Construction method of water-rich round gravel layer foundation pit

Abstract

The invention provides a construction method of a water-rich round gravel layer foundation pit, and belongs to the technical field of foundation pit construction. The method comprises the steps that the construction area of the foundation pit is determined; determining a supporting structure of the construction area; earthwork is excavated in a layering, segmenting and blocking mode based on the space-time effect so as to excavate a foundation pit, and the water level change amplitude outside the pit is controlled; setting a plurality of monitoring points in the construction area; the lateral displacement of the retaining wall, the horizontal displacement of a soil body, the ground surface settlement behind the retaining wall, the underground water level outside the foundation pit and the inner supporting axial force in the construction process are obtained through the multiple monitoring points; judging whether the deviation degree between any one parameter of retaining wall lateral displacement, soil mass horizontal displacement, earth surface settlement behind the retaining wall, the underground water level outside the foundation pit and the inner supporting axial force and the preset threshold value of the any one parameter is greater than the preset threshold value or not, if yes, adjusting through preset measures, and if not, adjusting the deviation degree to be greater than the preset threshold value. And data obtained through the multiple monitoring points in the construction process is re-executed, and the difficulty that foundation pit construction meets the preset requirement is lowered.

Description

Technical Field

[0001] The present application relates to the technical field of foundation pit construction, and in particular to a construction method for a foundation pit in a water-rich gravel layer. Background Art

[0002] The construction of foundation pits in water-rich gravel layers is difficult due to their complex geological environment.

[0003] Current methods for constructing foundation pits in water-rich gravel layers involve identifying the construction area and obtaining construction parameters from historical construction processes in similar areas. Construction is then conducted based on these historical construction parameters. After construction is complete, the pit parameters are measured to ensure that the construction meets requirements.

[0004] However, the matching degree of the construction parameters of the above method is poor, which makes it difficult for the foundation pit construction to meet the preset requirements.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0006] The present invention provides a method for constructing a foundation pit in a water-rich gravel layer, which can solve the problem in related technologies that the construction of foundation pits is difficult to meet the preset requirements. The technical solution is as follows:

[0007] According to one aspect of the present application, a method for constructing a foundation pit in a water-rich gravel layer is provided, which is used for a foundation pit in a two-way four-lane highway tunnel project, and the method comprises:

[0008] Determining a construction area of the foundation pit, wherein the construction area includes a first construction section, a second construction section, and a third construction section;

[0009] Determine the support structure of the construction area, the support structure of the first construction section and the third construction section is a composite retaining wall of bored cast-in-place piles and high-pressure rotary jet pile water-stop curtains, the support structure of the second construction section is a retaining wall of interlocking piles, and the support structure in the foundation pit is concrete supports and steel supports;

[0010] Excavate the foundation pit by excavating the earth in layers, sections and blocks based on time and space effects;

[0011] Setting up a plurality of monitoring points in the construction area;

[0012] Obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the axial force of the internal support during the construction process through the multiple monitoring points;

[0013] Determining whether any one of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force deviates from a preset threshold of the any one parameter by a degree greater than a preset threshold;

[0014] When existing, adjustments are made through preset measures, and the steps of obtaining the lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the internal support during the construction process through the multiple monitoring points are re-executed, and the preset measures include reinforcing the support structure, adjusting the excavation depth, excavation order and layering parameters and at least one of grouting.

[0015] Optionally, when it does not exist, the step of obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the internal support during the construction process through the multiple monitoring points is performed.

[0016] Optionally, the plurality of monitoring points are set in the construction area, including:

[0017] 28 first inclinometer points are arranged in the foundation pit to monitor the lateral displacement of the retaining wall, and 28 second inclinometer points are arranged in the deep soil of the foundation pit to monitor the horizontal position of the soil, wherein the deep soil is the soil below 5 meters underground;

[0018] 56 surface settlement monitoring sections behind the wall are arranged at intervals of 10 meters along the perimeter of the foundation pit, with 5 settlement monitoring points set at each section, and the spacing between the settlement monitoring points among the 5 settlement monitoring points is 2 meters, 3 meters, 5 meters, 5 meters and 8 meters respectively;

[0019] 28 groundwater level monitoring points outside the pit are arranged at intervals of 30 meters along the perimeter of the foundation pit;

[0020] Seven internal support horizontal axial force detection sections are set in the foundation pit.

[0021] Optionally, in the construction area, the design speed of the two-way four-lane highway tunnel is 60 kilometers per hour, the full length of the two-way four-lane highway tunnel is 510 meters, the open section of the two-way four-lane highway tunnel is 305 meters, and the buried section is 205 meters. The two-way four-lane highway tunnel is constructed using the open-cut method, the excavation width of the foundation pit ranges from 20.4 meters to 30.8 meters, and the depth of the foundation pit ranges from 1.8 meters to 11.6 meters. The strata in the construction area include backfill soil, silty clay, gravel, pebbles, strongly weathered mudstone and moderately weathered mudstone from top to bottom. The groundwater in the construction area is pore groundwater, and the groundwater level is in the range of 1 meter to 6.2 meters below the surface. The annual variation of the groundwater level is 2 meters.

[0022] Optionally, the first construction section includes a section from 92 meters to 260 meters of the highway tunnel, the second construction section includes a section from 261 meters to 402 meters of the highway tunnel, and the third construction section includes a section from 403 meters to 507 meters of the highway tunnel;

[0023] In the first construction section, the excavation depth ranges from 1.8 meters to 8 meters, the pile lengths of the multiple bored piles and high-pressure rotary jet piles in the first construction section range from 6 meters to 10.5 meters, and the diameter of each bored pile is 800 mm, the center distance between adjacent bored piles in the multiple bored piles is 1000 mm, the diameter of each high-pressure rotary jet pile is 600 mm, the center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes a steel pipe, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

[0024] Optionally, in the second construction section, the excavation depth ranges from 8 meters to 11.6 meters, the interlocking pile retaining wall includes a plurality of interlocking piles, the diameter of the interlocking piles is 1000 mm, the pile length of the interlocking piles ranges from 11 meters to 13.5 meters, the center distance between two adjacent interlocking piles in the plurality of interlocking piles is 750 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes 2 or 3 steel pipes, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

[0025] Optionally, in the third construction section, the excavation depth ranges from 2.5 meters to 8 meters, the pile length of the multiple bored piles and high-pressure rotary jet piles in the third construction section ranges from 9.5 meters to 10 meters, and the diameter of each bored pile is 800 mm, the center distance between adjacent bored piles in the multiple bored piles is 1000 mm, the diameter of each high-pressure rotary jet pile is 600 mm, the center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes a steel pipe, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

[0026] Optionally, obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the axial force of the internal support during the construction process through the multiple monitoring points includes:

[0027] Acquiring lateral displacement data of the retaining wall measured at a plurality of the first inclinometer points;

[0028] Determining data of a maximum lateral displacement section based on the lateral displacement data of the retaining wall, wherein the maximum lateral displacement section is a section in which the lateral displacement of the retaining wall is greater than a first lateral position threshold, and the data of the maximum lateral displacement section includes lateral displacement values of the retaining wall at a plurality of first inclination measurement points arranged along a depth direction of the foundation pit;

[0029] The determining whether the deviation of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force from a preset threshold value of any one of the parameters is greater than a preset threshold value includes:

[0030] Determine whether the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold, the preset lateral displacement data including a preset lateral displacement value composed of the lateral displacement values of the retaining wall of multiple first inclination measuring points arranged along the depth direction of the foundation pit. When the deviation is greater than, determine that the lateral displacement of the retaining wall is greater than the preset threshold value of the lateral displacement of the retaining wall; when the deviation is not greater than, determine that the lateral displacement of the retaining wall is not greater than the preset threshold value of the lateral displacement of the retaining wall.

[0031] Optionally, determining whether a deviation between the lateral displacement data of the maximum lateral displacement section and preset lateral displacement data is greater than a preset lateral displacement deviation threshold comprises:

[0032] obtaining a lateral displacement curve of the maximum lateral displacement section based on the lateral displacement data of the maximum lateral displacement section, wherein the lateral displacement curve of the maximum lateral displacement section includes a curve formed by a plurality of lateral position values included in the lateral displacement data of the maximum lateral displacement section;

[0033] obtaining a lateral displacement curve of the preset lateral displacement data based on the preset lateral displacement data, wherein the lateral displacement curve of the preset lateral displacement data includes a curve formed by a plurality of preset lateral position values included in the preset lateral displacement data;

[0034] determining a first fitting ratio between a lateral displacement curve of the maximum lateral displacement section and a lateral displacement curve of the preset lateral displacement data;

[0035] When the first fitting rate is greater than a first fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and preset lateral displacement data is greater than a preset lateral displacement deviation threshold;

[0036] When the fitting rate is less than or equal to the first fitting rate threshold, it is determined that the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than the preset lateral displacement deviation threshold.

[0037] Optionally, obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the axial force of the internal support during the construction process through the multiple monitoring points includes:

[0038] Acquire soil horizontal displacement data measured by a plurality of the second inclinometer points;

[0039] Determining soil horizontal displacement data of a maximum soil horizontal displacement section based on the soil horizontal displacement data, wherein the maximum soil horizontal displacement section is a section in which the soil horizontal displacement is greater than a first soil horizontal displacement threshold, and the soil horizontal displacement data of the maximum soil horizontal displacement section includes soil horizontal displacement values of a plurality of second inclinometer points arranged along a depth direction of the foundation pit;

[0040] The determining whether the deviation of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force from a preset threshold value of any one of the parameters is greater than a preset threshold value includes:

[0041] Determine whether the deviation between the soil horizontal displacement data of the maximum soil horizontal displacement section and the horizontal displacement data of the preset soil is greater than the preset horizontal displacement deviation, the preset soil horizontal displacement data including the preset soil horizontal displacement value composed of the soil horizontal displacement values of a plurality of second inclinometer points arranged along the depth direction of the foundation pit; if the deviation is greater than, determine that the soil horizontal displacement is greater than the preset threshold value of the soil horizontal displacement; if the deviation is not greater than, determine that the soil horizontal displacement is not greater than the preset threshold value of the soil horizontal displacement.

[0042] Optionally, determining whether a deviation between the soil horizontal displacement data of the maximum soil horizontal displacement section and the preset soil horizontal displacement data is greater than a preset horizontal displacement deviation includes:

[0043] obtaining a soil horizontal displacement curve of the maximum soil horizontal displacement section based on the soil horizontal displacement data of the maximum soil horizontal displacement section, wherein the soil horizontal displacement curve of the maximum soil horizontal displacement section includes a curve formed by a plurality of soil horizontal displacements included in the soil horizontal displacement data of the maximum soil horizontal displacement section;

[0044] obtaining a soil horizontal displacement curve of the horizontal displacement data of the preset soil body based on the horizontal displacement data of the preset soil body, wherein the soil horizontal displacement curve of the horizontal displacement data of the preset soil body includes a curve composed of a plurality of preset soil horizontal displacement values included in the horizontal displacement data of the preset soil body;

[0045] Determining a second fitting ratio between a soil horizontal displacement curve of the maximum soil horizontal displacement section and a soil horizontal displacement curve of the preset soil horizontal displacement data;

[0046] When the second fitting rate is greater than a second fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and preset lateral displacement data is greater than a preset lateral displacement deviation threshold;

[0047] When the second fitting rate is less than or equal to the second fitting rate threshold, it is determined that the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than the preset lateral displacement deviation threshold.

[0048] The beneficial effects of the technical solutions provided in the embodiments of the present application include at least:

[0049] By setting up multiple monitoring points in the construction area and obtaining the lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the inner support in real time during the construction process through these monitoring points, it is determined whether there is a deviation of any parameter of the lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the inner support from the preset threshold of any parameter greater than the preset threshold; when it exists, it can be adjusted through at least one preset measure including strengthening the support structure, adjusting the excavation depth, excavation order and layering parameters and grouting, and re-execute the steps of obtaining the lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the inner support during the construction process through multiple monitoring points. In this way, the construction process of the foundation pit can be monitored in real time, and intervention and adjustment can be made in real time, so that the foundation pit is more likely to meet the preset requirements. This method can be applied to the construction process of various water-rich gravel layer foundation pits and reduces the difficulty of the foundation pit construction meeting the preset requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0051] Figure 1 This is a method flow chart of a construction method for a water-rich gravel layer foundation pit provided by an embodiment of the present application;

[0052] Figure 2 This is a flow chart of another method for constructing a foundation pit in a water-rich gravel layer provided by an embodiment of the present application;

[0053] Figure 3This is a layout diagram of foundation pit monitoring points provided in an embodiment of the present application;

[0054] Figure 4 This embodiment of the present application provides Figure 3 The lateral displacement curve of the pile retaining wall is formed by the lateral displacement data of the retaining wall measured at the first 6 inclination measurement points;

[0055] Figure 5 This embodiment of the present application provides Figure 3 The horizontal displacement curve of deep soil formed by the soil horizontal displacement data measured at the 6 second inclination measurement points;

[0056] Figure 6 This embodiment of the present application provides Figure 3 The surface settlement data behind the two retaining walls form a curve of surface settlement behind the retaining wall over time.

[0057] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0058] In order to make the objectives, technical solutions and advantages of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0059] Figure 1 This is a flow chart of a method for constructing a water-rich gravel foundation pit provided by an embodiment of the present application, which is used for a foundation pit in a two-way four-lane highway tunnel project. The method includes the following steps:

[0060] Step 101: Determine a construction area of a foundation pit, where the construction area includes a first construction section, a second construction section, and a third construction section.

[0061] Step 102: Determine the support structure of the construction area. The support structures of the first and third construction sections are bored cast-in-place piles and high-pressure rotary jet pile water-stop curtain combined retaining walls. The support structure of the second construction section is an interlocking pile retaining wall. The support structure in the foundation pit is concrete support and steel support.

[0062] Step 103: Excavate the foundation pit in layers, sections, and blocks based on temporal and spatial effects. During excavation, longitudinal slopes are cut, and deep wells are used to drain the pit to keep the water level within the pit less than or equal to 1 meter. Furthermore, the fluctuation of the water level outside the pit is controlled. If the fluctuation exceeds a threshold, measures are taken to ensure the safety of the surrounding environment. The foundation pit is excavated to the bottom, and during the construction of the base plate, drainage holes are installed at the well points.

[0063] Step 104: Set up multiple monitoring points in the construction area.

[0064] Step 105: Obtain the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the internal support axial force during the construction process through multiple monitoring points.

[0065] Step 106: Determine whether any one of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force deviates from a preset threshold of any one of the parameters by a degree greater than a preset threshold.

[0066] Step 107: make adjustments through preset measures if any, and re-execute step 105, wherein the preset measures include at least one of reinforcing the support structure, adjusting the excavation depth, the excavation sequence, the layering parameters, and grouting.

[0067] If not present, execute step 105.

[0068] In summary, the construction method of the water-rich gravel layer foundation pit provided by the embodiment of the present application sets up multiple monitoring points in the construction area, and obtains the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the inner support in real time during the construction process through these monitoring points, and judges whether there is a deviation of any one of the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the inner support from the preset threshold of any one of the parameters greater than the preset threshold; when it exists, it can be judged by including reinforcing the support structure The structure is adjusted, the excavation depth, the excavation order and the layering parameters are adjusted, and at least one preset measure in the grouting is adjusted, and the steps of obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the internal support during the construction process are re-executed through multiple monitoring points. In this way, the construction process of the foundation pit can be monitored in real time, and intervention adjustments can be made in real time, making it easier for the foundation pit to meet the preset requirements. This method can be applied to the construction process of various water-rich gravel layer foundation pits, and reduces the difficulty of the foundation pit construction meeting the preset requirements.

[0069] Figure 2 This is a flow chart of another method for constructing a water-rich gravel foundation pit provided by an embodiment of the present application, which is used for a foundation pit in a two-way four-lane highway tunnel project. The method includes the following steps:

[0070] Step 201: Determine a construction area of a foundation pit, where the construction area includes a first construction section, a second construction section, and a third construction section.

[0071] In an exemplary embodiment, in the construction area, the design speed of a two-way four-lane highway tunnel is 60 kilometers per hour, the total length of the two-way four-lane highway tunnel is 510 meters, the open section of the two-way four-lane highway tunnel is 305 meters, and the buried section is 205 meters, wherein the buried section refers to the portion where the main structure of the tunnel is completely covered by the covering soil above. The two-way four-lane highway tunnel is constructed using the open-cut method. The excavation width of the foundation pit ranges from 20.4 meters to 30.8 meters, and the depth of the foundation pit ranges from 1.8 meters to 11.6 meters. The strata in the construction area include fill soil, silty clay, rounded gravel, pebbles, strongly weathered mudstone and moderately weathered mudstone from top to bottom. The groundwater in the construction area is pore water, and the groundwater level is within the range of 1 meter to 6.2 meters below the surface. The annual variation of the groundwater level is 2 meters. Among them, the open-cut method is a construction method in which after excavating the foundation pit in the open air, the construction is carried out sequentially from the bottom to the top (bottom plate casting - side wall casting - top plate casting - waterproof layer construction), and then backfilling and covering with soil.

[0072] The foundation pit involved in the embodiments of the present application may be an open-cut tunnel foundation pit, which is a pit of earth and rock excavated on the ground during tunnel construction using the open-cut method. The open-cut tunnel foundation pit is the working area for open-cut tunnel construction.

[0073] In an exemplary embodiment, the first construction section includes the 92nd to 260th meter section of the highway tunnel, the second construction section includes the 261st to 402nd meter section of the highway tunnel, and the third construction section includes the 403rd to 507th meter section of the highway tunnel.

[0074] In the first construction section, the excavation depth ranges from 1.8 meters to 8 meters, the pile lengths of the multiple bored piles and high-pressure rotary jet piles in the first construction section range from 6 meters to 10.5 meters, and the diameter of each bored pile is 800 mm. The center distance between adjacent bored piles in the multiple bored piles is 1000 mm. The diameter of each high-pressure rotary jet pile is 600 mm. The center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm. The concrete support includes a C30 concrete block with a length and width of 0.8 meters. The steel support includes a steel pipe with a diameter of 609 mm and a wall thickness of 16 mm.

[0075] In the second construction section, the excavation depth ranges from 8 meters to 11.6 meters. The interlocking pile retaining wall includes multiple interlocking piles with a diameter of 1,000 mm and a pile length ranging from 11 meters to 13.5 meters. The center distance between two adjacent interlocking piles in the multiple interlocking piles is 750 mm. The concrete support includes a C30 concrete block with a length and width of 0.8 meters. The steel support includes 2 or 3 steel pipes with a diameter of 609 mm and a wall thickness of 16 mm.

[0076] Optionally, in the third construction section, the excavation depth ranges from 2.5 meters to 8 meters, the pile length of the multiple bored cast-in-place piles and high-pressure rotary jet piles in the third construction section ranges from 9.5 meters to 10 meters, and the diameter of each bored cast-in-place pile is 800 mm, the center distance between adjacent bored cast-in-place piles in the multiple bored cast-in-place piles is 1000 mm, the diameter of each high-pressure rotary jet pile is 600 mm, the center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes a steel pipe, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

[0077] Step 202: Determine the support structure for the construction area. The support structures for the first and third construction sections are bored cast-in-place piles and a high-pressure jet grouting water-stop curtain retaining wall. The support structure for the second construction section is a snap-fit pile retaining wall. The support structure within the foundation pit is concrete supports and steel supports. The high-pressure jet grouting water-stop curtain retaining wall is a combination retaining wall consisting of high-pressure jet grouting piles and a water-stop curtain. The high pressure of the high-pressure jet grouting piles can refer to a pressure range of 20 MPa to 50 MPa.

[0078] In one exemplary embodiment, bored cast-in-place piles are used as vertical flexural retaining structures to resist lateral earth pressure in the foundation pit. High-pressure jet grouting piles are used to fill gaps between piles, forming a continuous water-stopping curtain that blocks groundwater infiltration. Interlocking pile retaining walls alternately interlock reinforced concrete piles (A piles) with plain concrete piles (B piles) to form a continuous wall with both retaining and water-stopping functions. Concrete supports, also known as concrete supports, are rigid internal support structures used in foundation pit projects to horizontally connect support piles / walls and form a spatially stable framework. Steel supports are typically used in combination with concrete supports to provide flexible support.

[0079] Step 203: Excavate the foundation pit in layers, sections, and blocks based on the time-space effect. During excavation, slope the foundation pit longitudinally and use deep wells and pipe wells to drain and lower water levels in the foundation pit so that the water level in the foundation pit is less than or equal to 1 meter.

[0080] Based on the time-space effect, the excavation of earth in layers, sections and blocks to excavate the foundation pit can minimize the deformation of the foundation pit and the surrounding settlement by controlling the unsupported exposure time of the soil (exposure time) and reducing the scope and depth of a single excavation (spatial scale). The stratification is based on the layer height of the support system, so as to control the vertical direction of the excavated foundation pit. The segmentation is based on the length of the foundation pit, the support spacing, and the deformation-sensitive area to control the horizontal direction of the excavated foundation pit. The single-section foundation pit is divided into smaller units by blocks, and the excavated foundation pit is controlled in a planar grid. In the embodiment of the present application, based on the time-space effect, the excavation of earth in layers, sections and blocks to excavate the foundation pit can achieve the effect of significantly reducing the risk of deformation and avoiding catastrophic accidents through fine cutting in the time and space dimensions.

[0081] Step 204: Control the water level fluctuation outside the pit. If any abnormality occurs, take timely measures to ensure the safety of the surrounding environment. Excavate the foundation pit to the bottom of the pit. When constructing the bottom plate, set drainage holes at the well point.

[0082] By controlling the water level outside the pit and setting drainage holes on the bottom plate, the stability of the foundation pit and the safety of the surrounding environment can be guaranteed. For example, the water level variation range can be obtained by setting up a water level monitoring network outside the pit. When the water level is abnormal, the water level cause analysis can be carried out and corresponding emergency measures can be taken. For example, when the water level drops sharply due to excessive pumping of the precipitation well or curtain leakage, remedial measures such as shutting down some precipitation wells, recharging outside the pit, and grouting the leakage point can be taken. Other methods can also be used to obtain the water level variation range and take other measures to ensure the safety of the surrounding environment in abnormal situations. This is not limited to the embodiments of this application.

[0083] Optionally, the location of the drainage hole can be selected to be directly above the corresponding precipitation well point in the pit, and the drainage hole can be formed through the steps of bottom plate cushion layer - pre-buried PVC pipe - filled gravel filter layer - covered with geotextile - bottom plate steel bar bundle blasting - concrete pouring, etc. The drainage hole can prevent the bottom plate from being damaged by water pressure buoyancy, collect residual seepage under the bottom plate, prevent the cushion layer from bulging, and when the precipitation well is gradually closed, the groundwater level recovery can also be observed through the drainage hole. Among them, the drainage hole can also be formed by other manufacturing steps, which are not limited in the embodiment of the present application.

[0084] Step 205: 28 first inclinometer points are arranged in the foundation pit to monitor the lateral displacement of the retaining wall, and 28 second inclinometer points are arranged in the deep soil of the foundation pit to monitor the horizontal position of the soil.

[0085] Among them, deep soil refers to the soil below 5 meters underground. Figure 3 A layout diagram of foundation pit monitoring points provided in an embodiment of the present application is shown as follows: Figure 3 As shown, ZC1 to ZC28 are the marking numbers of the first inclinometer points, and SC1 to SC28 are the marking numbers of the second inclinometer points.

[0086] Step 206: Arrange 56 surface settlement monitoring sections behind the wall at locations 10 meters apart from the foundation pit along the perimeter of the foundation pit.

[0087] There are 5 settlement monitoring points in each section, and the intervals between the 5 settlement monitoring points are 2 meters, 3 meters, 5 meters, 5 meters and 8 meters respectively. Figure 3 As shown, DB1-i to DB56-i (i is the measuring point number) are the marking numbers of 56 surface settlement monitoring sections behind the wall.

[0088] Step 207: 28 groundwater level monitoring points outside the foundation pit are arranged at locations 30 meters apart from the foundation pit along the perimeter of the foundation pit.

[0089] like Figure 3 As shown, SW1 to SW28 are the marking numbers of 28 groundwater level monitoring points outside the pit.

[0090] Step 208: Set up seven internal support horizontal axial force detection sections in the foundation pit.

[0091] like Figure 3 As shown, ZL1-m~ZL7-m (m is the number of support layers) are the marking numbers of the 7 internal support horizontal axial force detection sections.

[0092] Step 209: Obtain the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the internal support axial force during the construction process through multiple monitoring points.

[0093] Step 209 may include:

[0094] 1.1) Obtaining lateral displacement data of the retaining wall measured at multiple first inclination measurement points;

[0095] Figure 4 This embodiment of the present application provides Figure 3 The lateral displacement curve of the pile retaining wall is formed by the lateral displacement data of the retaining wall measured at the first 6 inclination measurement points, among which ZC1~ZC28 are Figure 3 The mark number of the first inclination measurement point, Figure 4 The figure marked (a) ZC4 is a curve formed by the data obtained from the first inclination measurement point ZC4. Figure 4 The figure marked (b) ZC8 is a curve formed by the data detected at the first inclination measuring point ZC8. Figure 4 The figure marked (c) ZC17 is a curve formed by the data obtained by the first inclination measurement point ZC17. Figure 4 The figure marked (d) ZC19 is a curve formed by the data detected at the first inclination measuring point ZC18. Figure 4 The figure marked (e) ZC21 is a curve formed by the data detected at the first inclination measuring point ZC21. Figure 4 The figure marked (f) ZC27 is a curve formed by the data detected at the first inclination measuring point ZC27.

[0096] 1.2) Based on the lateral displacement data of the retaining wall, determining data of a maximum lateral displacement section, where the maximum lateral displacement section is a section where the lateral displacement of the retaining wall is greater than a first lateral position threshold, the data of the maximum lateral displacement section including lateral displacement values of the retaining wall at a plurality of first inclination measurement points arranged along the depth direction of the foundation pit;

[0097] like Figure 3 and Figure 4As shown in the figure, the lateral displacement of the retaining wall increases significantly with increasing excavation depth, with its distribution curve exhibiting a "bulging" shape. Initially, the lateral earth pressure caused by the unloading of the pit soil gradually increases, causing the retaining wall to continuously experience lateral displacement. As excavation depth increases, the application of internal supports and the restraining effect of the pit bottom soil on the retaining wall limit the exacerbation of lateral displacement to a certain extent, resulting in a lateral displacement curve that initially increases and then decreases. The maximum lateral displacement at each measuring point is concentrated between depths of 2 and 4 meters, with the maximum lateral displacements being 3.92 mm, 4.06 mm, 4.92 mm, 5.45 mm, 4.64 mm, and 3.55 mm, respectively. This phenomenon is primarily due to the disruption of the stress and strain equilibrium of the original soil layer during excavation. With the introduction of internal supports and the gradual embedding of the pit bottom soil into the retaining wall, the deformation of the retaining wall is coordinated and the earth pressure behind the wall is dynamically adjusted. In addition, it can be seen from step 201 that since the retaining wall pile lengths, excavation depths, and number of supporting layers at each measuring point are different, the geology of the pit bottom soil layer is also different, resulting in obvious differences in the distribution of the lateral displacement curves of the retaining walls at each measuring point. The first lateral position threshold can be a range interval value obtained by summarizing historical experience data, and this embodiment of the present application is not limited here. It should be noted that the various thresholds involved in the embodiment of the present application can all be empirical values, for example, they can be representative and universally valuable values accumulated by the construction unit in long-term engineering practice.

[0098] 1.3) Obtaining soil horizontal displacement data measured at multiple second inclinometer points;

[0099] Figure 4 This embodiment of the present application provides Figure 3 The horizontal displacement curve of deep soil is formed by the soil horizontal displacement data measured by the 6 second inclination measurement points, among which SC1 to SC28 are Figure 3 The mark number of the second inclinometer point, and Figure 4 The figure marked (a) ZC4 is a curve formed by the data obtained from the second inclination measurement point SC4. Figure 4 The figure marked (b) SC8 is a curve formed by the data detected at the second inclination measuring point SC8. Figure 4 The figure marked (c) SC17 is a curve formed by the data detected at the second inclination measuring point SC17. Figure 4 The figure marked (d) SC19 is a curve formed by the data detected by the second inclination measuring point SC18. Figure 4 The figure marked (e) SC21 is a curve formed by the data detected at the second inclination measuring point SC21. Figure 4 The figure marked (f) SC27 is a curve formed by the data detected by the second inclination measuring point SC27.

[0100] 1.4) determining soil horizontal displacement data of a maximum soil horizontal displacement section based on the soil horizontal displacement data, wherein the maximum soil horizontal displacement section is a section in which the soil horizontal displacement is greater than a first soil horizontal displacement threshold, and the soil horizontal displacement data of the maximum soil horizontal displacement section includes soil horizontal displacement values of a plurality of second inclinometer points arranged along the depth direction of the foundation pit;

[0101] like Figure 3 and Figure 5 As shown, the horizontal displacement of the deep soil outside the pit increases significantly with the increase of excavation depth, and the distribution curve presents a "bulging" shape; each measuring point reaches its maximum horizontal displacement when excavated to the bottom plate, which is 3.66 mm (depth 4 meters), 4.46 mm (depth 4 meters), 4.95 mm (depth 5 meters), 9.55 mm (depth 3.5 meters), 5.31 mm (depth 3.5 meters), and 4.48 mm (depth 4 meters). The horizontal displacement of the deep soil at measuring points SC17, SC19, and SC21 is higher than that of other measuring points. By comparison, it is found that the greater the excavation depth of the foundation pit, the greater the maximum horizontal displacement of the deep soil, and the position of the maximum horizontal displacement of the deep soil gradually moves downward with the excavation depth. This is because the accumulation of the foundation pit excavation depth gradually releases the soil pressure behind the wall, changing the overall stress equilibrium state of the soil. In addition, the support effect of the internal support promotes the increase and dynamic adjustment of the lateral displacement of the soil. The first soil horizontal displacement threshold can be a range value obtained by summarizing historical experience data, which is not limited in this embodiment of the present application.

[0102] 1.5) Obtain surface settlement data behind the retaining wall at multiple settlement monitoring sections.

[0103] Among them, the surface settlement data behind the retaining wall of each settlement monitoring section includes the surface settlement parameters behind the retaining wall recorded by 5 settlement monitoring points, and each surface settlement parameter behind the retaining wall includes a curve of the surface settlement value behind the retaining wall recorded by the monitoring point changing with time.

[0104] Figure 6 This embodiment of the present application provides Figure 3 The surface settlement data behind the retaining wall form a curve of surface settlement change over time, of which DB1 to DB56 are Figure 3 The marking numbers of the 56 surface settlement monitoring sections behind the wall, Figure 6 In the figure, the graph with reference number a is a graph formed by the data of reference number DB49, and the graph with reference number b is a graph formed by the data of reference number DB53. Figure 3 and Figure 6As shown, the surface settlement behind the retaining wall shows an overall increasing trend with the progress of foundation pit excavation. With the passage of excavation time, the surface settlement gradually stabilizes, indicating that the foundation pit excavation stage is the main stage of surface settlement increase. The maximum surface settlement after stabilization ranges from -5.87 mm to -10.22 mm. Furthermore, there are certain differences in surface settlement at different measuring points. Combining the settlement curves of each measuring point, its distribution location, excavation depth, and soil physical properties, these differences are closely related to the distance of the measuring point from the foundation pit edge, the distribution of groundwater levels, and the application of support structures. Initially, the surface settlement increases linearly, then gradually slows and eventually stabilizes. This trend reflects the stress release and redistribution process in the soil during foundation pit excavation. Measuring points DB49 and DB53 fully demonstrate this variation.

[0105] 1.6) Obtain groundwater level data outside the foundation pit through groundwater level monitoring points outside the pit.

[0106] The groundwater level data outside the foundation pit, obtained at each monitoring point, includes a time-varying curve of the groundwater level at that monitoring point. During pit construction, dewatering measures implemented within the pit alter the internal and external hydraulic gradient balance, triggering seepage of groundwater outside the pit. This long-term effect can cause settlement and deformation of the surrounding soil. To investigate the impact of pit excavation and dewatering on the groundwater level outside the pit, multiple groundwater level monitoring points can be deployed around the perimeter of the pit.

[0107] 1.7) Based on the groundwater level data outside the foundation pit, determine the cumulative change curve of the groundwater level over time and the change curve of the groundwater level change rate over time.

[0108] During construction, the cumulative change in groundwater levels outside the pit exhibited significant fluctuations over time, particularly at measuring point SW26, where the cumulative change in groundwater levels plummeted over a short period of time but remained within the monitoring and warning value of ±1.0 m. Furthermore, the cumulative change in groundwater levels generally exhibited two phases: rapid growth or decline followed by gradual stabilization. However, the duration of these two phases varied significantly across measuring points. The rate of change at each measuring point fluctuated within a range of ±0.2 m / d, remaining within the monitoring and warning value of ±0.5 m / d.

[0109] 1.8) Obtain the internal support axial force through 7 internal support horizontal axial force detection sections.

[0110] As the excavation progressed, the active earth pressure around the pit continued to rise. Under the combined effects of lateral loads and the internal support structure, the support axial force increased in a step-like manner over time before gradually stabilizing. The axial forces at each level ranged from -381.90 to 3525.90 kN (kilonewtons) for the first support, 25.62 to 512.03 kN for the second support, and 95.76 to 531.76 kN for the third support. The maximum axial forces for the first, second, and third supports were approximately 59.8%, 20.5%, and 21.3% of the design values, respectively, demonstrating a high safety margin. A comparison of the axial forces at each layer revealed that the axial force of the first concrete support varied significantly, with growth occurring in three stages: rapid, slow, and stabilizing, reaching stability after 50 days. The axial forces of the second and third steel supports grew more gradually, with virtually no significant changes after 20 days. From the above axial force changes, it can be seen that the lateral earth pressure load caused by the unloading of the foundation pit excavation is mainly borne by the first concrete support, and the second and third steel supports only bear part of the residual lateral earth pressure and the stress growth caused by the rebound of the pit bottom.

[0111] Step 210: Determine whether any of the following parameters, including the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the internal support axial force, deviate from a preset threshold by more than a preset threshold. If no such deviation exists, proceed to step 209. If so, proceed to step 211.

[0112] Among them, the preset threshold can be a threshold range obtained by summarizing historical data, and the specific preset threshold is not limited in the embodiment of this application.

[0113] Step 210 includes:

[0114] 2.1) Determine whether the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold.

[0115] The preset lateral displacement data includes a preset lateral displacement value composed of the lateral displacement values of the retaining wall of multiple first inclinometer points arranged along the depth direction of the foundation pit. When the lateral displacement is greater than, it is determined that the lateral displacement of the retaining wall is greater than the preset threshold value of the lateral displacement of the retaining wall. When the lateral displacement is not greater than, it is determined that the lateral displacement of the retaining wall is not greater than the preset threshold value of the lateral displacement of the retaining wall.

[0116] 2.2) obtaining a lateral displacement curve of the maximum lateral displacement section based on the lateral displacement data of the maximum lateral displacement section, wherein the lateral displacement curve of the maximum lateral displacement section includes a curve formed by a plurality of lateral position values included in the lateral displacement data of the maximum lateral displacement section;

[0117] 2.3) obtaining a lateral displacement curve of the preset lateral displacement data based on the preset lateral displacement data, wherein the lateral displacement curve of the preset lateral displacement data includes a curve formed by a plurality of preset lateral position values included in the preset lateral displacement data;

[0118] 2.4) determining a first fitting ratio between the lateral displacement curve of the maximum lateral displacement section and the lateral displacement curve of the preset lateral displacement data;

[0119] The index value is obtained by quantifying the similarity or fit between the two curves (lateral displacement curve vs. preset lateral displacement curve). The higher the index value, the closer the actual deformation shape is to the preset allowable shape; the lower the index value, the greater the difference between the actual deformation shape and the preset shape.

[0120] 2.5) when the first fitting rate is greater than a first fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold;

[0121] The first fitting rate threshold may be a critical value of the degree of curve fitting that is pre-set based on a summary of historical data, and the specific value is not limited in this embodiment of the present application.

[0122] 2.6) When the fitting rate is less than or equal to a first fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than a preset lateral displacement deviation threshold.

[0123] 2.7) Determine whether the deviation between the soil horizontal displacement data of the maximum soil horizontal displacement section and the preset soil horizontal displacement data is greater than the preset horizontal displacement deviation.

[0124] The preset soil horizontal displacement data includes a preset soil horizontal displacement value composed of soil horizontal displacement values of multiple second inclinometer points arranged along the depth direction of the foundation pit. When it is greater than, it is determined that the soil horizontal displacement is greater than the preset threshold value of the soil horizontal displacement. When it is not greater than, it is determined that the soil horizontal displacement is not greater than the preset threshold value of the soil horizontal displacement.

[0125] 2.8) obtaining a soil horizontal displacement curve for the maximum soil horizontal displacement section based on the soil horizontal displacement data for the maximum soil horizontal displacement section, wherein the soil horizontal displacement curve for the maximum soil horizontal displacement section includes a curve formed by a plurality of soil horizontal displacements included in the soil horizontal displacement data for the maximum soil horizontal displacement section;

[0126] 2.9) obtaining a soil horizontal displacement curve of the preset soil horizontal displacement data based on the preset soil horizontal displacement data, wherein the soil horizontal displacement curve of the preset soil horizontal displacement data includes a curve formed by a plurality of preset soil horizontal displacement values included in the preset soil horizontal displacement data;

[0127] 2.10) Determining a second fitting ratio between the soil horizontal displacement curve of the maximum soil horizontal displacement section and the soil horizontal displacement curve of the preset soil horizontal displacement data;

[0128] 2.11) when the second fitting rate is greater than a second fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold;

[0129] 2.12) When the second fitting rate is less than or equal to a second fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than a preset lateral displacement deviation threshold.

[0130] 2.13) Determine whether the surface settlement data behind the retaining wall of multiple settlement monitoring sections are all greater than the surface settlement threshold behind the retaining wall.

[0131] 2.14) Determine whether the cumulative change curve of the groundwater level over time satisfies a preset change curve, and determine whether the change curve of the groundwater level change rate over time satisfies a preset change rate curve.

[0132] 2.15) Determine whether the internal support axial forces obtained from the seven internal support horizontal axial force detection sections all meet the internal support axial force threshold.

[0133] Step 211: If it exists, make adjustments through preset measures and re-execute step 209.

[0134] The preset measures include at least one of reinforcing the support structure, adjusting the excavation depth, the excavation sequence and the layering parameters, and grouting.

[0135] The lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the internal support during the construction process were again obtained through multiple monitoring points.

[0136] In summary, the construction method of the water-rich gravel layer foundation pit provided by the embodiment of the present application sets up multiple monitoring points in the construction area, and obtains the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the inner support in real time during the construction process through these monitoring points, and judges whether there is a deviation of any one of the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the inner support from the preset threshold of any one of the parameters greater than the preset threshold; when it exists, it can be judged by including reinforcing the support structure The structure is adjusted, the excavation depth, the excavation order and the layering parameters are adjusted, and at least one preset measure in the grouting is adjusted, and the steps of obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit and the axial force of the internal support during the construction process are re-executed through multiple monitoring points. In this way, the construction process of the foundation pit can be monitored in real time, and intervention adjustments can be made in real time, making it easier for the foundation pit to meet the preset requirements. This method can be applied to the construction process of various water-rich gravel layer foundation pits, and reduces the difficulty of the foundation pit construction meeting the preset requirements.

[0137] In this application, the term "at least one of A and B" simply describes an association relationship between associated objects, indicating that three possible relationships exist. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, and B exists alone. Similarly, "at least one of A, B, and C" means that seven possible relationships exist, indicating: A exists alone, B exists alone, C exists alone, A and B exist simultaneously, A and C exist simultaneously, C and B exist simultaneously, and A, B, and C exist simultaneously. Similarly, "at least one of A, B, C, and D" means that fifteen possible relationships exist, indicating: A exists alone, B exists alone, C exists alone, D exists alone, A and B exist simultaneously, A and C exist simultaneously, A and D exist simultaneously, C and B exist simultaneously, D and B exist simultaneously, C and D exist simultaneously, C and D exist simultaneously, A, B, and C exist simultaneously, A, B, and D exist simultaneously, A, C, and D exist simultaneously, B, C, and D exist simultaneously, and A, B, C, and D exist simultaneously.

[0138] In this application, the terms "first", "second", "third" and "fourth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless otherwise expressly limited.

[0139] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A construction method for a foundation pit in a water-rich gravel layer, characterized in that: The method is used for a foundation pit in a two-way four-lane highway tunnel project, comprising: Determining a construction area of the foundation pit, wherein the construction area includes a first construction section, a second construction section, and a third construction section; Determine the support structure of the construction area, the support structure of the first construction section and the third construction section is a composite retaining wall of bored cast-in-place piles and high-pressure rotary jet pile water-stop curtains, the support structure of the second construction section is a retaining wall of interlocking piles, and the support structure in the foundation pit is concrete supports and steel supports; Excavate the foundation pit by excavating the earth in layers, sections and blocks based on time and space effects; Setting up a plurality of monitoring points in the construction area; Obtaining the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the axial force of the internal support during the construction process through the multiple monitoring points; Determining whether any one of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force deviates from a preset threshold of the any one parameter by a degree greater than a preset threshold; When existing, adjustments are made through preset measures, and the steps of obtaining the lateral displacement of the retaining wall, horizontal displacement of the soil, surface settlement behind the retaining wall, groundwater level outside the foundation pit and axial force of the internal support during the construction process through the multiple monitoring points are re-executed, and the preset measures include reinforcing the support structure, adjusting the excavation depth, excavation order and layering parameters and at least one of grouting.

2. The method according to claim 1, characterized in that The method further comprises: when the monitoring points do not exist, executing the step of acquiring the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the axial force of the internal support during the construction process through the plurality of monitoring points; The plurality of monitoring points are set in the construction area, including: 28 first inclinometer points are arranged in the foundation pit to monitor the lateral displacement of the retaining wall, and 28 second inclinometer points are arranged in the deep soil of the foundation pit to monitor the horizontal position of the soil, wherein the deep soil is the soil below 5 meters underground; 56 surface settlement monitoring sections behind the wall are arranged at intervals of 10 meters along the perimeter of the foundation pit, with 5 settlement monitoring points set at each section, and the spacing between the settlement monitoring points among the 5 settlement monitoring points is 2 meters, 3 meters, 5 meters, 5 meters and 8 meters respectively; 28 groundwater level monitoring points outside the pit are arranged at intervals of 30 meters along the perimeter of the foundation pit; Seven internal support horizontal axial force detection sections are set in the foundation pit.

3. The method according to claim 1, characterized in that In the construction area, the design speed of the two-way four-lane highway tunnel is 60 kilometers per hour, the full length of the two-way four-lane highway tunnel is 510 meters, the open section of the two-way four-lane highway tunnel is 305 meters, and the buried section is 205 meters. The two-way four-lane highway tunnel is constructed using the open-cut method, the excavation width of the foundation pit ranges from 20.4 meters to 30.8 meters, and the depth of the foundation pit ranges from 1.8 meters to 11.6 meters. The strata in the construction area include backfill soil, silty clay, round gravel, pebbles, strongly weathered mudstone and moderately weathered mudstone from top to bottom. The groundwater in the construction area is pore groundwater, and the groundwater level is within the range of 1 meter to 6.2 meters below the surface. The annual variation of the groundwater level is 2 meters.

4. The method according to claim 3, characterized in that The first construction section includes the section from 92 meters to 260 meters of the highway tunnel, the second construction section includes the section from 261 meters to 402 meters of the highway tunnel, and the third construction section includes the section from 403 meters to 507 meters of the highway tunnel; In the first construction section, the excavation depth ranges from 1.8 meters to 8 meters, the pile lengths of the multiple bored piles and high-pressure rotary jet piles in the first construction section range from 6 meters to 10.5 meters, and the diameter of each bored pile is 800 mm, the center distance between adjacent bored piles in the multiple bored piles is 1000 mm, the diameter of each high-pressure rotary jet pile is 600 mm, the center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes a steel pipe, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

5. The method according to claim 4, characterized in that In the second construction section, the excavation depth ranges from 8 meters to 11.6 meters. The interlocking pile retaining wall includes a plurality of interlocking piles. The diameter of the interlocking piles is 1000 mm. The pile length of the interlocking piles ranges from 11 meters to 13.5 meters. The center distance between two adjacent interlocking piles in the plurality of interlocking piles is 750 mm. The concrete support includes a C30 concrete block. The length and width of the C30 concrete block are both 0.8 meters. The steel support includes 2 or 3 steel pipes. The diameter of the steel pipe is 609 mm and the wall thickness is 16 mm.

6. The method according to claim 4, characterized in that In the third construction section, the excavation depth ranges from 2.5 meters to 8 meters, the pile lengths of the multiple bored piles and high-pressure rotary jet piles in the third construction section range from 9.5 meters to 10 meters, and the diameter of each bored pile is 800 mm, the center distance between adjacent bored piles in the multiple bored piles is 1000 mm, the diameter of each high-pressure rotary jet pile is 600 mm, the center distance between adjacent high-pressure rotary jet piles in the multiple high-pressure rotary jet piles is 1000 mm, the concrete support includes a C30 concrete block, the length and width of the C30 concrete block are both 0.8 meters, and the steel support includes a steel pipe, the diameter of the steel pipe is 609 mm, and the wall thickness is 16 mm.

7. The method according to claim 2, characterized in that The acquisition of the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the internal support axial force during the construction process through the multiple monitoring points includes: Acquiring lateral displacement data of the retaining wall measured at a plurality of the first inclinometer points; Determining data of a maximum lateral displacement section based on the lateral displacement data of the retaining wall, wherein the maximum lateral displacement section is a section in which the lateral displacement of the retaining wall is greater than a first lateral position threshold, and the data of the maximum lateral displacement section includes lateral displacement values of the retaining wall at a plurality of first inclination measurement points arranged along a depth direction of the foundation pit; The determining whether the deviation of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force from a preset threshold value of any one of the parameters is greater than a preset threshold value includes: Determine whether the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold, the preset lateral displacement data including a preset lateral displacement value composed of the lateral displacement values of the retaining wall of multiple first inclination measuring points arranged along the depth direction of the foundation pit. When the deviation is greater than, determine that the lateral displacement of the retaining wall is greater than the preset threshold value of the lateral displacement of the retaining wall; when the deviation is not greater than, determine that the lateral displacement of the retaining wall is not greater than the preset threshold value of the lateral displacement of the retaining wall.

8. The method according to claim 7, characterized in that Determining whether a deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is greater than a preset lateral displacement deviation threshold includes: obtaining a lateral displacement curve of the maximum lateral displacement section based on the lateral displacement data of the maximum lateral displacement section, wherein the lateral displacement curve of the maximum lateral displacement section includes a curve formed by a plurality of lateral position values included in the lateral displacement data of the maximum lateral displacement section; obtaining a lateral displacement curve of the preset lateral displacement data based on the preset lateral displacement data, wherein the lateral displacement curve of the preset lateral displacement data includes a curve formed by a plurality of preset lateral position values included in the preset lateral displacement data; determining a first fitting ratio between a lateral displacement curve of the maximum lateral displacement section and a lateral displacement curve of the preset lateral displacement data; When the first fitting rate is greater than a first fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and preset lateral displacement data is greater than a preset lateral displacement deviation threshold; When the fitting rate is less than or equal to the first fitting rate threshold, it is determined that the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than the preset lateral displacement deviation threshold.

9. The method according to claim 2, characterized in that The acquisition of the lateral displacement of the retaining wall, the horizontal displacement of the soil, the surface settlement behind the retaining wall, the groundwater level outside the foundation pit, and the internal support axial force during the construction process through the multiple monitoring points includes: Acquire soil horizontal displacement data measured by a plurality of the second inclinometer points; Determining soil horizontal displacement data of a maximum soil horizontal displacement section based on the soil horizontal displacement data, wherein the maximum soil horizontal displacement section is a section in which the soil horizontal displacement is greater than a first soil horizontal displacement threshold, and the soil horizontal displacement data of the maximum soil horizontal displacement section includes soil horizontal displacement values of a plurality of second inclinometer points arranged along a depth direction of the foundation pit; The determining whether the deviation of the parameters of the retaining wall lateral displacement, soil horizontal displacement, surface settlement behind the retaining wall, groundwater level outside the foundation pit, and internal support axial force from a preset threshold value of any one of the parameters is greater than a preset threshold value includes: Determine whether the deviation between the soil horizontal displacement data of the maximum soil horizontal displacement section and the horizontal displacement data of the preset soil is greater than the preset horizontal displacement deviation, the preset soil horizontal displacement data including the preset soil horizontal displacement value composed of the soil horizontal displacement values of a plurality of second inclinometer points arranged along the depth direction of the foundation pit; if the deviation is greater than, determine that the soil horizontal displacement is greater than the preset threshold value of the soil horizontal displacement; if the deviation is not greater than, determine that the soil horizontal displacement is not greater than the preset threshold value of the soil horizontal displacement.

10. The method according to claim 9, characterized in that The determining whether the deviation between the soil horizontal displacement data of the maximum soil horizontal displacement section and the preset soil horizontal displacement data is greater than a preset horizontal displacement deviation includes: obtaining a soil horizontal displacement curve of the maximum soil horizontal displacement section based on the soil horizontal displacement data of the maximum soil horizontal displacement section, wherein the soil horizontal displacement curve of the maximum soil horizontal displacement section includes a curve formed by a plurality of soil horizontal displacements included in the soil horizontal displacement data of the maximum soil horizontal displacement section; obtaining a soil horizontal displacement curve of the horizontal displacement data of the preset soil body based on the horizontal displacement data of the preset soil body, wherein the soil horizontal displacement curve of the horizontal displacement data of the preset soil body includes a curve composed of a plurality of preset soil horizontal displacement values included in the horizontal displacement data of the preset soil body; Determining a second fitting ratio between a soil horizontal displacement curve of the maximum soil horizontal displacement section and a soil horizontal displacement curve of the preset soil horizontal displacement data; When the second fitting rate is greater than a second fitting rate threshold, determining that a deviation between the lateral displacement data of the maximum lateral displacement section and preset lateral displacement data is greater than a preset lateral displacement deviation threshold; When the second fitting rate is less than or equal to the second fitting rate threshold, it is determined that the deviation between the lateral displacement data of the maximum lateral displacement section and the preset lateral displacement data is not greater than the preset lateral displacement deviation threshold.

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