Construction method of rectangular jacking pipe receiving in hard rock

Abstract

The present invention provides a construction method for receiving a rectangular jacking pipe when encountering hard rock. The method first determines the scope of the excavation and removal area, reversely excavates the soil within the removal area using an excavator in the receiving well, and finally pushes the jacking machine to the receiving well to complete the reception. The excavation and removal area includes the hard rock receiving construction section from the start to the tunnel portal along the pipeline line section in the hard rock receiving area, and the hard rock receiving upper soil located in the hard rock receiving construction section. The reserved face soil and the middle reserved core soil are reserved in the hard rock receiving construction section. The reserved face soil extends from the start of the hard rock receiving construction section along the pipeline line section toward the tunnel portal, and the middle reserved core soil extends from the end of the reserved face soil extension along the pipeline line section toward the tunnel portal. Furthermore, when the excavator reversely excavates, the upper hard rock receiving soil is first removed, and then the hard rock receiving construction section is removed. The present invention can achieve safe and rapid construction, reduce project costs, and strictly control construction settlement.

Description

Technical Field

[0001] The invention relates to the technical field of pipe jacking construction, and in particular to a receiving construction method for a rectangular pipe jacking construction when a pipe jacking machine encounters hard rock during receiving. Background Art

[0002] Pipe jacking is a method of underground pipeline construction that developed after shield tunneling. Because this construction method requires no surface excavation and can cross railways, highways, rivers, surface buildings, underground structures, and various underground pipelines, it has become a primary method for non-open-cut construction of urban underground pipe sections, finding widespread application in water supply and drainage, sewage treatment, communications, and power pipelines. The main operating principle of pipe jacking is to use the thrust of a main jacking cylinder and inter-pipeline relays to push a tool pipe or tunnel boring machine from a working shaft through the soil and into a receiving shaft where it is hoisted. Simultaneously, the pipeline immediately behind the tool pipe or tunnel boring machine is buried between the two shafts, successfully completing the excavation and laying of the underground pipeline. With the growing demand for urban integrated pipeline corridor construction, many overhead lines are being converted to underground cables; high-voltage cables often cross roads. Furthermore, due to dense urban construction, many areas lack the conditions for excavation, leading to the increasing use of pipe jacking technology.

[0003] The specific process of the pipe jacking construction technology is as follows: during construction, a pipe jacking working well and a receiving well are first made at both ends of the target construction section as the starting point and end point of a section of pipe jacking. A reserved hole is provided on one or both sides of the well wall in the working well as the outlet of the pipe jacking machine. The well wall opposite it is the pressure-bearing wall. The front side of the pressure-bearing wall is installed with a pipe jacking jack and a pressure pad (also called a steel backrest). The jack can push the pipe jacking machine out of the reserved hole in the working well, and then use the pipe jacking machine as a guide to push the prefabricated pipe section into the soil layer according to the design axis, section by section, until the first pipe section behind the pipe jacking machine enters the reserved hole in the receiving well, and the construction of a section of pipeline is completed. In order to carry out pipe jacking construction over a longer distance, one to several relay rooms can be set in the middle of the pipeline as relay jacking, and lubricating mud can be injected around the outer periphery of the pipeline. Pipe jacking construction can be used for straight pipelines as well as for complex pipelines such as curves.

[0004] With the accelerated introduction and active innovation of pipe jacking technology in my country, the technology has achieved rapid development and progress, with breakthroughs in diameter, adaptability, digitalization, high precision, and construction length. However, at present, pipe jacking technology in my country still faces many unresolved technical issues and bottlenecks. The most prominent problem is the relatively backward technology of mechanical equipment. my country's pipe jacking machinery and equipment are mainly imported. Although there are domestic manufacturers, the overall technology lags behind international advanced levels. The variety of pipe jacking machines is insufficient to meet the diverse needs of projects. In particular, there are no rock jacking machines suitable for medium-strength rock formations and above. The soil type is narrow, and the durability, mechanization, and automation levels are insufficient. These factors limit the application of pipe jacking machinery and equipment in many different regions of my country, with significant regional differences. For example, due to the prevalence of medium- and high-strength soil and rock formations in western and central-western my country, only a few West-East Gas Pipeline projects have adopted pipe jacking for crossings. Its application in urban areas is also greatly limited. Mechanized pipe jacking is often not the preferred method, and hand-dug pipe jacking still accounts for the largest proportion.

[0005] Especially during the receiving process of pipe jacking construction, since the receiving well portion often requires the selection of a relatively solid soil stratum for construction, and the surrounding soil is often reinforced during the construction process to ensure the stability of the receiving well, pipe jacking often encounters hard rock in the area around the receiving well. The strata in the receiving area are significantly different from those in the central tunnel area. Generally speaking, the strata in the central tunnel area are mainly clay, soft soil, silty clay, silty sand, gravel, and pebble layers. The overall soil is relatively soft and easy to cut, belonging to medium-to-low strength soil. Independent cutting and mixing cutterheads can be used for excavation, which has a fast advancement speed, high construction efficiency, and minimal ground subsidence (excellent operators can control it within 10mm). However, the disadvantage is that construction cannot be carried out when encountering medium-to-high strength hard rock in the receiving area. At this time, if the cutterhead is replaced with one suitable for medium-to-high strength rock formations, the construction period will be greatly extended. If, however, a cutterhead suitable for medium- to high-strength rock formations is used throughout the construction process, for example, one with spoke-shaped cutting blades welded to the cone of the shell's soil bin, and featuring a sturdy and wear-resistant cutting head, this type of cutterhead has a very wide range of applications. In addition to crushing high-hardness rock, it also ensures that muddy water from the intake pump can consistently reach the soil bin through the gaps, ensuring proper operation not only in high-hardness rock and large pieces of gravel, but also in clay. However, the downsides are slow jacking speeds, difficulty controlling excavation volume when encountering quicksand, and significant construction settlement. Especially when large rocks and strongly weathered rock are present in the pipe jacking machine's receiving area, construction timelines, costs, and settlements cannot be adequately controlled.

[0006] Therefore, in most current working conditions, the pipe jacking machine construction method is suitable for tunnel construction in soft soil and some small amounts of hard rock (uniaxial compressive strength less than 60MPa). Conventional pipe jacking machine reception is that the cutterhead of the pipe jacking machine cuts the stratum to achieve normal excavation reception. However, if the stratum in the receiving area is a high-strength rock stratum (uniaxial compressive strength exceeds 60MPa) during excavation reception, and the hard rock covers a large area that exceeds the size of the pipe jacking machine, conventional cutterhead excavation reception will cause cutterhead excavation difficulties, large cutterhead wear, and the need to open the chamber to change cutters within a short distance. The excavation speed is slow, and the construction cost of this type of project is relatively high. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention provides a construction method for rectangular jacking pipe receiving in hard rock, which can effectively solve the problems of difficulty or inability of cutterhead excavation caused by high-strength hard rock encountered during construction in the jacking pipe receiving area. Without opening the warehouse to replace the cutterhead, safe and fast construction can be carried out, effectively reducing the construction cost of the project, and strictly controlling construction settlement, ensuring the safety and stability of the construction project.

[0008] The technical solutions adopted by the present invention are as follows.

[0009] A construction method for receiving a rectangular jacking pipe in hard rock, comprising the following steps:

[0010] S1: Determine the scope of the excavation and removal area based on the scope of the hard rock receiving area of ​​the pipe jacking machine;

[0011] S2: Use the excavator in the receiving well to reversely excavate and remove the soil in the area;

[0012] S3: Push the pipe jacking machine to the receiving well to complete the receiving of the pipe jacking machine.

[0013] Among them, the excavation and removal area includes the hard rock receiving construction section from the start of the pipeline line section to the tunnel portal in the hard rock receiving area, and the hard rock receiving upper soil located in the hard rock receiving construction section, and reserved soil for the tunnel face and reserved core soil in the middle are reserved in the hard rock receiving construction section. The reserved soil for the tunnel face extends from the start of the hard rock receiving construction section along the pipeline line section toward the tunnel portal, and the reserved core soil in the middle extends from the end of the extension of the reserved soil for the tunnel face along the pipeline line section toward the tunnel portal; and when the excavator excavates in the reverse direction, the upper soil of the hard rock receiving is first broken, and then the hard rock receiving construction section is broken.

[0014] In step S1, the scope of the excavation and removal area is determined according to the scope of the hard rock receiving area of ​​the pipe jacking machine, specifically including: conducting a detailed survey of the geological conditions of the pipe jacking machine receiving area, and identifying the area where the uniaxial compressive strength of the stratum soil exceeds 60MPa as the hard rock receiving area.

[0015] In step S1, it is determined that the length of the hard rock receiving area along the pipeline line exceeds 5 meters.

[0016] In step S2, after the front edge of the cutter head of the pipe jacking machine stops at the starting position along the pipeline line section in the hard rock receiving area, a layered excavation method is adopted, and the upper soil of the hard rock receiving area and the hard rock receiving construction section are excavated in sequence using an excavator.

[0017] In step S2, the hard rock receiving upper soil body is in a slope structure with a slope ratio of 1:0.3 to 1:0.7, and the slope surface is reinforced and supported; when the excavation depth of the foundation pit for the hard rock receiving upper soil body is ≤10m, a soil nail wall reinforcement and support method is adopted; when the excavation depth of the foundation pit for the hard rock receiving upper soil body is greater than 10m, an anchor rod + soil nail wall reinforcement and support method is adopted.

[0018] Furthermore, the soil nail grouting material for forming the soil nail wall is PO 42.5 ordinary Portland cement slurry with a water-cement ratio of 0.5 to 0.55 and a strength grade of not less than 20 MPa.

[0019] In step S2, the hard rock receiving construction section is excavated in the tunnel portal by a blasting hammer of an excavator in a zoned excavation manner; the specific zoned excavation manner is that the left area and the right area are excavated successively in the tunnel portal, and the area division of the left area and the right area is separated by the middle reserved core soil. The two areas are excavated from the tunnel portal to the end of the soil reserved at the tunnel face, and then the length section of the middle reserved core soil at the tunnel portal is excavated and broken, and the length of the middle reserved core soil is retained to the required length.

[0020] In step S2, the width of the reserved soil at the reserved face is H1 = 0.05L to 0.15L, the width of the reserved core soil in the middle is H2 = 1 / 3L to 1 / 2L, the length of the reserved core soil in the middle is L2 > 3m, preferably L2 = 3 to 5m, and when H2:H1 = 4 to 8, L is the width inside the portal, and the heights of the reserved soil at the reserved face and the reserved core soil in the middle are both consistent with the height of the portal.

[0021] In step S2, when the excavator reversely excavates and removes the soil in the area, the debris generated during the excavation and removal process is cleaned in a timely manner, including the debris generated when the hard rock receiving upper soil and the hard rock receiving construction section are constructed successively. A ground crane and a soil bucket truck are set on the receiving well to vertically lift the soil out.

[0022] In step S3, the excavator is first transported out of the receiving well, and then the receiving work of the pipe jacking machine is started; the hydraulic cylinder jack is started to push the pipe jacking machine from the stop position to continue excavating along the pipeline line section toward the tunnel portal, and the reserved soil of the reserved face and the reserved core soil in the middle are broken in turn, until the pipe jacking machine is pushed out of the tunnel portal and pushed into the receiving well to complete the receiving.

[0023] In step S3, the advancement speed of the pipe jacking machine in the breaking area is 5 to 15 mm / min.

[0024] In step S3, after the pipe jacking machine completes the receiving, the following steps are also included: the pipe jacking machine is dismantled and moved out of the receiving well, and then the space part of the hard rock receiving upper soil body that is excavated and broken is backfilled with soil, and part of the original soil generated and hoisted during the reverse excavation process of the excavator is backfilled into the space of the hard rock receiving upper soil body until the ground elevation, and the gap between the pipe jacking machine segments and the surrounding soil layer is filled with waterproof mortar or fine stone concrete.

[0025] The present invention adopts the reverse excavation of an excavator to break the target hard rock receiving area, and solves the problems of travel difficulty, cutter head wear, soil discharge jam, and pipe jacking machine damage caused by forcibly pushing the pipe jacking machine to receive the hard rock when the rectangular pipe jacking machine receives the hard rock. Compared with the blasting technology, the invention has small vibration, small impact, less dust, less pollution, and is green and environmentally friendly; there is no need to replace the cutter head, which greatly shortens the construction period and reduces the construction cost; at the same time, through the pre-excavation of the upper soil of the hard rock receiving area, and the joint design of the reserved soil of the face and the reserved core soil in the middle, the stability of the construction of the hard rock receiving area is maintained, and the settlement is effectively controlled to be maintained below 10mm while accelerating the construction, ensuring the safety of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The technical solutions of the embodiments of the present invention are further described in detail below through the accompanying drawings and examples.

[0027] Figure 1 It is a schematic diagram of the construction structure of the rectangular jacking pipe receiving in the hard rock receiving construction area of ​​the present invention.

[0028] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure of the AA part.

[0029] Figure 3 This is a structural schematic diagram of the portal portion of the rectangular jacking pipe receiving construction area in the hard rock receiving area of ​​the present invention.

[0030] Figure 4 The following is a schematic diagram of the settlement monitoring results in the engineering example of the present invention. Each curve in the figure represents the settlement change of a monitoring point.

[0031] in,

[0032] 1-Hard rock receiving construction section; 2-Upper hard rock receiving soil; 3-Reserved soil at the tunnel face; 4-Reserved core soil in the middle; 5-Receiving well; 6-Tunnel portal; 7-Pipe jacking machine; 8-Cutterhead; 9-Segments; 10-Excavator; 11-Left area; 12-Right area. DETAILED DESCRIPTION

[0033] The present invention will be further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the scope of protection of the present invention.

[0034] The invention provides a construction method for receiving a rectangular jacking pipe in hard rock, such as Figure 1-3 As shown, it mainly includes the following steps:

[0035] First, determine the scope of the excavation and removal area based on the scope of the hard rock receiving area of ​​the pipe jacking machine 7;

[0036] Second, the excavator 10 in the receiving well 5 reversely excavates and removes the soil in the area;

[0037] Third, push the pipe jacking machine 7 to the receiving well 5 to complete the receiving of the pipe jacking machine 7.

[0038] In the above steps, the excavation and removal area includes the hard rock receiving construction section 1 from the start of the pipeline line section to the tunnel portal 6 in the hard rock receiving area, and the hard rock receiving upper soil 2 located in the hard rock receiving construction section 1, and the tunnel face reserved soil 3 and the middle reserved core soil 4 are reserved in the hard rock receiving construction section 1. The tunnel face reserved soil 3 extends from the start of the hard rock receiving construction section 1 along the pipeline line section toward the tunnel portal 6, and the middle reserved core soil 4 extends from the end of the extension of the tunnel face reserved soil 3 along the pipeline line section toward the tunnel portal 6; and when the excavator 10 excavates in the reverse direction, the hard rock receiving upper soil 2 is first removed, and then the hard rock receiving construction section 1 is removed.

[0039] The above-mentioned construction scheme of the present invention enables the pipe jacking machine 7 to be unable to advance when encountering hard rock by adopting the method of reverse excavation and breaking by the excavator 10 from the receiving end of the receiving well 5 when the pipe jacking construction encounters a hard rock area, thereby eliminating the tedious process of replacing the cutter head 8 and preventing problems such as damage to the cutter head 8 caused by forced excavation, thereby greatly improving construction efficiency and speed. Taking into account the high construction intensity of the reverse excavation construction of the excavator 10, which may lead to a reduction in the stability of the soil in the excavation and demolition area, affecting the safety and stability of the construction project, and may also cause large engineering settlement. Therefore, in the process design, on the one hand, it is necessary to first demolish the hard rock receiving upper soil 2, and then carry out the demolition work of the hard rock receiving construction section 1, to prevent the construction section from collapsing or excessive settlement and deformation due to the existence of the hard rock receiving upper soil 2 when the hard rock receiving construction section 1 is demolished. On the other hand, the reserved face reserved soil 3 and the middle reserved core soil 4 are specially designed, which can further ensure the construction safety of the reverse demolition of the excavator 10 and the stability of the hard rock receiving construction section 1, and realize the effective control of the overall settlement in the hard rock receiving area of ​​the pipe jacking machine 7.

[0040] In the above steps, the scope of the excavation and demolition area is determined based on the scope of the hard rock receiving area of ​​the pipe jacking machine 7. Specifically, the following steps are performed: a detailed geological survey of the receiving area of ​​the pipe jacking machine 7 is conducted, and areas where the uniaxial compressive strength of the stratum soil exceeds 60MPa are identified as the hard rock receiving area. For conventional pipe jacking machines 7 suitable for medium- and low-strength strata, when the length of the hard rock receiving area along the pipeline exceeds 5m, continued excavation of the pipe jacking machine 7 may cause adverse effects such as difficulty in moving the pipe jacking machine 7, inappropriate extension of the construction period, damage to the cutterhead 8, and increased construction costs. In this case, after comprehensive consideration, the subsequent construction plan of the present invention can be adopted for excavation and demolition.

[0041] In the above steps, after the front edge of the cutter head 8 of the pipe jacking machine 7 stops at the starting position along the pipeline line section in the hard rock receiving area (i.e., the starting position of the hard rock receiving construction section 1), the excavator 10 can be used to first start the excavation of the hard rock receiving upper soil 2. The hard rock receiving upper soil 2 is a slope structure with a slope ratio (cross-section slope height: slope width) of 1:0.3 to 1:0.7. The slope structure can effectively prevent collapse and landslides during subsequent construction. In order to further improve the stability of the slope structure, the slope surface can also be reinforced and supported. When the excavation depth of the foundation pit of the hard rock receiving upper soil 2 is ≤10m, a soil nail wall reinforcement support method can be used. When the excavation depth of the foundation pit of the hard rock receiving upper soil 2 is >10m, an anchor rod + soil nail wall reinforcement support method can be used. The soil nail grouting material used to form the soil nail wall can be PO 42.5 ordinary Portland cement slurry with a water-cement ratio of 0.5-0.55 and a strength grade of no less than 20 MPa. This material is particularly suitable for reinforcing and protecting hard rock formations with strengths exceeding 60 MPa under the high-intensity construction conditions of excavator 10, and is highly compatible with high-strength hard rock. Excavation and removal of the upper hard rock receiving soil mass 2 is performed using excavator 10 in a layered excavation method, with each layer being excavated 3±1 m to the top elevation of portal 6. This layered excavation method facilitates structural stability during the excavation process.

[0042] In the above steps, after the excavation and reinforcement support of the hard rock receiving upper soil 2 are completed, the excavation of the hard rock receiving construction section 1 can be carried out, and the excavation can be carried out in a zoned excavation manner in the tunnel portal 6 using the blasting hammer of the excavator 10. The specific zoned excavation method can be to excavate the left area 11 and the right area 12 in the tunnel portal 6 respectively. The area division of the left area 11 and the right area 12 can be separated by the middle reserved core soil 4. The two areas are excavated from the tunnel portal 6 to the end of the soil 3 reserved for the face, and then the middle reserved core soil 4 is excavated and removed for the length section at the tunnel portal 6. The length of the middle reserved core soil 4 can be retained to the required length. Finally, the surrounding soil in the excavated and removed area can be trimmed as needed.

[0043] In the above steps, the reserved face reserved soil 3 and the middle reserved core soil 4 are used to jointly maintain the stability of the ground soil within the excavation and demolition area, especially the stability of the soil above the pipe jacking machine 7. The reserved face reserved soil 3 can not only reduce the initial disturbance of the ground soil caused by the pipe jacking machine 7 when it starts to advance after the excavator 10 completes reverse excavation, but also effectively maintain the stability of the initial advancement of the pipe jacking machine 7 when it starts to receive. The middle reserved core soil 4 also improves the stability of the reserved face reserved soil 3. In order to optimize the settlement control standard within the excavation and demolition area and keep the ground settlement within 10 mm, the reserved range of the reserved face reserved soil 3 and the middle reserved core soil 4 can be further optimized and controlled. According to the characteristics of the soil in hard rock formations above 60 MPa and the construction strength experience of the excavator 10, under the settlement control standard requirements, it is found that the width of the reserved soil 3 of the reserved face is H1 = 0.05L ~ 0.15L, the width of the middle reserved core soil 4 is H2 = 1 / 3L ~ 1 / 2L, the length of the middle reserved core soil 4 is L2 > 3m, preferably L2 = 3 ~ 5m, and H2:H1 = 4 ~ 8, which can meet the requirements, where L is the width inside the tunnel portal 6, and the heights of the reserved soil 3 of the reserved face and the middle reserved core soil 4 are consistent with the height of the tunnel portal 6 ( Figure 2 If the width H1 of the reserved soil 3 of the reserved tunnel face is too large, it will be detrimental to the excavation when the pipe jacking machine 7 receives it, and the cutter head 8 will have difficulty in cutting and the tool will wear too much. If the width H1 is too small, it will be detrimental to the stability of the stratum soil within the excavation and removal area. Similarly, if the width H2 of the central reserved core soil 4 is too large or the length L2 is too long, it will be detrimental to the excavation when the pipe jacking machine 7 receives it, or it will cause unnecessary excessive wear of the tool. If the width H2 is too small or the length L2 is too short, it will be detrimental to the stability of the stratum soil and the coordination stability of the reserved soil 3 of the reserved tunnel face, and it will easily cause the collapse of the reserved soil 3 of the reserved tunnel face when the pipe jacking machine 7 excavates the reserved soil 3 of the reserved tunnel face.

[0044] In the above steps, when the excavator 10 reversely excavates and removes the soil in the area, the debris generated during the excavation and removal process should be cleaned up in time, including the debris generated when the hard rock receiving upper soil 2 and the hard rock receiving construction section 1 are constructed. A ground crane and a soil bucket truck can be set on the receiving well 5 to vertically lift the soil out.

[0045] In the above steps, after the excavator 10 reversely excavates and removes the soil in the area, the excavator 10 is transported out of the receiving well 5, and the receiving work of the pipe jacking machine 7 can continue. Start the hydraulic cylinder jack, and push the pipe jacking machine 7 from the stop position along the pipeline line section to the tunnel portal 6, and successively remove the reserved soil 3 of the reserved face and the reserved core soil 4 in the middle, until the pipe jacking machine 7 is pushed out of the tunnel portal 6 and pushed into the receiving well 5 to complete the reception. In order to control the excavation construction intensity during the receiving process, reduce the disturbance to the stratum soil and meet the settlement standard design requirements, the propulsion speed of the pipe jacking machine 7 in the removal area should be controlled at 5 to 15 mm / min. The thrust of the lower hydraulic jack of the pipe jacking machine 7 can also be slightly greater than the thrust of the upper hydraulic jack to maintain the overall propulsion balance of the propulsion surface.

[0046] In the above steps, after the pipe jacking machine 7 completes the receiving process, it is dismantled and removed from the receiving well 5. The space above the hard rock receiving soil 2, which was excavated and broken, is then backfilled with soil. Some of the original soil generated and hoisted during the reverse excavation process by the excavator 10 can be backfilled into the space above the hard rock receiving soil 2 to ground level. The gaps between the pipe segments 9 of the pipe jacking machine 7 and the surrounding soil are filled with waterproof mortar or fine stone concrete to ensure a tight and secure connection between the pipe segments 9 and the surrounding strata.

[0047] In order to further illustrate the design advantages of the construction method of the present invention, a construction project in a certain place is used as an example to illustrate it.

[0048] The Yongxing Hebei Road (Daguan Expressway to Cida Road) road and integrated pipe corridor project (Section 5), a municipal transportation supporting project in the Beijing New Airport Linkong Economic Zone, involves the pipe corridor passing under the Daguan Expressway at K0+414.300 to K0+542.700. The project was constructed using a rectangular pipe jacking method. The pipe jacking machine 7, with a size of 9.1m (L)*5.5m, advanced uphill from east to west with a slope of 0.2%. The actual length of the pipe jacking machine 7 was 129m. When the pipe jacking machine 7 reached the pipe receiving area, the bedrock within 10m of the receiving well 5 was relatively shallow, with some sections consisting of moderately to slightly weathered granite and conglomerate. The core sampling strength report showed a uniaxial compressive strength of up to 80MPa.

[0049] If the pipe jacking machine 7 is used to continue to push and receive according to the original method, the jacking speed of the pipe jacking machine 7 is slow, and the wear of the cutter is inevitable. After a small number of cutters are worn, if they are not discovered and replaced in time, the wear rate of other cutters on the cutter head 8 will be greatly accelerated. At the same time, the cutter head 8 is heavily loaded, and cement blocks are stuck between the cutter head 8 and the face, affecting mixing. Cement blocks block the spiral excavator pipe, making excavation difficult, which will seriously affect the smooth reception of the pipe jacking machine 7. If the tool is changed by opening the warehouse, it will greatly affect the construction period and greatly increase the cost of tool change. After organizing experts to conduct internal discussions and demonstrations, the results of the impact of the acceptance method of opening the warehouse to change the tool on the construction period and cost are listed in Table 1. At the same time, after internal discussions and demonstrations by the expert group, it can be adopted the construction acceptance method of the above-mentioned excavator 10 reverse excavation of the present invention, which can greatly save construction period and cost. The construction period and cost savings after successful construction using the acceptance method of the present invention are also listed in Table 1.

[0050] Table 1 Comparison results of opening and changing tools in the engineering example and the two receiving methods of the pipe jacking machine of the present invention

[0051]

[0052]

[0053] The receiving method of the present invention was used for confidential construction within the area. The specific construction process was as follows: an excavator 10 was used to excavate the upper hard rock receiving soil 2 layer by layer, excavating each 3m layer to the top elevation of the portal 6. The foundation pit was supported by soil nailing walls, with a slope of 1:0.4. Four rows of drilled and cast-in-place soil nails were installed in a plum blossom pattern, with horizontal spacing of 1.3m and vertical spacing of 1.4m. The excavator 10 then used a blasting hammer to successively break the soil layers in the left area 11 and right area 12 of the hard rock receiving construction section 1 along the portal 6, breaking them layer by layer from top to bottom. During the breaking process, attention was paid to the maintenance of the soil side walls within the breaking area and the portal 6, which facilitated strict control of the ground elevation and ensured a smooth and flat ground surface. Excavation and breaking of the central reserved core soil 4, along the length of the portal 6, was then carried out. The reserved soil 3 at the tunnel face in front of the cutterhead 8 of the pipe jacking machine 7 is cut by the pipe jacking machine 7. The width H1 of the reserved soil 3 at the tunnel face is 500mm. The length L2 of the reserved core soil 4 in the middle should be controlled to 3.5m, and the width H2 is 3.5m. The height is consistent with the height of the portal 6, which can maintain the stability of the soil layer above the pipe jacking machine 7. During the construction process, the debris generated by the demolition of the receiving well 5 is cleaned and vertically lifted out of the excavation using a ground crane and a soil bucket truck. After the excavator 10 completes the demolition, it pushes the hydraulic cylinder jack to demolish the reserved soil 3 at the tunnel face and the reserved core soil 4 in the middle, and pushes the pipe jacking machine 7 to the receiving well 5. The pushing speed is controlled at about 10mm / min. The excavated soil is backfilled onto the pipe segments 9 (or pipe sections) until the ground level. The gaps between the pipe segments 9 of the pipe jacking machine 7 and the surrounding soil layers are filled with waterproof mortar.

[0054] The construction of the hard rock section encountered by the jacking machine 7 in this project started on December 19, 2019 and ended on December 26, 2019. The jacking machine 7 in this section was successfully completed and the pipe section was pushed to the set position. In order to accurately monitor and control the settlement, multiple representative settlement monitoring points were selected within the construction area. The monitoring results showed that ( Figure 4 ), the ground settlement is precisely controlled within 10mm, the ground settlement is small, the construction period is short, the environmental impact is small, and it has good economic and environmental benefits.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A construction method for receiving a rectangular jacking pipe in hard rock, comprising: S1: Determine the scope of the excavation and removal area according to the scope of the hard rock receiving area of ​​the pipe jacking machine (7); S2: Excavating the soil in the area in reverse direction by the excavator (10) in the receiving well (5); S3: Push the pipe jacking machine (7) to the receiving well (5) to complete the receiving of the pipe jacking machine (7); The excavation and removal area includes a hard rock receiving construction section (1) from the start of the pipeline line section to the tunnel portal (6) in the hard rock receiving area and a hard rock receiving upper soil body (2) located in the hard rock receiving construction section (1), and reserved face soil body (3) and middle reserved core soil body (4) are reserved in the hard rock receiving construction section (1). The face reserved soil body (3) extends from the start of the hard rock receiving construction section (1) along the pipeline line section to the tunnel portal (6), and the middle reserved core soil body (4) extends from the end of the extension of the face reserved soil body (3) along the pipeline line section to the tunnel portal (6); and when the excavator (10) excavates in the reverse direction, the hard rock receiving upper soil body (2) is first removed, and then the hard rock receiving construction section (1) is removed.

2. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1 is characterized in that: In the step S1, the scope of the excavation and removal area is determined according to the scope of the hard rock receiving area of ​​the pipe jacking machine (7), specifically comprising: conducting a detailed survey of the geological conditions of the receiving area of ​​the pipe jacking machine (7), and identifying the area where the uniaxial compressive strength of the stratum soil exceeds 60 MPa as the hard rock receiving area; In step S1, it is determined that the length of the hard rock receiving area along the pipeline line exceeds 5 meters.

3. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1 is characterized in that: In step S2, after the front edge of the cutterhead (8) of the pipe jacking machine (7) is stopped at the starting position along the pipeline line section in the hard rock receiving area, a layered excavation method is adopted, and the excavator (10) is used to successively excavate the hard rock receiving upper soil (2) and the hard rock receiving construction section (1).

4. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1 is characterized in that: In the step S2, the hard rock receiving upper soil body (2) is in a slope structure with a slope ratio of 1:0.3 to 1:0.7, and the slope surface is reinforced and supported; when the excavation depth of the foundation pit of the hard rock receiving upper soil body (2) is ≤10m, a soil nail wall reinforcement and support method is adopted; when the excavation depth of the foundation pit of the hard rock receiving upper soil body (2) is greater than 10m, an anchor rod + soil nail wall reinforcement and support method is adopted; the soil nail grouting material for forming the soil nail wall is PO 42.5 ordinary Portland cement slurry with a water-cement ratio of 0.5 to 0.55 and a strength grade of not less than 20MPa.

5. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1 is characterized in that: In the step S2, the hard rock receiving construction section (1) is excavated in the tunnel portal (6) by using a blasting hammer of an excavator (10); the specific zoning excavation method is that the left area (11) and the right area (12) are excavated in sequence in the tunnel portal (6), and the area division of the left area (11) and the right area (12) is separated by the middle reserved core soil (4). The two areas are excavated from the tunnel portal (6) to the end of the reserved soil (3) of the tunnel face, and then the length section of the middle reserved core soil (4) at the tunnel portal (6) is excavated and broken, and the length of the middle reserved core soil (4) is retained to the required length.

6. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1 is characterized in that: In the step S2, the width H1 of the reserved soil body (3) of the reserved tunnel face is 0.05L to 0.15L, the width H2 of the reserved core soil body (4) in the middle is 1 / 3L to 1 / 2L, the length L2 of the reserved core soil body (4) in the middle is greater than 3m, and when H2:H1=4 to 8, L is the inner width of the tunnel portal (6), and the heights of the reserved soil body (3) of the reserved tunnel face and the reserved core soil body (4) in the middle are consistent with the height of the tunnel portal (6).

7. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1, characterized in that: In step S2, when the excavator (10) reversely excavates and removes the soil in the area, the debris generated during the excavation and removal process is promptly cleaned, including the debris generated when the hard rock receiving upper soil (2) and the hard rock receiving construction section (1) are successively constructed, and the debris is vertically lifted out of the soil by arranging a ground crane and a soil bucket truck on the receiving well (5).

8. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1, characterized in that: In step S3, the excavator (10) is first transported out of the receiving well (5), and then the receiving work of the pipe jacking machine (7) is started; the hydraulic cylinder jack is started to push the pipe jacking machine (7) from the stopping position along the pipeline line section to continue excavating toward the tunnel portal (6), and the reserved soil body (3) of the reserved tunnel face and the reserved core soil body (4) in the middle are successively broken, until the pipe jacking machine (7) is pushed out of the tunnel portal (6) and pushed into the receiving well (5) to complete the receiving.

9. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1, characterized in that: In the step S3, the pushing speed of the pipe jacking machine (7) in the breaking area is 5 to 15 mm / min.

10. The construction method for receiving a rectangular jacking pipe in hard rock according to claim 1, characterized in that: In the step S3, after the pipe jacking machine (7) completes the receiving, the following steps are also included: the pipe jacking machine (7) is dismantled and moved out of the receiving well (5), and then the space portion of the hard rock receiving upper soil body (2) excavated and broken is backfilled with soil, and part of the original soil body generated and hoisted during the reverse excavation process of the excavator (10) is backfilled into the space of the hard rock receiving upper soil body (2) until the ground level, and the gap between the pipe segment (9) of the pipe jacking machine (7) and the surrounding soil layer is filled with waterproof mortar or fine stone concrete.

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