Construction method of super-long foundation pit support servo system close to protected object

Abstract

The application relates to a construction method of an ultra-long foundation pit support servo system close to a protected object, the system comprising a surrounding structure, a bracing system, a concrete surrounding purlin and a hydraulic oil cylinder, the bracing system comprising first, second and third bracing substructures separated along the length direction, the first bracing substructures being arranged at intervals, the second bracing substructures being located on the two sides of the first bracing substructures, and the third bracing substructure being located between the two second bracing substructures; the hydraulic oil cylinder being arranged between the concrete surrounding purlins of the first, second and third bracing substructures and the surrounding structure; and the first, second and third bracing substructures being loaded in batches in sequence until the bracing system is formed. The application cancels the staged wall, accelerates the construction speed and reduces the cost; the first, second and third bracing substructures are arranged to implement the large pit in sections, the bracing system is quickly formed, the length of the foundation pit is reduced, the long-side effect of the foundation pit is reduced, large slope excavation can be carried out, and the construction speed is accelerated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit engineering support, in particular to a construction method of a super-long foundation pit support servo system close to a protected object. BACKGROUND

[0002] In the city foundation pit support technology, the concrete support technology is one of the commonly used foundation pit support measures, with the continuous development of urban underground space, the situation of foundation pit close to protected objects is faced in the process of engineering construction, and the requirement for foundation pit deformation control is also higher and higher, so the concrete support servo system emerges as the times require. When the foundation pit is close to the protected object on one side, the one-way concrete support servo system is usually used to control the deformation of the foundation pit on the side close to the protected object, so as to achieve the purpose of reducing the deformation of the protected object.

[0003] When the side length of the deep foundation pit close to the protected object is not large (such as less than 100m), the concrete support servo control system can be used, and the loading process is usually completed once after the support system of the layer is formed; however, when the side length of the foundation pit close to the protected object is too large (such as greater than 100m), it is not suitable to use the construction scheme of one-time loading. In addition, for the deep foundation pit of soft soil, the soft soil layer mainly composed of mucky clay, mucky silty clay and the like has obvious rheological property and creep property, that is, there is always deformation after the foundation pit is excavated.

[0004] Generally, when there is a protected object 01 in the soft soil deep foundation pit engineering, the area of the deep foundation pit is not greater than 10000m 2 , and the side length is not greater than 100m, so when the area and side length of the foundation pit are large, the current conventional method is to divide the area by increasing the staged wall 03 in the enclosure structure 02, as shown in Figure 1 , that is, to implement in batches. In addition, in the concrete support servo control soft soil deep foundation pit engineering, the support structure of one layer is usually formed once, and then loaded, and after the loading is completed, the lower soil excavation is carried out, which cannot realize the support as the excavation, and cannot meet the micro-deformation control requirement of the close protected object.

[0005] Therefore, how to provide a construction method of a super-long foundation pit support servo system close to a protected object, which can reduce the deformation of the foundation pit, is a technical problem to be solved by those skilled in the art. SUMMARY

[0006] The present application provides a construction method of a super-long foundation pit support servo system close to a protected object to solve the above technical problems.

[0007] To solve the above technical problems, the present application provides a construction method of a super-long foundation pit support servo system close to a protected object, which comprises an enclosure structure, a counter-support system, a concrete enclosure purlin and a hydraulic oil cylinder,

[0008] The supporting system includes a first pair of supporting substructures, a second pair of supporting substructures, and a third pair of supporting substructures separated along the length direction. The first pair of supporting substructures are spaced apart, the second pair of supporting substructures are located on both sides of the first pair of supporting substructures, and the third pair of supporting substructures are located between the two second pair of supporting substructures.

[0009] The hydraulic cylinders are provided between the concrete walers and the retaining structure of the first pair of support structures, the second pair of support structures and the third pair of support structures;

[0010] The construction method includes the following steps:

[0011] Excavate the first layer of soil in the area where the first pair of support structures are located, construct the first pair of support structures and install the hydraulic cylinders;

[0012] Construction of the first-floor earthwork and supports in the area where the second pair of support structures are located, and installation of the hydraulic cylinders;

[0013] Construction of the first-floor earthwork and supports in the area where the third pair of support structures are located, and installation of the hydraulic cylinders;

[0014] After the first pair of support structures is formed in the area where the first pair of support structures are located, the excavation of the next layer of earthwork in the area where the first pair of support structures are located begins.

[0015] After the second pair of support structures is formed in the first layer of the area where the second pair of support structures are located, the excavation of the next layer of earthwork in the area where the second pair of support structures are located begins.

[0016] After the third pair of supports is formed in the area where the third pair of supports is located, the excavation of the next layer of earthwork in the area where the third pair of supports is located begins.

[0017] Repeat the above construction procedures until all earthwork excavation is completed and the support system is formed.

[0018] Preferably, the concrete used in the bracing system is early-strength concrete.

[0019] Preferably, the hydraulic cylinder is mounted on the concrete waler via a support box, with its extended end contacting the embedded steel plate at the end of the concrete support; a sliding layer is provided below the hydraulic cylinder, and limiting blocks are provided on both sides.

[0020] Preferably, the enclosure structure and the concrete waler are further connected by tie rods.

[0021] Preferably, a junction node is provided at the connection of the concrete waler between the substructures constructed first and later. The junction node includes longitudinal reinforcement, connecting joints, the substructure constructed first, and the substructure constructed later. The connecting joints are embedded at both ends of the substructure constructed first, and the connecting joints at both ends are welded to the longitudinal reinforcement of the substructure constructed first and the substructure constructed later, respectively.

[0022] Preferably, the retaining structure is also equipped with a pressure testing device for measuring the active earth pressure on the side of the diaphragm wall. The pressure testing device includes a fiber optic measuring line, an earth pressure sensor, a data acquisition and processing system, a flat steel bar, a non-rigid waterproof membrane, a limiting bar, and a ground wall reinforcement cage. The flat steel bar is connected to the ground wall reinforcement cage near the soil outside the pit in the diaphragm wall adjacent to the protected object, by the limiting bar. The fiber optic measuring line and the earth pressure sensor are arranged on the outside of the flat steel bar. After installation, the non-rigid waterproof membrane is covered, and the flat steel bar and the ground wall reinforcement cage are placed into the soil together when the diaphragm wall is excavated. The signal detected by the earth pressure sensor is transmitted to the data acquisition and processing system through the fiber optic measuring line.

[0023] Preferably, it also includes a method for loading the support system, including:

[0024] After the concrete construction of the supporting system is completed, the concrete strength is tested. When the concrete strength reaches F... c0 Preloading begins at this time:

[0025] The concrete strength of the first pair of bracing structures reached F. c0 Apply hydraulic cylinder force to P0;

[0026] The concrete strength of the second pair of bracing structures reaches F. c0 Apply hydraulic cylinder force to P0;

[0027] The concrete strength of the third pair of bracing structures reaches F. c0 Apply hydraulic cylinder force to P0.

[0028] Preferably, when the concrete strength reaches F cn Apply servo force to lock value P n :

[0029] The concrete strength of the first pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n ;

[0030] The concrete strength of the second pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n ;

[0031] The concrete strength of the third pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n .

[0032] Preferably, the locking value P n The calculation methods include: P n =γ×p k ×L / n, where γ is the coefficient, p k The average confining pressure standard value is given, where L is the length of the ground wall and n is the number of hydraulic cylinders.

[0033] Compared with existing technologies, the construction method of the ultra-long foundation pit support servo system adjacent to the protected object provided by the present invention has the following advantages:

[0034] 1. This invention eliminates the phased wall, speeds up construction, and reduces construction costs; by setting up the first, second, and third pair of support structures to divide the large pit into sections, a support system is quickly formed, thereby reducing the length of the foundation pit, reducing the long side effect of the foundation pit, and also allowing for large-slope excavation, thus speeding up construction.

[0035] 2. This invention first forms a bracing system and completes servo loading, then the lower layer of soil and support in the bracing area can be constructed, which speeds up the construction process, reduces the time the soil is exposed, and thus effectively controls the deformation of the foundation pit adjacent to the protected object.

[0036] 3. This invention provides a method for batch loading of servo force and determines the calculation method for servo force lock value, thereby ensuring the stability and safety of foundation pit construction. Attached Figure Description

[0037] Figure 1 A schematic diagram of the phased implementation of existing deep foundation pits in soft soil;

[0038] Figure 2 This is a schematic diagram of the partitioning of the ultra-long foundation pit support servo system adjacent to the protected object in a specific embodiment of the present invention;

[0039] Figures 3a to 3c These are schematic diagrams illustrating the phased implementation of the ultra-long foundation pit support servo system adjacent to the protected object in a specific embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram illustrating the connection between the concrete support and the concrete waler in a specific embodiment of the present invention.

[0041] Figure 5 This is a schematic diagram of the installation of a hydraulic cylinder in a specific embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the boundary node in a specific embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of the disassembled structure of the connector in a specific embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the pressure testing device in a specific embodiment of the present invention;

[0045] Figure 9 This is a cross-sectional schematic diagram of a pressure testing device according to a specific embodiment of the present invention;

[0046] Figure 10 This is a schematic diagram of the active earth pressure calculation model on the side of the earth wall in a specific embodiment of the present invention.

[0047] Figure 1 In Chinese: 01-Protected object, 02-Enclosure structure, 03-Phase wall;

[0048] Figures 2-10 In Chinese: 01-Protected object; 10-Enclosure structure; 20-Bracket system; 21-First pair of bracing substructure; 22-Second pair of bracing structure; 23-Third pair of bracing structure; 24-Concrete support; 30-Concrete waler; 31-Boundary node; 32-Longitudinal reinforcement; 33-Connecting joint; 34-Pre-constructed substructure; 35-Post-constructed substructure; 40-Hydraulic cylinder; 41-Support box; 42-Limiting block; 43-Slip layer; 44-Embedded steel plate; 45-Hanging bar; 51-Mort; 52-Tenon; 53-First connector; 54-Second connector; 60-Pressure testing device; 61-Fiber optic measuring line; 62-Soil pressure sensor; 63-Data acquisition and processing system; 64-Flat steel; 65-Non-rigidity waterproof membrane; 66-Limiting reinforcement; 67-Ground wall reinforcement cage. Detailed Implementation

[0049] To illustrate the technical solutions of the invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the invention and not to limit the scope of the invention.

[0050] This invention provides a servo system for supporting ultra-long foundation pits adjacent to the protected object, such as... Figure 2 As shown, it includes a retaining structure 10, a bracing system 20, a concrete waler 30, and a hydraulic cylinder 40. By installing the hydraulic cylinder 40 on the concrete waler 30 of the bracing system 20, the retaining structure 10 on the side where the protected object 01 is located is actively supported to avoid deformation of the foundation pit.

[0051] The supporting system 20 includes a first pair of supporting substructures 21, a second pair of supporting substructures 22, and a third pair of supporting structures 23, separated along the length direction. The first pair of supporting substructures 21 are spaced apart, the second pair of supporting substructures 22 are located on both sides of the first pair of supporting substructures 21, and the third pair of supporting structures 23 are located between the two second pair of supporting substructures 22. This invention implements the large pit in sections by setting the first pair of supporting structures 21, the second pair of supporting structures 22, and the third pair of supporting structures 23. Please refer to this document for details. Figures 3a to 3c It can quickly form a support system 20, reduce the length of the foundation pit, reduce its long side effect, and also allow for large-slope excavation, thus speeding up the construction process.

[0052] The first pair of support structures 21, the second pair of support structures 22 and the third pair of support structures 23 are provided with hydraulic cylinders 40 between the concrete walers 30 and the enclosure structure 10, and the hydraulic cylinders 40 are used for axial force compensation.

[0053] The construction method of this servo system includes the following steps:

[0054] Excavate the first layer of soil in the area where the first pair of support structures 21 are located, construct the first pair of support structures 21 and install the hydraulic cylinders 40, as follows. Figure 3a As shown;

[0055] Construction of the first-floor earthwork and supports in the area where the second pair of support structures 22 are located, and installation of the hydraulic cylinders 40, such as... Figure 3b As shown;

[0056] Construction includes the first-floor earthwork and support in the area where the third pair of support structures 23 are located, and the installation of the hydraulic cylinders 40, as follows. Figure 3c As shown;

[0057] After the first pair of support structures 21 are formed in the area where the first pair of support structures 21 are located, the excavation of the next layer of earthwork in the area where the first pair of support structures 21 are located begins.

[0058] After the second pair of support structures 22 are formed in the first layer of the area where the second pair of support structures 22 are located, the excavation of the next layer of earthwork in the area where the second pair of support structures 22 are located begins.

[0059] After the third pair of support structures 23 is formed in the first layer of the area where the third pair of support structures 23 is located, the excavation of the next layer of earthwork in the area where the third pair of support structures 23 is located begins.

[0060] Repeat the above construction procedures until all earthwork excavation is completed and the support system is formed.

[0061] This invention first forms a support and completes servo loading, then the lower layer of soil and support in the support area can be constructed, which speeds up the construction speed, reduces the soil exposure time, and thus effectively controls the deformation of the foundation pit adjacent to the protected object 01.

[0062] In some embodiments, the concrete of the bracing system 20 is early-strength concrete to improve the early strength of the concrete.

[0063] In some embodiments, please refer to the following: Figure 4 The hydraulic cylinders 40 are installed on the side of the foundation pit adjacent to the protected object 01. Each support is equipped with 3 hydraulic cylinders 40, and each hydraulic cylinder 40 is installed at the position where the support contacts the concrete waler 30.

[0064] In some embodiments, please refer to the following: Figure 4 and Figure 5 The hydraulic cylinder 40 is mounted on the concrete waler 30 via a support box 41, and its extended end contacts the embedded steel plate 44 at the end of the concrete support 24. When the hydraulic cylinder 40 extends, it can slide along the sliding layer 43 under the limiting action of the limiting block 42, providing active thrust for the concrete support 24. In some embodiments, a hanger 45 is also connected between the enclosure structure 10 and the concrete waler 30 to improve the stability of the support system 20.

[0065] In some embodiments, when the amount of separation between the concrete waler 30 and the retaining structure 10 is greater than δ, the gap is filled with high-strength mortar. The filling material is high-strength mortar. The filling is carried out before the lower layer of soil is excavated to prevent the concrete waler 30 from shrinking back after the hydraulic cylinder 40 fails, thereby affecting the safety of the foundation pit and the protected object 01.

[0066] In some embodiments, please refer to the following: Figure 6 A junction node 31 is provided at the connection between the concrete walers 30 of the substructures constructed first and later. The junction node 31 includes longitudinal reinforcement 32, connecting joints 33, the first substructure 34, and the later substructure 35. The connecting joints 33 are embedded at both ends of the first substructure 34. The connecting joints 33 at both ends are welded to the longitudinal reinforcement 32 of the first substructure 34 and the later substructure 35, respectively, so that the concrete walers 30 only transmit axial pressure and not bending moment, preventing cracking and damage to the support system caused by phased loading.

[0067] In some embodiments, please refer to the following: Figure 7The connecting joint 33 includes a mortise 51, a tenon 52, a first connecting member 53, and a second connecting member 54. The mortise 51 is fixed to the first connecting member 53, and the first connecting member 53 is connected to the pre-constructed substructure 34 / post-constructed substructure 35. The tenon 52 is fixed to the second connecting member 54, and the second connecting member 54 is connected to the post-constructed substructure 35 / pre-constructed substructure 34. The mortise 51 matches the tenon 52. During installation, the first connector 53 is first welded to the longitudinal reinforcement 32 of the substructure to be constructed first. Then, the mortise 51 is welded to the first connector 53 or connected with high-strength bolts. Next, the tenon 52 is inserted into the mortise 51. When the construction accuracy cannot be guaranteed, the tenon 52 is split into upper and lower parts and embedded into the mortise 51 respectively. Then, the tenon 52 is welded to the second connector 54 or connected with high-strength bolts. Finally, the second connector 54 is welded to the longitudinal reinforcement 32 of the substructure to be constructed later, thereby realizing the effective force transmission between the substructures 33 and 34 to be constructed first and later.

[0068] In some embodiments, please refer to the following: Figure 8 and Figure 9 The retaining structure 10 is also equipped with a pressure testing device 60 for measuring the active earth pressure on the side of the diaphragm wall. The pressure testing device 60 includes an optical fiber measuring line 61, an earth pressure sensor 62, a data acquisition and processing system 63, a flat steel bar 64, a rigid waterproof membrane 65, a limiting bar 66, and a ground wall reinforcement cage 67. The flat steel bar 64 is connected to the ground wall reinforcement cage 67 near the soil outside the pit in the diaphragm wall adjacent to the protected object 01 by the limiting bar 66. The optical fiber measuring line 61 and the earth pressure sensor 62 are arranged on the outside of the flat steel bar 64. After installation, the rigid waterproof membrane 65 is covered. When the diaphragm wall is trenched, it is placed into the soil together with the ground wall reinforcement cage 67. The signal detected by the earth pressure sensor 62 is transmitted to the data acquisition and processing system 63 through the optical fiber measuring line 61, thereby realizing the active earth pressure test on the side of the diaphragm wall.

[0069] In some embodiments, the method for loading the support system 20 further includes:

[0070] After the concrete construction of the supporting system 20 is completed, the concrete strength is tested. When the concrete strength reaches F... c0 Preloading begins when the concrete strength of the first pair of support structures 21 reaches F. c0 Apply hydraulic cylinder force to P0; the concrete strength of the second pair of support structures 22 reaches F. c0 Apply hydraulic cylinder force to P0; the concrete strength of the supporting structure of the third pair of support structures 23 reaches F. c0The hydraulic cylinder force is applied to P0. This invention employs the aforementioned servo force preloading method, which can compensate for concrete deformation caused by temperature and shrinkage, thereby achieving the effect of controlling early deformation of the foundation pit.

[0071] In some embodiments, when the concrete strength reaches F cn Apply servo force to lock value P n :

[0072] The concrete strength of the first pair of supporting structures 21 reaches F. cn Apply hydraulic cylinder force to the locked value P n ;

[0073] The concrete strength of the second pair of support structures 22 reaches F. cn Apply hydraulic cylinder force to the locked value P n ;

[0074] The concrete strength of the third pair of bracing structures 23 reaches F. cn Apply hydraulic cylinder force to the locked value P n The present invention employs the aforementioned servo force batch loading method, which can shorten the exposure time of the foundation pit soil, thereby achieving the effect of controlling the deformation of the foundation pit.

[0075] In some embodiments, the locking value P n The calculation methods include: P n =γ×p k ×L / n, where γ is the coefficient, p k Let L be the average confining pressure standard value, L be the length of the earth wall, and n be the number of hydraulic cylinders. When the axial force of hydraulic cylinder 40 is less than the support axial force, it means that the axial force of hydraulic cylinder 40 is insufficient to resist the support axial force; when the axial force of hydraulic cylinder 40 is equal to the support axial force, it means that the contribution of the axial force of hydraulic cylinder 40 to the active control of the support is 0. Therefore, to exert the active control function of hydraulic cylinder 40, the axial force of hydraulic cylinder 40 must be greater than the support axial force, that is, the γ value should not be less than 1.0. As the deformation of the earth wall increases, the axial force of hydraulic cylinder 40 is appropriately increased, and the alarm value is 1.1γ times the standard value of the support axial force. This invention can determine the batch loading method of servo force and the calculation method of servo force locking value, ensuring the stability and safety of foundation pit construction.

[0076] In some embodiments, the calculation of active earth pressure can also be added, when the average confining pressure standard value p of a certain support is determined. k When, its maximum value p k,max This refers to the horizontal force on the waler structure caused by the combined action of active and passive earth pressures during the excavation of the next support area but before the construction of the supporting structure. The average confining pressure standard value p is... k The calculation methods include:

[0077] Based on the measured values ​​of soil confining pressure obtained from the pressure testing device 60, a fitted regression surface equation F(x) is formed. n ,y n ,x n-1 ,y n-1 (x, y), where x is the length of the ground wall and y is the depth of the ground wall; the maximum confining pressure corresponding to the r-th single support is... The integral value; region Dr represents the range corresponding to a single support after the current support has been formed and excavation has reached the location of the next support, but before the next support has been formed. For example, if the total length of the diaphragm wall is L, the depth of the diaphragm wall is H, the depth of the third support is H1, the depth of the fourth support is H2, and the depth of the fifth support is H3, then region D4 in the y-direction is... The x-direction is from 0 to L. like Figure 10 As shown.

[0078] In summary, the construction method of the ultra-long foundation pit support servo system adjacent to the protected object provided by the present invention includes a retaining structure 10, a bracing system 20, a concrete waler 30, and a hydraulic cylinder 40. The bracing system 20 includes a first pair of bracing substructures 21, a second pair of bracing substructures 22, and a third pair of bracing substructures 23 separated along the length direction. The first pair of bracing substructures 21 are spaced apart, the second pair of bracing substructures 22 are located on both sides of the first pair of bracing substructures 21, and the third pair of bracing substructures 23 are located between the two second pair of bracing substructures 22. The hydraulic cylinder 40 is provided between the concrete waler 30 of the first pair of bracing substructures 21, the second pair of bracing substructures 22, and the third pair of bracing substructures 23 and the retaining structure 10. The construction method includes the following steps: excavating the first layer of soil in the area where the first pair of bracing substructures 21 are located, and constructing the first... The process involves: installing the hydraulic cylinder 40 on the support structure 21; constructing the first layer of earthwork and supports in the area where the second pair of support structures 22 are located, and installing the hydraulic cylinder 40; constructing the first layer of earthwork and supports in the area where the third pair of support structures 23 are located, and installing the hydraulic cylinder 40; after the first pair of support structures 21 are formed in the area where the first pair of support structures 21 are located, excavation of the next layer of earthwork in the area where the first pair of support structures 21 are located begins; after the second pair of support structures 22 are formed in the area where the second pair of support structures 22 are located, excavation of the next layer of earthwork in the area where the second pair of support structures 22 are located begins; after the third pair of support structures 23 are formed in the area where the third pair of support structures 23 are located, excavation of the next layer of earthwork in the area where the third pair of support structures 23 are located begins; repeating the above construction procedures until all earthwork excavation is completed and the support system is formed. This invention implements the large pit in sections by setting up a first pair of support structures 21, a second pair of support structures 22, and a third pair of support structures 23, quickly forming a support system 20, reducing the length of the foundation pit, reducing its long-side effect, and also allowing for large-slope excavation, thus accelerating the construction speed. Furthermore, this invention first forms the support and completes servo loading, then constructs the lower layer of soil and supports in the support area, accelerating the construction speed, reducing the soil exposure time, and thus effectively controlling the deformation of the foundation pit adjacent to the protected object 01.

[0079] Obviously, those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A construction method for a servo system for supporting an ultra-long foundation pit adjacent to a protected object, characterized in that, The system includes an enclosure structure, a bracing system, concrete walers, and hydraulic cylinders. The supporting system includes a first pair of supporting substructures, a second pair of supporting substructures, and a third pair of supporting substructures separated along the length direction. The first pair of supporting substructures are spaced apart, the second pair of supporting substructures are located on both sides of the first pair of supporting substructures, and the third pair of supporting substructures are located between the two second pair of supporting substructures. The hydraulic cylinders are provided between the concrete walers and the retaining structure of the first pair of support structures, the second pair of support structures and the third pair of support structures; The construction method includes the following steps: Excavate the first layer of soil in the area where the first pair of support structures are located, construct the first pair of support structures and install the hydraulic cylinders; Construction of the first-floor earthwork and supports in the area where the second pair of support structures are located, and installation of the hydraulic cylinders; Construction of the first-floor earthwork and supports in the area where the third pair of support structures are located, and installation of the hydraulic cylinders; After the first pair of support structures is formed in the area where the first pair of support structures are located, the excavation of the next layer of earthwork in the area where the first pair of support structures are located begins. After the second pair of support structures is formed in the first layer of the area where the second pair of support structures are located, the excavation of the next layer of earthwork in the area where the second pair of support structures are located begins. After the third pair of supports is formed in the area where the third pair of supports is located, the excavation of the next layer of earthwork in the area where the third pair of supports is located begins. Repeat the above construction procedures until all earthwork excavation is completed and the support system is formed.

2. The construction method as described in claim 1, characterized in that, The concrete used in the bracing system is early-strength concrete.

3. The construction method as described in claim 1, characterized in that, The hydraulic cylinder is mounted on the concrete waler via a support box, and its extended end contacts the embedded steel plate at the end of the concrete support. A sliding layer is provided below the hydraulic cylinder, and limit blocks are provided on both sides.

4. The construction method as described in claim 3, characterized in that, The retaining structure and the concrete waler are also connected by suspension bars.

5. The construction method as described in claim 1, characterized in that, A junction node is provided at the connection of the concrete waler between the substructures constructed first and later. The junction node includes longitudinal reinforcement, connecting joints, the substructure constructed first and the substructure constructed later. The connecting joints are embedded at both ends of the substructure constructed first, and the connecting joints at both ends are welded to the longitudinal reinforcement of the substructure constructed first and the substructure constructed later, respectively.

6. The construction method as described in claim 1, characterized in that, The retaining structure is also equipped with a pressure testing device for measuring the active earth pressure on the side of the diaphragm wall. The pressure testing device includes a fiber optic measuring line, an earth pressure sensor, a data acquisition and processing system, a flat steel bar, a non-rigid waterproof membrane, a limiting bar, and a ground wall reinforcement cage. The flat steel bar is connected to the ground wall reinforcement cage near the soil outside the pit in the diaphragm wall adjacent to the protected object. The fiber optic measuring line and earth pressure sensor are arranged on the outside of the flat steel bar. After installation, the non-rigid waterproof membrane is covered. The flat steel bar is placed into the soil together with the ground wall reinforcement cage when the diaphragm wall is excavated. The signal detected by the earth pressure sensor is transmitted to the data acquisition and processing system through the fiber optic measuring line.

7. The construction method as described in claim 1, characterized in that, It also includes methods for loading the support system, including: After the concrete construction of the supporting system is completed, the concrete strength is tested. When the concrete strength reaches F... c0 Preloading begins at this time: The concrete strength of the first pair of bracing structures reached F. c0 Apply hydraulic cylinder force to P0; The concrete strength of the second pair of bracing structures reaches F. c0 Apply hydraulic cylinder force to P0; The concrete strength of the third pair of bracing structures reaches F. c0 Apply hydraulic cylinder force to P0.

8. The construction method as described in claim 7, characterized in that, When the concrete strength reaches F cn Apply servo force to lock value P n : The concrete strength of the first pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n ; The concrete strength of the second pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n ; The concrete strength of the third pair of bracing structures reached F. cn Apply hydraulic cylinder force to the locked value P n .

9. The construction method as described in claim 8, characterized in that, The locking value P n The calculation methods include: P n =γ×p k ×L / n, where γ is the coefficient, p k The average confining pressure standard value is given, where L is the length of the ground wall and n is the number of hydraulic cylinders.

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