Shell abandoning freezing underground excavation method after pipe jacking shutdown

Abstract

The invention provides a shell abandoning freezing underground excavation construction method after pipe jacking shutdown, which comprises the following steps of: 1, stopping a pipe jacking machine when form relieved teeth of the pipe jacking machine are jacked to an isolation pile, and making preparation work for installing a freezing pipe; 2, a freezing pipe is installed between a shell of the pipe jacking machine and the outer wall of the existing building, a freezing wall is formed through positive freezing, and a protective door is installed on a breast plate of the pipe jacking machine; 3, after the frozen wall meets the design requirement, a breast plate is cut off, a profile steel support is installed, and a soil body is manually excavated to the outer wall of the existing building; and 4, after manual underground excavation is completed, the cast-in-place shell discarding cast-in-place section and the manual underground excavation section form a cast-in-place concrete box culvert, after the design strength is achieved, freezing is stopped, freezing holes are blocked, filling and thaw collapse grouting are conducted on the manual underground excavation section, and construction of the manual underground excavation section is completed. The invention relates to the technical field of tunnel pipe-jacking construction, and can solve the problems that in the prior art, pipe-jacking construction encounters barriers such as isolation piles, and a receiving well cannot be arranged in an existing building, so that pipe-jacking tunnel construction is difficult.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel jacking construction, and in particular to a shell abandonment freezing dark excavation method after the jacking machine is shut down. Background Art

[0002] my country's underground space development has developed rapidly in recent decades and has become an important part of urban construction. Due to the accelerated urbanization process and the increasing shortage of ground space resources, the development and utilization of underground space is particularly important, especially in large and megacities. With the advancement of science and technology and the development of construction technology, underground space development has gradually developed in the direction of complexity, depth and large scale. However, the underground space development process also faces many challenges, such as complex geological conditions, dense underground pipelines, and complex construction environment.

[0003] Pipe jacking has significant advantages in the development of underground connecting passages. It has little impact on the ground environment, strong adaptability, can pass through various obstacles, and is suitable for complex geological conditions. Pipe jacking construction is environmentally friendly and energy-saving, reduces dust and noise pollution, and saves land resources. It has a high degree of mechanization, fast construction efficiency, good quality, ensures the straightness and sealing of the connecting passage, has high construction safety, reduces the risk of deep foundation pit operations, and is widely used in urban underground connecting passages and infrastructure construction.

[0004] Since the isolation piles are used to protect the original buildings, but they will hinder the advancement of the pipe jacking machine, when the receiving end is an existing building, it is impossible to set up a receiving well. In the development of underground connecting passages, the pipe jacking project often faces obstacles such as isolation piles and the inability to set up receiving wells in existing buildings, which makes the construction of the pipe jacking tunnel difficult. Therefore, it is necessary to provide a shell-abandoning frozen dark excavation method after the pipe jacking machine is shut down, which can solve the problem in the prior art that the pipe jacking construction encounters obstacles such as isolation piles and the inability to set up receiving wells in existing buildings, which makes the construction of the pipe jacking tunnel difficult. Summary of the invention

[0005] The purpose of the present invention is to provide a method of abandoning the shell and freezing the dark excavation after the jacking machine is shut down, which can solve the problem in the prior art that the jacking construction encounters obstacles such as isolation piles and the receiving well cannot be set in the existing buildings, resulting in difficulties in the jacking tunnel construction.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] A method for abandoned shell freezing and dark excavation after pipe jacking is stopped, comprising the following steps:

[0008] Step 1: When the shovel teeth of the pipe jacking machine reach the isolation pile, the pipe jacking machine stops to prepare for the installation of the freezing pipe;

[0009] Step 2: Install a freezing pipe between the casing of the pipe jacking machine and the exterior wall of the existing building, actively freeze to form a freezing wall, and install a protective door on the chest plate of the pipe jacking machine;

[0010] Step 3: After the frozen wall meets the design requirements, the breast plate is cut off, the steel support is installed, and the soil is manually excavated to the existing building exterior wall;

[0011] Step 4: After the completion of manual underground excavation, the abandoned shell cast-in-place section and the manual underground excavation section are cast in situ to form a cast-in-situ concrete box culvert. After the manual underground excavation section reaches the design strength, the freezing is stopped, the freezing holes are sealed, and the manual underground excavation section is filled and melt-settled by grouting. The construction of the manual underground excavation section is completed.

[0012] The step 1 comprises the following sub-steps:

[0013] Step 1.1: Place the shovel teeth against the isolation pile as the stopping condition of the pipe jacking machine, and perform water sealing after the pipe jacking machine stops;

[0014] Step 1.2: Remove the equipment inside the casing of the pipe jacking machine and seal the holes on the chest plate in time;

[0015] Step 1.3: Mark the construction position of the freezing hole on the shell, and cut off the annular ribs that affect the construction of the freezing hole at the marked position;

[0016] Step 1.4: Add temporary steel supports inside the shell according to the location of the drilling rig during drilling construction.

[0017] The step 2 comprises the following sub-steps:

[0018] Step 2.1: Drill a hole at the freezing hole marked on the shell and install the orifice pipe;

[0019] Step 2.2: Construct freezing holes, which penetrate the shell, isolation piles, cast-in-place piles and cast-in-place retaining piles;

[0020] Step 2.3: Drill a second hole to form a freezing hole, install the freezing pipe on the orifice pipe, and seal the gap between the flange of the orifice pipe and the freezing pipe with a steel plate;

[0021] Step 2.4: Repeat the above steps until all freezing pipes are installed, so that all freezing pipes are arranged circumferentially outside the shell and are inclined between the shell and the existing building exterior wall;

[0022] Step 2.5: Actively freeze the soil between the shell and the existing building exterior wall through the freezing pipe to form a frozen wall;

[0023] Step 2.6: Install protective doors on the chest plate according to the excavation compartment areas of the manual underground excavation.

[0024] In the step 2.6, the excavation compartment area of ​​the manual dark excavation is optimized and adjusted in combination with the jacking cutter head layout diagram, and is divided into eight excavation compartment areas, which are numbered according to the excavation order, namely, the upper left side of the middle part, the lower left side of the middle part, the upper right side of the middle part, the lower right side of the middle part, the upper sides of the edge, and the lower sides of the edge; a protective door is installed above and below.

[0025] The step 3 comprises the following sub-steps:

[0026] Step 3.1: After the frozen wall meets the design requirements, strengthen the local freezing at the junction of the breast plate and the shell, and cut off the breast plate;

[0027] Step 3.2: Use the shell between the breast plate and the edge of the shovel teeth as an annular support to manually remove the residual soil on the head, that is, the soil between the breast plate and the isolation pile. After the slag is cleared, remove the cutter head of the pipe jacking machine;

[0028] Step 3.3: According to the number of each excavation compartment area, the soil is manually excavated to the outer wall of the existing building, and steel supports are set in the excavation compartment area.

[0029] The steel support comprises an annular steel support, a middle support and a support channel steel. Several annular steel supports are arranged between the shell and the outer wall of the existing building at intervals, and the middle support is arranged inside the annular steel support; the support channel steel is arranged on the top of several annular steel supports, and the parts of the isolation piles and cast-in-place piles cut off by the freezing holes are connected to the support channel steel, so that the isolation piles and cast-in-place piles are connected to the steel support as a whole.

[0030] The step 4 comprises the following sub-steps:

[0031] Step 4.1: After the excavation is completed, cast the concrete of the artificial dark excavation section in situ. When the concrete of the artificial dark excavation section reaches the designed strength, remove the steel support and stop freezing;

[0032] Step 4.2: After freezing stops, cut off the orifice pipe and frozen pipe on the shell as soon as possible to prevent the frozen wall around the orifice pipe and frozen pipe from thawing and leaking;

[0033] Step 4.3: The freezing pipes abandoned in the soil should be filled and the freezing holes should be sealed;

[0034] Step 4.4: When all frozen holes are sealed and the concrete strength of the artificial dark excavation section reaches 70%, the first gap between the outer wall of the cast-in-place concrete box culvert and the inner wall of the frozen wall is filled with grouting, and a filling grouting hole is set in each section; the gap between the primary lining and the frozen soil curtain and the gap between the supporting layer and the structural layer of the arch top are filled with thaw-sinking grouting.

[0035] Step 4.5: One month after freezing is stopped, the second gap between the frozen soil and the unfrozen soil of the frozen wall is thaw-sinking grouting, and thaw-sinking grouting holes are drilled continuously at the filling grouting holes, and the thaw-sinking grouting holes penetrate the frozen wall.

[0036] In the step 4.1, when pouring concrete, the joint surface between the existing building exterior wall and the artificial dark excavation section is roughened, treated as a construction joint, two water-swelling waterstop strips are added, grouting holes are reserved around, and waterproofing treatment is performed by grouting through the grouting holes.

[0037] In the step 4.4, a grouting hole is set on the outside of the shovel teeth of the jacking machine, that is, between the abandoned shell cast-in-place section and the artificial dark excavation section, and a metal water stop strip is set. After the secondary structure is cast in the later stage, a water receiving trough is set in the gap between the shell and the concrete of the artificial dark excavation section, and the gap is filled with grouting through the grouting hole.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention uses the contact of the shovel teeth with the isolation piles as the stopping condition of the pipe jacking machine, and adopts the method of freezing soil + manual dark excavation to excavate the soil to the outer wall of the existing building, and removes the isolation piles in the process of excavating the soil, thereby solving the problem in the prior art that the pipe jacking construction encounters obstacles such as isolation piles and the receiving well cannot be set in the existing building, resulting in the difficulty of the pipe jacking tunnel construction. The present invention is suitable for the method of tunnel construction by using the frozen dark excavation construction technology after the pipe jacking is stopped under the conditions of soft soil strata rich in water, the existence of isolation piles in the tunnel resulting in the pipe jacking being unable to continue to advance, and the existing building having no receiving well. The method has guiding significance for similar projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0041] Figure 1 It is a construction schematic diagram of the shell abandonment freezing dark excavation method after the pipe jacking machine is shut down according to the present invention;

[0042] Figure 2 It is a layout diagram of freezing pipes in the shell abandonment freezing dark excavation method after the pipe jacking machine is shut down according to the present invention;

[0043] Figure 3 It is a partial structural schematic diagram of the breast plate and the shovel teeth in the shell abandonment freezing dark excavation method after the jacking machine is stopped according to the present invention;

[0044] Figure 4 It is a cross-sectional view of the frozen wall and the steel support in the shell abandonment freezing dark excavation method after the pipe jacking machine is stopped according to the present invention;

[0045] Figure 5 It is a numbering diagram of the excavation sequence of the compartment area in the shell abandonment freezing dark excavation method after the pipe jacking is stopped according to the present invention;

[0046] Figure 6 It is a schematic diagram of the installation of the protective door in the shell abandonment freezing dark excavation method after the pipe jacking is stopped according to the present invention;

[0047] Figure 7 It is a cross-sectional view of the medium-shaped steel support of the shell abandonment freezing dark excavation method after the pipe jacking machine is stopped in the present invention;

[0048] Figure 8 It is a waterproof construction drawing of the shell abandonment freezing dark excavation method after the pipe jacking machine is shut down according to the present invention;

[0049] Fig. 9 It is a waterproof construction drawing of the artificial dark excavation section and the existing building outer wall in the shell abandonment freezing dark excavation construction method after the jacking machine is stopped in the present invention;

[0050] Fig.10 It is a filling grouting construction drawing in the shell abandonment freezing dark excavation method after the jacking pipe is stopped in the present invention;

[0051] Fig.11 yes Fig.10 Middle AA section;

[0052] Fig.12 It is a construction drawing of melting and sinking grouting in the shell abandonment freezing dark excavation method after the pipe jacking is stopped in the present invention;

[0053] Fig.13 yes Fig.12 Middle BB cross-section.

[0054] In the figure, 1-shell; 2-freezing pipe; 3-chest plate; 4-protective door; 5-shovel teeth; 6-annular steel support; 7-circumferential ribs; 8-isolation piles; 9-cast-in-place piles; 10-freezing wall; 11-supporting channel steel; 12-steel support; 13-grouting holes; 14-metal water stop strips; 15-external building exterior walls; 16-water receiving trough; 17-water-expanding water stop strips; 18-filling grouting holes; 19-thaw-settlement grouting holes; 20-cast-in-place concrete box culvert; 21-unfrozen soil; 22-first gap; 23-second gap. DETAILED DESCRIPTION

[0055] The following is a further detailed description of a method for freezing and dark excavation of abandoned shells after the pipe jacking machine is shut down, in combination with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0056] During the construction of the pipe jacking machine, there is a row of isolation piles 8 on the outside of the existing building outer wall 15 at the pipe jacking receiving end (existing building), which does not meet the conditions for continued jacking, and a receiving well cannot be set up in the existing building. Therefore, the pipe jacking machine stops jacking after it reaches the isolation piles 8, and the pipe jacking machine equipment is dismantled. The section from the isolation piles 8 to the existing building outer wall 15 is constructed using frozen soil + manual excavation. Frozen pipes 2 are arranged between the shell 1 of the pipe jacking machine and the existing building outer wall 15. After a stable frozen wall 10 is formed around the manual excavation section, manual excavation is carried out. After the excavation is completed, concrete is cast in place.

[0057] A method for abandoned shell freezing and dark excavation after pipe jacking is stopped, comprising the following steps:

[0058] Please see attached Figure 1 , Step 1: When the shovel teeth 5 of the pipe jacking machine reach the isolation pile 8, the pipe jacking machine stops and prepares for the installation of the freezing pipe 2.

[0059] The step 1 comprises the following sub-steps:

[0060] Step 1.1: Place the shovel teeth 5 against the isolation piles 8 as a stop condition for the pipe jacking machine. After the pipe jacking machine is stopped, water sealing treatment is performed, that is, grouting reinforcement is performed on the tunnel face to prevent water leakage from the equipment in the shell 1 during the dismantling process, and reduce the risk of settlement or floating of the shell 1 and the prefabricated pipe segment after the pipe jacking machine is stopped.

[0061] Specifically, the water sealing treatment is to perform single-liquid / double-liquid grouting into the soil of the tunnel face to prevent radial water inflow after the removal of the spiral excavator of the pipe jacking machine, the removal of the cutterhead transmission device and the cutting of the breast plate 3.

[0062] Step 1.2: Remove the main bearing, spiral excavator and other equipment in the casing 1 of the pipe jacking machine, and promptly seal the holes on the breast plate 3 by welding steel plates.

[0063] Step 1.3: Mark the construction position of the freezing hole on the shell 1, and cut off the annular ribs 7 that affect the construction of the freezing hole at the marked position.

[0064] Step 1.4: Since the removal of the annular ribs 7 will lead to insufficient local bearing capacity of the shell 1, causing deformation of the shell 1 and settlement of the soil, it is necessary to add temporary steel supports (not shown in the figure) composed of vertical and horizontal steel sections in the shell 1 in combination with the installation position of the drilling rig during drilling construction to meet the bearing capacity and deformation requirements and prevent the shell 1 from being deformed due to soil pressure.

[0065] Step 2: Install the freezing pipe 2 between the casing 1 of the pipe jacking machine and the outer wall 15 of the existing building, actively freeze to form a freezing wall 10, and install a protective door 4 on the breast plate 3 of the pipe jacking machine.

[0066] The step 2 comprises the following sub-steps:

[0067] Step 2.1: Drill a hole at the freezing hole marked on the shell 1 and install an orifice pipe (not shown in the figure).

[0068] Specifically, a hole is opened in the shell 1 at a designed angle using a hole opener (equipped with a diamond drill bit for coring), and the coring drilling is stopped at 100 mm away from the outer wall of the shell 1, and the orifice pipe is installed. The installation method of the orifice pipe is as follows: first, the opening of the hole is chiseled flat, four expansion screws are set at intervals at the hole, and then hemp is wrapped around the fish scale buckle of the orifice pipe, and the orifice pipe is installed after applying sealing material, and tightened with four expansion screws, and then the ball valve and the orifice sealing device are installed.

[0069] Preferably, before the freezing hole is drilled, grouting can be filled into the soil through the reserved grouting holes in the shell 1 to improve the stratum and reduce the risk of freezing hole drilling construction.

[0070] Step 2.2: Construct freezing holes, which penetrate the shell 1 and the isolation pile 8 Cast-in-place piles 9 (850@600) and cast-in-place retaining piles (not shown in the figure, ).

[0071] Specifically, a diamond coring drill bit is used to penetrate the shell 1. After the shell 1 is penetrated, the drill bit is replaced with a composite sheet alloy drill bit for penetrating the soil, isolation piles 8 and cast-in-place piles 9. A drilling rig with high torque is selected for drilling construction.

[0072] If there are obstacles such as steel bars and steel plates at the end of the drilling process, resulting in a long period of no progress, the diamond drill bit should be replaced for core drilling. The final hole position of the freezing hole is the exterior wall of the existing building 15. The drilling depth and deflection angle should be strictly controlled during the drilling process to prevent damage to the existing structure.

[0073] Since the actual stopping position of the pipe jacking machine may differ from the drawing, and the inclination angle of the freezing pipe 2 is fixed, it is necessary to measure the actual distance between the stopping position of the pipe jacking machine and the existing building outer wall 15 after the pipe jacking machine is stopped, so as to determine the opening point and opening distance of the freezing pipe 2.

[0074] Step 2.3: Drill a second hole to form a freezing hole, install the freezing pipe 2 on the orifice pipe, and seal the gap between the flange of the orifice pipe and the freezing pipe 2 with steel plate welding.

[0075] Please see attached Figure 2 Step 2.4: Repeat the above steps until all the freezing pipes 2 are installed, so that all the freezing pipes 2 are arranged circumferentially outside the shell 1 and are tilted between the shell 1 and the existing building outer wall 15.

[0076] Step 2.5: Actively freeze the soil between the shell 1 and the existing building exterior wall 15 through the freezing pipe 2 to form a frozen wall 10, as shown in the attached Figure 1 and attached Figure 4 shown.

[0077] Use brine circulation for active freezing. After the active freezing is completed, analyze the freezing effect. After ensuring the freezing effect, perform exploratory hole construction before excavation to ensure that no pressurized muddy water flows out. If there is external water, extend the active freezing time.

[0078] Preferably, the active freezing stage is the stage of formation of the frozen soil curtain, and the designed freezing time is about 35-40 days; the single hole flow rate of the freezing pipe 2 is required to be not less than 5m3 / h; the brine temperature drops to below -18°C after 7 days of active freezing, and drops to below -24°C after 15 days of active freezing; the brine temperature drops to below -28°C before excavation, and the temperature difference between the return and return circuits is not greater than 2°C. If the brine temperature and brine flow rate do not meet the design requirements, the active freezing time should be extended, and it should also be kept below -28°C during excavation to ensure the freezing effect.

[0079] During the active freezing process, due to the influence of the frost heave effect of the soil, the soil of the artificial dark excavation section will produce a large compressive stress, and the soil outside the artificial dark excavation section will also produce some stress. In order to prevent the soil from being deformed due to excessive stress, causing the upper soil to bulge or settle, causing the upper structure to exceed the normal use limit or even be damaged, it is necessary to set a pressure relief hole (not shown in the figure) on the inside of the frozen wall 10. Specifically, a pressure relief hole is set on the inside of the frozen wall 10, and the pressure relief hole should be deep into the interlayer soil between the two rows of cast-in-place piles 9. The pressure of the frozen soil on the soil layer is released through the pressure relief hole to control the impact of frost heave on the surrounding environment, and the stress level of the peripheral soil is detected in real time. Once it exceeds the normal range, the pressure relief operation is immediately performed.

[0080] The type of frozen wall 10 is Class I frozen wall, which is mainly used to seal the risk of water leakage around during excavation. The calculation model of frozen wall 10 is established, and the plate periphery of frozen wall 10 adopts fixed constraints, without considering the constraint effect of steel support in the initial excavation period, and the displacement value of frozen wall 10 is verified.

[0081] The freezing method has the advantages of high stability, low environmental impact, adaptability to complex conditions and high-precision construction in the construction of connecting channels. Freezing the soil can improve the strength and stability of the surrounding rock and reduce the risk of landslides and deformation; the construction process has little interference with the ground and the surrounding environment, low noise and vibration, and is suitable for densely populated urban areas; it can cope with high groundwater levels and complex geological conditions, ensuring smooth construction in special environments; and it provides a good construction space for high-precision operations and structural quality control.

[0082] Step 2.6: Install the protective door 4 on the breast plate 3 according to the excavation compartment area of ​​the manual dark excavation.

[0083] Preferably, the excavation compartment area of ​​the manual dark excavation can be optimized and adjusted in combination with the layout diagram of the jacking cutter head to determine the specific installation position of the protective door 4. Figure 5 , can be divided into eight excavation compartments, numbered in the order of excavation, namely, the upper left side of the middle ①, the lower left side of the middle ②, the upper right side of the middle ③, the lower right side of the middle ④, the upper sides of the edge ⑤, and the lower sides of the edge ⑥. Install one protective door 4 on the top and bottom, as shown in the attached Figure 6 As shown, an excavation channel is quickly formed, and subsequent manual underground excavation construction can be conveniently passed through the protective door 4.

[0084] Step 3: After the frozen wall 10 meets the design requirements, the breast plate 3 is cut off, the steel support 12 is installed, and the soil is manually excavated to the existing building outer wall 15.

[0085] The step 3 comprises the following sub-steps:

[0086] Step 3.1: After the freezing wall 10 meets the design requirements, strengthen the local freezing at the junction of the breast plate 3 and the shell 1, and cut off the breast plate 3.

[0087] Since hot work is required to remove the breast plate 3 and the shell 1 is a good thermal conductive material, hot work is bound to affect the freezing effect of the soil. Therefore, it is necessary to strengthen the local freezing at the junction of the breast plate 3 and the shell 1. After the hot cutting of the breast plate 3, the excavation time is postponed accordingly, and freezing is continued to eliminate the impact of hot work on the frozen wall 10. A freezing device with a refrigeration capacity far greater than the freezing capacity is selected, and a complete spare freezing device is equipped. During freezing and excavation, the temperature of each branch circuit of the temperature measuring hole and the freezing hole is tested.

[0088] During the hot work of removing the breast plate 3, the soil may undergo a certain freeze-thaw cycle, during which the stress in the soil is unstable. During the hot work, pressure is released through the pressure relief holes to ensure stable stress in the soil.

[0089] Before the freezing hole drilling begins, the surrounding buildings are monitored from the beginning of the drilling period to the end of the melting and grouting. After the hot cutting of the breast plate 3 is completed, the freezing is continued until the temperature of the freezing wall 10 is stable before the next construction operation can be carried out.

[0090] The freezing temperature field of the freezing wall 10 is calculated, the temperature field is analyzed according to the final hole positions of the freezing holes, a finite element analysis model of the temperature field is established, the thickness of the freezing wall 10 and the average temperature of the freezing wall 10 are verified, and the arrangement of the freezing holes is verified.

[0091] Step 3.2: Using the shell 1 between the breast plate 3 and the edge of the shovel teeth 5 as an annular support, the operator manually removes the residual soil from the head, that is, the soil between the breast plate 3 and the isolation pile 8. After the slag is cleared, the cutter head of the pipe jacking machine is removed.

[0092] Step 3.3: According to the number of each excavation compartment area, the soil is manually excavated to the existing building outer wall 15, and steel support 12 is set in the excavation compartment area, as shown in the attached Figure 4 and attached Figure 5 shown.

[0093] The order of manual excavation is from inside to outside and from top to bottom. After one excavation compartment area is dug through, the next excavation compartment area is excavated. During the excavation process, the isolation piles 8 and cast-in-place piles 9 at the corresponding positions are broken simultaneously.

[0094] Please see attached Figure 7 The steel support 12 includes an annular steel support 6, a middle support and a support channel steel 11. Several annular steel supports 6 are arranged between the shell 1 and the existing building outer wall 15 at intervals, and the middle support is arranged in the annular steel support 6; the support channel steel 11 is arranged on the top of several annular steel supports 6, and the parts of the isolation piles 8 and the cast-in-place piles 9 cut off by the freezing holes are connected to the support channel steel 11, so that the isolation piles 8 and the cast-in-place piles 9 are connected to the steel support 12 as a whole.

[0095] The steel support 12 can provide sufficient bearing capacity, and bear the load of the upper pile body at the cutoff of the isolation pile 8 and the cast-in-place pile 9 through the support channel steel 11 and the annular steel support 6, thereby preventing the upper pile body and the existing building outer wall 15 from sinking and causing the upper soil to settle and deform. The annular steel support 6 is set circumferentially along the upper, lower, left and right edges of the excavated compartment area to bear the soil pressure around it, prevent soil deformation and settlement during excavation, and ensure the safety of manual dark excavation construction.

[0096] The middle support can be made of HW250×250 steel brackets, and the spacing between the steel brackets is 0.8m. In order to increase the stability of the steel brackets, the adjacent rows of steel brackets are connected to each other by steel bar welding.

[0097] During the excavation process, the installation position of the steel support 12 can be fine-tuned to ensure that the steel support 12 is located below the cutoff of the isolation pile 8 and the cast-in-place pile 9. The steel bars at the cutoff of the isolation pile 8 and the cast-in-place pile 9 are all welded to the support channel steel 11 and the annular steel support 6, so that the isolation pile 8 and the cast-in-place pile 9 are connected to the steel support 12 as a whole. Preferably, an annular steel support 6 is arranged every 800 mm in the forward excavation, the isolation pile 8 is located on the first annular steel support 6, and the cast-in-place pile 9 is on the last two annular steel supports 6.

[0098] Step 4: After the completion of artificial dark excavation, cast the artificial dark excavation section in situ. After the artificial dark excavation section reaches the designed strength, stop freezing, seal the freezing holes, fill and melt-sink grouting the artificial dark excavation section, and the construction of the artificial dark excavation section is completed.

[0099] The step 4 comprises the following sub-steps:

[0100] Step 4.1: After the excavation is completed, concrete of the abandoned shell cast-in-place section and the artificial dark excavation section is cast in situ to form a cast-in-situ concrete box culvert 20. After the concrete of the artificial dark excavation section reaches the design strength, the steel support 12 is removed and the freezing is stopped.

[0101] When the freezing pipe 2 does not freeze, the temperature of the frozen brine at the pouring location is properly controlled during the concrete pouring process of the artificial underground excavation section to avoid the negative impact of too low a temperature of the frozen brine on the pouring quality of the concrete.

[0102] Please see attached Fig. 9 When pouring concrete, the joint surface between the existing building exterior wall 15 and the artificial dark excavation section is roughened and treated as a construction joint. Two water-swelling waterstop strips 17 are added, and grouting holes 13 are reserved around. Grouting is performed through the grouting holes 13 for waterproofing to prevent water leakage in the later stage.

[0103] Due to the small construction space of the channel, the concrete of the channel top plate cannot be effectively vibrated, which affects the quality of the concrete and further affects the waterproof ability of the top plate. Therefore, self-compacting concrete can be used as the concrete of the channel top plate, and attached vibrating equipment can be used to strengthen the concrete vibration; when the steel bars of the cut-off pile pass through the supporting channel steel 11 of the steel support 12, a water stop steel plate is installed, and when the concrete strength of the artificial dark excavation section meets the requirements, the steel support 12 is cut off.

[0104] Step 4.2: After freezing stops, the orifice pipe and the frozen pipe 2 on the shell 1 should be cut off as soon as possible to prevent the frozen wall 10 around the orifice pipe and the frozen pipe 2 from thawing and leaking.

[0105] Step 4.3: The freezing pipe 2 abandoned in the soil should be filled to seal the freezing hole.

[0106] Preferably, compressed air is used to blow dry the salt water in the freezing pipe 2 before filling it, and the material for filling the freezing pipe 2 should be cement mortar of M10 or above or concrete of C20 or above. For the freezing pipe 2 with an upward elevation angle, the length of the filling pipe should be no less than 1.5m within the mouth of the freezing pipe 2. For the freezing pipe 2 with a downward depression angle, in principle, the entire section of the orifice pipe cut-off part should be filled, and a 10m thick steel plate should be used for welding and sealing, with a weld height of 6mm, and water-expanding waterproofing glue should be applied, and then C30 sulphoaluminate micro-expansive concrete should be used to fill the remaining space.

[0107] Please see attached Fig.10 and attached Fig.11Step 4.4: When all the freezing holes are sealed and the concrete strength of the artificial dark excavation section reaches 70%, the first gap 22 between the outer wall of the cast-in-place concrete box culvert 20 and the inner wall of the freezing wall 10 is filled with grouting, and 16 filling and grouting holes 18 are set in each section.

[0108] Grouting to fill the first gap 22 may be performed using a conventional grouting process, which will not be described in detail herein.

[0109] Please see attached Fig.12 and attached Fig.13 Step 4.5: Since the soil of the frozen wall 10 will shrink to a certain extent when it thaws naturally, a second gap 23 will be generated between the frozen soil of the frozen wall 10 and the unfrozen soil 21. Therefore, after stopping freezing for one month, the second gap 23 is melt-sinking grouting, and the melting and sinking grouting hole 19 is drilled at the filling grouting hole 18. The depth of the melting and sinking grouting hole 19 is preferably enough to just penetrate the frozen wall 10.

[0110] The melting and settling grouting can track and grout the frozen soil of the frozen wall 10 during its natural melting process, thereby preventing the ground from settling. The end of the melting and settling grouting is based on the stability of the ground deformation. Preferably, if the ground settlement is kept within 0.5 mm every half a month for a consecutive month, the melting and settling grouting can be ended, and the melting and settling grouting hole 19 is then blocked.

[0111] The grouting process of the melt-sinking grouting holes 19 and the sealing of the melt-sinking grouting holes 19 can be carried out by conventional grouting technology, which will not be described in detail here.

[0112] Since there is a through gap between the shell 1 and the cast-in-place concrete box culvert 20, in order to prevent groundwater from flowing into the gap during subsequent use, please refer to the attached Figure 8 A grouting hole 13 is set on the outside of the shovel tooth 5 of the jacking machine, that is, between the abandoned shell cast-in-place section and the artificial dark excavation section, and a metal water stop strip 14 is set. After the secondary structure is cast in the later stage, a water receiving trough 16 is set at this joint so that grouting can be injected through the grouting hole 13 at any time to fill the gap.

[0113] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for freezing and dark excavation of abandoned shells after pipe jacking is stopped, characterized in that: The following steps are involved: Step 1: When the shovel teeth (5) of the pipe jacking machine reach the isolation pile (8), the pipe jacking machine stops to prepare for installing the freezing pipe (2); Step 2: installing a freezing pipe (2) between the casing (1) of the pipe jacking machine and the outer wall (15) of the existing building, actively freezing to form a freezing wall (10), and installing a protective door (4) on the chest plate (3) of the pipe jacking machine; Step 3: After the frozen wall (10) meets the design requirements, the breast plate (3) is cut off, the steel support (12) is installed, and the soil is manually excavated to the existing building outer wall (15); Step 4: After the completion of the artificial dark excavation, the abandoned shell cast-in-place section and the artificial dark excavation section are cast in situ to form a cast-in-situ concrete box culvert (20). After the artificial dark excavation section reaches the designed strength, the freezing is stopped, the freezing holes are blocked, and the artificial dark excavation section is filled and melt-settled and grouted. The construction of the artificial dark excavation section is completed.

2. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 1, characterized in that: The step 1 comprises the following sub-steps: Step 1.1: placing the shovel teeth (5) against the isolation piles (8) as a stop condition for the pipe jacking machine, and performing water sealing after the pipe jacking machine is stopped; Step 1.2: Remove the equipment in the casing (1) of the pipe jacking machine and promptly seal the holes on the breast plate (3); Step 1.3: marking the freezing hole construction position on the shell (1), and cutting off the annular ribs (7) at the marked position that affect the freezing hole construction; Step 1.4: Add temporary steel supports inside the housing (1) in accordance with the location where the drilling rig is installed during drilling construction.

3. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 1, characterized in that: The step 2 comprises the following sub-steps: Step 2.1: Drill a hole at the freezing hole marked on the shell (1) and install the orifice pipe; Step 2.2: constructing a freezing hole, wherein the freezing hole penetrates the shell (1), the isolation pile (8), the cast-in-place pile (9) and the cast-in-place retaining pile; Step 2.3: drilling a second time to form a freezing hole, installing the freezing pipe (2) on the orifice pipe, and sealing the gap between the flange of the orifice pipe and the freezing pipe (2) by welding with a steel plate; Step 2.4: Repeat the above steps until all the freezing pipes (2) are installed, so that all the freezing pipes (2) are arranged circumferentially outside the shell (1) and are obliquely located between the shell (1) and the existing building outer wall (15); Step 2.5: Actively freeze the soil between the shell (1) and the existing building outer wall (15) through the freezing pipe (2) to form a frozen wall (10); Step 2.6: Install a protective door (4) on the breast plate (3) according to the excavation compartment area of ​​the manual dark excavation.

4. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 3, characterized in that: In the step 2.6, the excavation compartment area of ​​the manual dark excavation is optimized and adjusted in combination with the layout diagram of the jacking cutter head, and is divided into eight excavation compartment areas, which are numbered according to the excavation sequence, namely, the upper left side of the middle, the lower left side of the middle, the upper right side of the middle, the lower right side of the middle, the upper sides of the edge, and the lower sides of the edge; and a protective door (4) is installed at the top and bottom.

5. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 1, characterized in that: The step 3 comprises the following sub-steps: Step 3.1: After the freezing wall (10) meets the design requirements, the local freezing of the junction between the breast plate (3) and the shell (1) is strengthened, and the breast plate (3) is cut off; Step 3.2: Using the housing (1) between the breast plate (3) and the edge of the shovel teeth (5) as an annular support, manually remove the residual soil at the machine head, that is, the soil between the breast plate (3) and the isolation pile (8). After the slag is removed, the cutter head of the pipe jacking machine is removed; Step 3.3: According to the number of each excavation compartment area, the soil is manually excavated in sequence to the outer wall of the existing building (15), and steel support (12) is set in the excavation compartment area.

6. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 5, characterized in that: The steel support (12) comprises an annular steel support (6), a middle support and a support channel steel (11); a plurality of annular steel supports (6) are arranged at intervals between the shell (1) and the existing building outer wall (15); the middle support is arranged inside the annular steel support (6); the support channel steel (11) is arranged on the top of the plurality of annular steel supports (6); and the portions of the isolation piles (8) and the cast-in-place piles (9) cut off by the freezing holes are connected to the support channel steel (11), so that the isolation piles (8) and the cast-in-place piles (9) are connected to the steel support (12) as a whole.

7. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 1, characterized in that: The step 4 comprises the following sub-steps: Step 4.1: After excavation is completed, concrete is poured in the artificial dark excavation section. After the concrete in the artificial dark excavation section reaches the designed strength, the steel support (12) is removed and freezing is stopped; Step 4.2: After freezing stops, the orifice pipe and the frozen pipe (2) on the shell (1) are cut off as soon as possible to prevent the frozen wall (10) around the orifice pipe and the frozen pipe (2) from thawing and leaking; Step 4.3: The freezing pipe (2) abandoned in the soil should be filled to seal the freezing hole; Step 4.4: When all the freezing holes are sealed and the concrete strength of the artificial dark excavation section reaches 70%, the first gap (22) between the outer wall of the cast-in-place concrete box culvert (20) and the inner wall of the freezing wall (10) is filled with grouting, and each section is provided with (16) filling and grouting holes (18); Step 4.5: One month after freezing is stopped, the second gap (23) generated between the frozen soil and the unfrozen soil (21) of the frozen wall (10) is subjected to thaw grouting, and thaw grouting holes (19) are drilled further at the filling grouting holes (18), and the thaw grouting holes (19) penetrate the frozen wall (10).

8. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 7, characterized in that: In the step 4.1, when pouring concrete, the joint surface between the existing building outer wall (15) and the artificial dark excavation section is roughened, treated as a construction joint, two water-swelling water stop strips (17) are added, grouting holes (13) are reserved around, and grouting is performed through the grouting holes (13) to perform waterproofing.

9. The method for abandoned shell freezing and dark excavation after pipe jacking is stopped as claimed in claim 7, characterized in that: In the step 4.4, a grouting hole (13) is provided on the outside of the shovel teeth (5) of the pipe jacking machine, i.e., between the abandoned shell cast-in-place section and the artificial dark excavation section, and a metal water stop strip (14) is provided. After the secondary structure is cast in the later stage, a water receiving trough (16) is provided in the gap between the shell (1) and the concrete of the artificial dark excavation section, and the gap is filled with grouting through the grouting hole (13).

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