Construction method for pipe jacking machine head to exit a hole in case of receiving well unable to stop sinking

Abstract

The application discloses a construction method for pipe jacking machine head to exit a hole under the condition that a receiving well cannot stop sinking, and specifically comprises the following steps: steel sleeve box preparation, receiving well backfilling, steel sleeve box placing, steel sheet pile reinforcing, bottom sealing, steel sleeve box reinforcing, machine head positioning, horizontal hole construction and machine head hole exiting; the construction method places a vertical steel sleeve box in the receiving well, uses the mode of 'well-in-well', makes the steel sleeve box as a stable receiving well, provides an operation space for the pipe jacking machine head to enter the well, and successfully completes the pipe jacking machine head to enter the well; the method has low construction cost, short construction period, and is suitable for solving the problem that the pipe jacking machine head cannot exit a hole and be recovered due to the problem that the receiving well cannot be stabilized and cannot stop sinking.

Description

Technical Field

[0001] This invention relates to the field of pipe jacking construction engineering, specifically to the field of pipe jacking machine exiting the tunnel, and particularly to a construction method for the exit of the pipe jacking machine head when the receiving well cannot be stopped from settling. Background Technology

[0002] In my country, pipe jacking technology has become very mature, fully capable of constructing pipes with ultra-large diameters and ultra-long distances, effectively traversing various surface obstacles. Pipe jacking construction typically requires excavating two foundation pits, called the working pit and the receiving pit. The pipe jacking machine head is placed in the working pit and propelled through a pre-drilled opening in the working pit by the main jacking jacks and intermediate jacking machinery. It then penetrates the soil to reach the pre-drilled opening in the receiving pit, where it is retrieved, completing the pipe jacking construction.

[0003] However, if the receiving well is located in a complex urban environment adjacent to various surface structures, even after the underwater sealing concrete and high-pressure jet grouting piles have been reinforced, the receiving well may be subject to significant disturbance before reaching its designed strength due to various dynamic and static loads (silt in groundwater-retaining sand and silt layers is highly susceptible to liquefaction from vibration). This can lead to the receiving well failing to reach its design strength, resulting in instability and settlement issues. Consequently, it may not meet the requirements for the pipe jacking machine to exit the tunnel and be retrieved, affecting project progress and quality. In existing technologies, if these problems arise, the only option is to excavate the foundation pit again and rebuild the receiving well. This delays the construction period and increases costs, clearly hindering the large-scale application of pipe jacking technology. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing methods for solving the problem of unstable and unsettled receiving wells, which are characterized by long construction periods and high costs. This invention proposes a construction method for the exit of the pipe jacking head when the receiving well cannot be stabilized. This method involves placing a vertical steel casing inside the receiving well, utilizing a "well-within-a-well" structure. This allows the steel casing to function as a stable receiving well, providing operating space for the pipe jacking head to enter the well, thus facilitating its successful entry. This method has low construction costs and a short construction period, making it suitable for situations where the pipe jacking head cannot be exited or retrieved due to the instability and inability to stabilize the receiving well.

[0005] To achieve the above-mentioned objective, this invention provides a construction method for the pipe jacking machine head to exit the tunnel when the receiving well cannot be stopped from settling, comprising the following steps:

[0006] Step 1: Prepare the steel casing according to the size of the pipe jacking machine head and the depth of the receiving well;

[0007] Step 2: Backfill the receiving well; the backfill height is less than the height of the steel casing.

[0008] Step 3: Determine the position of the vertically placed steel casing based on the position of the pipe jacking machine head's extension line inside the receiving shaft, and place the steel casing.

[0009] Step 4: Use steel sheet piles to isolate the area around the steel caisson;

[0010] Step 5: Clean the mud from the bottom of the steel casing and the partition, and seal the bottom.

[0011] Step 6: Perform curing treatment on the bottom seal. After curing, clean the inside of the steel casing and reinforce it.

[0012] Step 7: Drill holes based on the approximate center position of the pipe jacking head obtained from the measurement to confirm the actual position of the pipe jacking head;

[0013] Step 8: Based on the actual position of the pipe jacking head confirmed by drilling, enlarge and trim the hole until the face cutterhead of the pipe jacking head is fully exposed in the transverse tunnel of the steel casing.

[0014] Step 9: Carry out pipe jacking construction until the pipe jacking machine head is completely inserted into the steel casing, and complete the exit of the pipe jacking machine head.

[0015] This invention discloses a construction method for the exit of a pipe jacking machine head when the receiving well fails to stop settling. The method involves placing a vertical steel casing inside the receiving well, using a "well-within-a-well" approach to make the vertical steel casing serve as a temporary receiving well. By backfilling the receiving well and reinforcing it with concrete sealing, both the receiving well and the steel casing are stabilized, allowing the steel casing to function as a stable receiving well and providing operating space for the pipe jacking machine head to enter the well, thus facilitating its successful entry. This method has low construction costs and a short construction period, effectively solving the problem of pipe jacking machine head extraction failing to be retrieved due to various reasons after the receiving well has sunk to its designated position in complex urban environments.

[0016] Preferably, in step 1, the steel casing is a steel pipe with a wall thickness of not less than 10mm; the diameter of the steel casing is greater than the cross-sectional diameter and length of the pipe jacking machine head; the height of the steel casing is not greater than the depth of the receiving well and not less than half the depth of the receiving well; the preferred steel casing size is more convenient for construction and saves materials.

[0017] Preferably, the steel casing can be welded from multiple sections of steel pipe; welding can reduce costs and transportation difficulties.

[0018] Preferably, a support rod is also provided at the bottom of the steel casing; the support rod can prevent the steel casing from deforming due to surrounding pressure during placement.

[0019] Preferably, the support rods are arranged in a cross pattern; this preferred arrangement provides better support.

[0020] In step 2, backfilling can better stabilize the steel casing during placement, preventing displacement and affecting positioning. Alternatively, other methods can be used to achieve the backfilling effect, such as positioning piles or limiting plates. Most preferably, the backfilling can use the original soil, which can save transportation costs and shorten the construction period.

[0021] Preferably, the backfill height is 30-50cm less than the height of the steel casing; the preferred backfill height facilitates subsequent construction.

[0022] In step 3, the steel casing can be placed by using a counterweight and an excavator to press it down. When the frictional resistance is high (sinking is difficult), the resistance can be reduced by digging soil inside the steel casing. Alternatively, it can be combined with a vibratory pile driver to slowly vibrate and sink it.

[0023] In step 4, the zoning isolation treatment refers to using Larssen sheet piles to isolate the steel casing in different zones to reduce the lateral pressure of the surrounding soil on the steel casing and facilitate the zoning bottom sealing construction; Larssen sheet piles are used to reinforce the steel casing and the receiving well wall in different zones to prevent the inflow of external soil.

[0024] In step 5, preferably, when cleaning the soil in the steel casing and the bottom of the partition and sealing the bottom, the soil in areas A, B, C, and D are cleaned and sealed in sequence first, then the soil in areas E, F, and G are cleaned and sealed in sequence, and finally the soil in the steel casing is cleaned and sealed in sequence. The preferred cleaning and sealing sequence can better fix the steel casing and prevent deformation and displacement of the steel casing.

[0025] Preferably, when sealing the bottom within the zones, zones A, B, C, and D need to be sealed up to the top of the steel casing; the preferred degree of sealing can better ensure the safety and reliability of subsequent horizontal tunnel construction.

[0026] Preferably, the bottom surface of the steel casing is 20-40cm above the actual bottom elevation of the machine head; the expected height of the bottom surface and the bottom elevation of the machine head facilitates subsequent construction operations.

[0027] In step 6, the reinforcement treatment refers to welding at least one steel internal support inside the steel casing, above the predicted position line of the pipe jacking machine head; this is to prevent the steel casing from being deformed by external force during the construction of the horizontal tunnel after it has been cut.

[0028] In step 7, confirming the actual position of the drilling head means cutting on the steel casing according to the measured position and removing a small area of ​​the original well wall concrete to locate and determine the range of the drilling head.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. The construction method for the exit of the pipe jacking machine head in this invention involves placing a vertical steel casing inside the receiving well. Utilizing a "well-within-a-well" approach, the vertical steel casing acts as a temporary receiving well, providing stable space for the pipe jacking machine head to enter the well and ensuring its successful entry.

[0031] 2. The construction method of the pipe jacking machine head exiting the hole of the present invention has low construction cost and short construction period. It can effectively solve the problem that the receiving well fails to be sealed after sinking into place due to various reasons and the machine head cannot be taken out in complex urban environments. Attached image description:

[0032] Figure 1 This is a schematic diagram of the construction method flow in Embodiment 1 of the present invention;

[0033] Figure 2 This is a schematic cross-sectional view of the receiving well in Embodiment 1 of the present invention;

[0034] Figure 3 This is a top view of the receiving well in Embodiment 1 of the present invention;

[0035] Attached diagram descriptions: 1-Original receiving well; 2-Steel casing; 3-Pipe jacking machine head; 4-Steel sheet pile; 5-Backfill area; 6-Bottom sealing area; 7-Support rod. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0037] Example 1:

[0038] The construction method of this invention was applied to a pipeline project section 1 outside Jiaxing City. The project is designed to divert 230 million cubic meters of water annually. 3 The total length of the water transmission line is 171.6 km, of which 23.1 km is in Hangzhou and 148.5 km is in Jiaxing. This section (Pipeline Section 1) is located in Haining City, Jiaxing, and mainly consists of receiving wells, pipe jacking, and pipe laying works. The pipeline has two DN2200 pipes with a total length of 15.32 km.

[0039] In 5 # During the construction of the receiving well, it was discovered that 5 #The soil at the cutting edge of the receiving well is a thick layer of silty sand (elevation -2.89m to -15.19m, thickness 12.3m; the cutting edge of the receiving well is at elevation -9m, located in the middle of the silty sand layer). The surrounding stable groundwater level is around 3.0m. After the underwater sealing of the receiving well was completed, due to its proximity to the highway access road (the outer side of the receiving well wall is only 2m from the edge of the highway access road), the traffic volume is extremely high, and there are many heavy vehicles at night. The dynamic load of heavy vehicles passing at high speed has a significant impact on the pressure of the underground soil, causing the sealing concrete and high-pressure jet grouting piles to be significantly disturbed before reaching their designed strength or even before initial setting, ultimately failing to reach the design strength. During water pumping in the well, a large internal and external water pressure difference (approximately 10m height difference) will be formed due to the high groundwater level. The water flowing into the receiving well will cause the soil below the cutting edge of the receiving well to flow into the receiving well, resulting in the sinking of the receiving well and surface subsidence.

[0040] To ensure project quality and schedule while reducing costs, the construction method of this invention was adopted. The specific steps are as follows: Figure 1 , Figure 2 and Figure 3 ):

[0041] Step 1: The steel casing uses DN3600 steel pipe with a wall thickness of 20mm; the steel casing is divided into three sections. The first section is 2 meters long. A cross support of [16 channel steel is installed at the bottom of the steel base plate of the receiving well steel casing, and a grid support of [16 channel steel is installed at the top of the steel base plate; the second section of the receiving well steel casing is 2 meters long, and the third section is 3 meters long; the steel casing is connected by welding.

[0042] Step 2: In order to reduce the adverse effects of water floating during the construction of the steel casing, the original receiving well was backfilled with undisturbed soil before the steel casing was lowered. The backfill height was 40cm less than the design top elevation of the steel casing.

[0043] Step 3: After the original soil backfilling is completed, the steel casing hoisting and sinking construction will begin using an excavator and crane. The position of the vertical steel casing will be determined by the surveyors based on the position of the excavator head on the extension line inside the receiving well. The sinking will be carried out by using a counterweight and excavator to press down. When the frictional resistance is high (sinking is difficult), the soil inside the steel casing will be excavated to reduce the resistance and a vibratory pile driver will be used to slowly vibrate and sink it.

[0044] Step 4: After the steel casing is hoisted into the designated position and sunk into place, the steel casing is isolated in sections using 9m long Larssen steel sheet piles to reduce the lateral pressure of the surrounding soil on the steel casing and facilitate the section sealing construction; Larssen steel sheet piles are used to reinforce the section between the steel casing and the receiving well wall to prevent the inflow of external soil.

[0045] Step 5: After the steel caisson and Larssen sheet piles are constructed, the soil inside the steel caisson is cleaned with an excavator, and divers are deployed underwater to rinse the bottom of each section. First, sections A through D are rinsed and cleaned, then C30 underwater concrete is poured sequentially for bottom sealing. Sections A, B, C, and D are then filled with C20 underwater concrete up to the top of the steel caisson to ensure the safety and reliability of subsequent cross-tunnel construction. The remaining areas are then cleaned and sealed. After each area is completed and cured to a certain strength, underwater excavation and rinsing are carried out inside the steel caisson. After rinsing, C30 underwater concrete is poured for bottom sealing and reinforcement. Throughout the entire construction process, divers conduct underwater reconnaissance and promptly report the findings to guide the construction.

[0046] Step 6: After the underwater bottom sealing is completed and the water has been cured to the required age, the pumping operation inside the receiving well and steel casing will begin. After the pumping is completed, the inside of the steel casing will be cleaned and the internal support will be reinforced. The support is made of 16# H-shaped steel internal support, which is processed and welded to prevent the steel casing from being deformed by external force during the construction of the horizontal tunnel after it is cut.

[0047] Step 7: Arrange workers to cut according to the measured location, remove a small area of ​​the original well wall concrete, and locate and determine the range of the machine head;

[0048] Step 8: After the machine head is located, the horizontal opening is enlarged and repaired until the cutterhead facing the machine head is fully exposed inside the horizontal opening of the steel casing. At this point, the construction plan for the vertical steel casing is completed, and the machine head has sufficient operating space to enter the well.

[0049] Step 9: After the horizontal tunnel construction is completed, proceed with the pipe jacking construction until the pipe jacking machine head is fully inserted into the steel casing, and complete the exit of the pipe jacking machine head from the tunnel.

[0050] Main materials and equipment used:

[0051]

[0052]

[0053] Quality Standards:

[0054] The following standards shall be followed: "Code for Inspection and Evaluation of Construction Quality of Water Conservancy and Hydropower Projects" (SL176-2007), "Code for Construction and Acceptance of Water Supply and Drainage Pipeline Engineering" (GB50268-2008), and "Code for Construction of On-site Equipment and Industrial Pipeline Welding Engineering" (GB50236-2011).

[0055] Cost accounting:

[0056]

[0057] Construction period:

[0058] plan Construction period (days) Construction method of the present invention 15 Excavation method for foundation pit (estimated) 20

[0059] in conclusion:

[0060] The construction method of this invention can effectively save resources, reduce construction costs, shorten the construction period, and the construction technology is reliable, the mechanical equipment is simple, and it does not pollute the surrounding environment and atmosphere. It meets the relevant national environmental protection standards and has good energy-saving and environmental protection benefits. It is suitable for solving the problem of the inability to exit and recover the pipe jacking head due to the difficulty in stabilizing and stopping the sinking of the receiving well.

Claims

1. A construction method for the exit of a pipe jacking machine head when the receiving well cannot be stopped from settling, characterized in that, Includes the following steps: Step 1: Prepare the steel casing according to the size of the pipe jacking machine head and the depth of the receiving well; Step 2: Backfill the receiving well; the backfill height is less than the height of the steel casing, and the backfill height is 30-50cm less than the height of the steel casing. Step 3: Determine the position of the vertically placed steel casing based on the position of the extension line of the pipe jacking machine head in the receiving well, and place the steel casing. The specific method for placing the steel casing is as follows: start the steel casing hoisting and sinking construction by using an excavator and a crane. The sinking is carried out by using a counterweight plus the excavator to press down. When the frictional resistance is large, the steel casing is excavated to reduce the resistance and slowly vibrated and sunk in conjunction with a vibratory pile driver. Step 4: Use steel sheet piles to isolate the area around the steel caisson; Step 5: Clean the soil from the bottom of the steel casing and the partitions, and seal the bottom. When cleaning the soil from the bottom of the steel casing and the partitions, first clean the soil in areas A, B, C, and D in sequence and seal the bottom. Then clean the soil in areas E, F, and G in sequence and seal the bottom. Finally, clean the soil from the steel casing and seal the bottom. When sealing the bottom of the partitions, areas A, B, C, and D need to be sealed all the way to the top of the steel casing. Step 6: Perform curing treatment on the bottom seal. After curing, clean the inside of the steel casing and reinforce it. Step 7: Drill holes based on the approximate center position of the pipe jacking head obtained from the measurement to confirm the actual position of the pipe jacking head; Step 8: Based on the actual position of the jacking head obtained from the drilling confirmation, enlarge and trim the hole until the face cutterhead of the jacking head is fully exposed in the transverse tunnel of the steel casing. Step 9: Carry out pipe jacking construction until the pipe jacking machine head is completely inserted into the steel casing, and complete the exit of the pipe jacking machine head.

2. The construction method according to claim 1, characterized in that, In step 1, the steel casing is a steel pipe with a wall thickness of not less than 10mm; the diameter of the steel casing is greater than the cross-sectional diameter and length of the pipe jacking machine head; the height of the steel casing is not greater than the depth of the receiving well and not less than half the depth of the receiving well.

3. The construction method according to claim 1, characterized in that, In step 1, a support rod is also installed at the bottom of the steel casing.

4. The construction method according to claim 1, characterized in that, The bottom sealing height surface inside the steel casing is 20 mm above the actual bottom elevation of the machine head. 40cm.

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