiment, the drilling construction of the drilling hole 4 is carried out simultaneously from the end faces of the starting tunnel portal and the receiving tunnel portal, and the drilling of the drilling hole 4 is carried out according to the principle of approaching from both ends to the middle, so as to improve the construction efficiency and speed up the drilling progress. During the drilling process of the drilling hole 4, if the water output of a single hole is less than 30L / min, the drilling can continue; if the water output of a single hole is greater than 30L / min, the drilling should be stopped immediately and grouting should be performed to seal it.

[0053] In addition, during the drilling process of the borehole 4, if the stratum changes from the cemented conglomerate layer to the silty clay layer or to the crushed stone stratum, the drilling needs to be stopped immediately. Grouting treatment is performed on the end area of ​​the borehole 4 to reinforce the stratum at the end of the borehole 4, reduce the disturbance to the crushed stone stratum, or reinforce the silty clay layer.

[0054] Step 4: After the drilling of the borehole 4 is completed, the bentonite slaked lime mixed slurry is injected into the borehole 4 to fill the borehole 4. At the same time, a rotary jet hole is drilled at the location of the grouting reinforcement hole 5 in the soft soil area 3 by a horizontal drilling rotary jet machine, and high-pressure slurry is sprayed during the drilling process, and finally a horizontal high-pressure rotary jet pile is formed in the soft soil area 3 stratum to achieve reinforcement of the soft soil area 3 stratum.

[0055] When grouting the drilling hole 4, the grouting pipe and the pressure relief pipe are installed immediately after the drilling hole 4 is formed, and after effective plugging, the drilling hole 4 is filled with bentonite slaked lime mixed slurry. The grouting pipe can be a PVC pipe with a diameter of 50mm, and the pressure relief pipe can be a PVC elbow with a diameter of 25mm. The sealing of the grouting pipeline is checked by pressurizing water, and the rock cracks are flushed at the same time to expand the slurry passage and increase the density of the slurry plug.

[0056] Specifically, after the drilling is completed, all the drilled holes 4 are pressure tested with clean water. On the one hand, the holes are cleaned to increase the diffusion area of ​​the dual-liquid slurry; on the other hand, it is checked which drilled holes can be pressurized with clean water, and the holes that can be pressurized with clean water are marked.

[0057] During grouting, apply pressure slowly and evenly. Generally, when the pressure reaches the specified value of 1-1.5MPa, maintain the pressure until the overflow hole overflows with continuous and full cement slurry. Use a wooden plug to plug the overflow hole and maintain the pressure for more than 3-5 minutes to allow the slurry to fully diffuse and penetrate the bottom of the board to achieve the effect of compaction and filling. If pressure loss is found during the pressure holding process, it should be replenished in time. After the pressure holding time meets the requirements, open the unloading switch to slowly reduce the pressure and return the pressure to zero.

[0058] Re-pressurization: The re-pressurization should be completed within 0.5-2 hours. The pressure should be increased slowly and evenly. Generally, when the pressure reaches the specified value of 1.5-2MPa, the pressure should be maintained for more than 3-5 minutes to allow the slurry to fully diffuse and penetrate the bottom of the board to achieve the effect of compaction and filling. If the pressure is lost during the pressure holding process, it should be replenished in time. After the pressure holding time meets the requirements, open the unloading switch to slowly reduce the pressure and return the pressure to zero.

[0059] Sealing the hole: When the grouting is completed, the grouting plug should be pulled out immediately and a wooden plug should be inserted immediately to allow enough time for the double liquid slurry to fully solidify. After ensuring that the double liquid slurry will not be squeezed out of the hole, the wooden plug can be pulled out after 8-10 minutes and the hole should be permanently sealed with quick-setting cement mortar. When sealing the hole, it should be compacted with a chisel and then smoothed.

[0060] When constructing horizontal high-pressure jet grouting piles in soft soil area 3, a jet grouting hole is drilled horizontally or in an inclined direction in the loose and weak stratum using a horizontal drilling jet grouting machine, and a high-pressure grout of more than 20 MPa is sprayed from the small nozzles at the rear and side of the drill bit. The nozzle sprays from the bottom of the hole while rotating and retreating; the sprayed high-pressure grout and the soil and rocks cut and destroyed within a certain range quickly condense to form a columnar consolidation body, whose strength is significantly higher than that of the original stratum, so that the surrounding stratum is reinforced.

[0061] When reinforcing the soft soil zone 3, horizontal MJS piles can be used to achieve stratum reinforcement, and horizontal WSS grouting can also be used to achieve stratum reinforcement. However, the slurry of the WSS grouting method is mainly diffused in the stratum through the grouting pressure, and the diffusion range is uncertain. The controllability is not as high as that of horizontal MJS and horizontal rotary jet piles. Especially in locations with shallow overburden and large soft soil voids, when the grouting pressure is not properly controlled, the slurry is easy to diffuse into the rock zone 2, and the broken hard rock will be re-consolidated, resulting in a decrease in the pre-crushing construction effect of the rock zone 2. The construction cost of horizontal MJS piles is relatively high. Although the effect of horizontal high-pressure rotary jet piles is slightly inferior to that of horizontal MJS piles, the reinforced soil can meet the soft soil stratum reinforcement requirements on site.

[0062] Step 5: After the bentonite-lime mixed slurry in the drill hole 4 in the rock layer area 2 solidifies and the horizontal high-pressure rotary jet piles in the soft soil area 3 are formed, the pretreatment of the soil layer is completed, and then a tunneling surface with a small strength difference is formed along the tunneling end face. At this time, a pipe jacking machine is used to tunnel along the tunneling route from the starting face of the tunneling route.

[0063] During the drilling process, a rectangular composite cutter head is used for drilling. Figures 4 to 6 The cutterhead of the earth pressure balance pipe jacking machine is set to 6 spokes, with a reinforcement ring set on the outer edge and the middle of the spokes, tearing knives on both sides of the spokes, heavy tearing knives at the ends, and a shell knife made of large alloy in the middle. The shell knife is 37mm higher than the tearing knife. A fishtail knife is set in the middle of the cutterhead, and the fishtail knife is 260mm high to enhance the cutting ability of the cutterhead on the residual cemented conglomerate. The shell of the pipe jacking machine is set with a wear-resistant welded blade to ensure that the jacking section meets the design requirements. See the attached for the cutterhead configuration Figure 3 .

[0064] The design principle of the pipe jacking construction method for complex strata with sudden changes in strata in the present application is: for complex strata with sudden changes in strata, different strata areas with different hardness and softness will be formed in each excavation cross section during the excavation process, which will make it difficult for the pipe jacking machine to excavate smoothly. The construction method of the present application achieves stratum replacement by setting a drilling hole 4 in the rock stratum area 2 and injecting a mixed slurry of bentonite and slaked lime into the drilling hole 4 to reduce the hardness of the rock stratum area 2; at the same time, horizontal high-pressure rotary jet piles are used for grouting in the soft soil area 3 to enhance the hardness of the soil layer in the soft soil area 3, thereby making the hardness of each area of ​​the excavation surface of the pipe jacking machine more balanced, and with the design of the cutterhead structure, the smooth excavation of the entire line of the pipe jacking machine is achieved.

[0065] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A pipe jacking construction method for complex strata with sudden changes in strata, characterized in that: The construction steps include: A pipe shed (1) is constructed on the outer contour of the top of the tunneling cross section to provide support for the top of the tunneling cross section; Dividing the excavation cross section into a rock layer area (2) and a soft soil area (3), arranging positioning drilling holes (4) in the rock layer area (2), and positioning grouting reinforcement holes (5) in the soft soil area (3); Horizontally drilling a hole in the rock formation area (2) according to the positioning point of the drilling hole (4); after the drilling of the drilling hole (4) is completed, injecting a mixed slurry of bentonite and slaked lime into the drilling hole (4) to fill the drilling hole (4) to achieve replacement of the strata in the rock formation area (2); Performing horizontal high-pressure jet grouting pile construction at each grouting reinforcement hole (5) in the soft soil area (3) to achieve reinforcement of the soft soil area (3); After the soft soil area (3) and the rock layer area (2) are prepared, tunneling is carried out along the tunneling route using a pipe jacking machine.

2. The method for pipe jacking in complex strata with sudden changes in strata according to claim 1 is characterized in that: The drilling and grouting of the drilling hole (4), as well as the construction of horizontal high-pressure jet jet piles from the grouting reinforcement hole (5) into the stratum can be carried out according to the principle of approaching from both ends of the excavation route to the middle.

3. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1 is characterized in that: When drilling the borehole (4), if a stratum change is encountered, drilling should be stopped, and grouting should be injected at the end of the borehole (4) to seal the end of the borehole (4).

4. The method for pipe jacking in complex strata with sudden changes in strata according to claim 1 is characterized in that: During the drilling process of the drilling hole (4), if the water output of a single hole is less than 30L / min, drilling can continue; if the water output of a single hole is greater than 30L / min, drilling should be stopped immediately and grouting should be carried out to seal the hole.

5. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1 is characterized in that: The arrangement spacing of the drilling holes (4) at the outer edge of the rock formation area (2) is denser than that in the middle area of ​​the rock formation area (2).

6. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1 is characterized in that: After the drilling of the drilling holes (4) is completed, all the drilling holes (4) are pressure tested with clean water. After the pressure test is completed, the pressure is slowly increased and grouting is performed. After the grouting is completed, the pressure is re-pressurized until the slurry is fully diffused and penetrated, and then the hole sealing operation is performed.

7. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1 is characterized in that: The drilling area of ​​the drilling hole (4) covers the interface between the rock layer area (2) and the soft soil area (3).

8. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1 is characterized in that: Before the soil layer transformation construction in the rock layer area (2) and the soft soil area (3) is carried out, a construction step is included in which settlement monitoring points are arranged on the ground above the excavation route, and the settlement monitoring points are densely distributed at the pipeline.

9. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 1, characterized in that: When using a pipe jacking machine to advance forward, the pipe jacking machine uses a composite cutter disc that is a combination of a tearing knife, a shell knife and a fishtail knife.

10. The method for pipe jacking construction in complex strata with sudden changes in strata according to claim 9, characterized in that: The composite cutter disc is arranged as a 6-spoke type, with a reinforcement ring arranged on the outer edge and the middle of the spoke, tearing knives arranged on both sides of the spoke, heavy tearing knives arranged on the ends, a shell knife made of large alloy arranged in the middle, a fishtail knife arranged in the middle of the cutter disc, and a scraper with wear-resistant welding is arranged on the shell of the pipe jacking machine.

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