A force transmission retaining wall of a non-closed support system for a deep foundation pit and a construction method thereof

Abstract

This invention relates to the field of foundation pit support construction technology, and discloses a force-transfer retaining wall for a non-enclosed support system for deep foundation pits and its construction method. The method involves determining the area corresponding to the opening end of the non-enclosed support system on the deep pit side facing the shallow pit side in the adjacent area of ​​the deep and shallow pits. After layered excavation to the construction condition, the support bearing components and force-transfer retaining wall on the deep pit side are constructed, the reinforcement of the force-transfer retaining wall is tied, shear connectors are installed, a deformation release interface is reserved between the force-transfer retaining wall and the bearing components on the shallow pit side, and formwork installation, concrete pouring, and curing are carried out. Monitoring units are deployed in the area corresponding to the force-transfer retaining wall and the deformation release interface. Monitoring data is collected during subsequent construction, and construction parameters are adjusted when preset conditions are met. This scheme can establish a stable force transmission path in the adjacent area of ​​deep and shallow pits, reduce the adverse constraints of the deep pit side on the shallow pit side, and improve construction safety and efficiency.

Description

Technical Field

[0001] This invention relates to the field of foundation pit support, and more specifically to a force-transmitting retaining wall of a non-enclosed support system for deep foundation pits and its construction method. Background Technology

[0002] With the rapid development of urbanization and underground space construction, foundation pit support technology has been widely applied in the fields of building and municipal engineering. In actual engineering design, the layout of deep and shallow foundation pits adjacent to each other is increasingly common. This complex spatial relationship places higher demands on the design and construction of the foundation pit support system. In traditional deep-shallow pit adjacent support system schemes, the first support layer is usually uniformly arranged. Please combine... Figure 9 However, the second layer of corner bracing in deep pits often requires a large-scale second layer of bracing combined with a figure-eight bracing system at the adjacent shallow pit, or the installation of corner bracing with one end against the edge of the shallow pit floor, and cantilevered support piles at the shallow pit adjacent to the deep pit. However, this traditional support system has revealed significant shortcomings in practical applications. First, the large-scale bracing and its associated column piles involve a huge amount of work, leading to a significant increase in the overall cost of the support structure. Second, the complex support structure occupies a large amount of construction space, not only limiting the organization of large machinery such as pile foundations but also seriously affecting the efficiency of earthwork excavation, resulting in a prolonged construction period. Furthermore, if a corner bracing scheme against the shallow pit floor is adopted, the enormous water and soil pressure on the deep pit side can easily be transmitted to the shallow pit floor through the bracing, causing displacement or structural damage to the shallow pit floor, seriously interfering with the construction safety of the shallow pit's main structure. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a force-transmitting retaining wall and its construction method for a non-enclosed support system for deep foundation pits, thereby overcoming the aforementioned defects in existing technologies. The force-transmitting retaining wall described in this invention is suitable for foundation pit scenarios where the side support span of the deep pit is 30m to 70m and the boundary area between deep and shallow pits adopts cantilever or anchor-type large-span non-enclosed support. By setting a force-transmitting retaining wall perpendicular to the support direction, the large-span non-enclosed opening is transformed into in-plane rigid body force along the retaining wall direction.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for constructing a force-transfer retaining wall using a non-enclosed support system for deep foundation pits, including... In the adjacent area between the deep pit and the shallow pit, determine the area corresponding to the opening end of the non-enclosed support system on the deep pit side facing the shallow pit side, and complete the construction of the support components on the deep pit side, the support components on the shallow pit side, and the preceding support bearing components. The deep pit side and the shallow pit side are excavated in layers, so that the deep pit side is excavated to the construction elevation of the force transmission retaining wall and the deep pit side support and bearing components, and the shallow pit side is excavated to the corresponding foundation layer or bottom slab construction conditions. Construct a deep pit side support and bearing component in the area corresponding to the opening end, and tie the force transmission retaining wall reinforcement to form a connection between the force transmission retaining wall reinforcement and the deep pit side support and bearing component reinforcement. Connectors are installed between the force-transmitting retaining wall and the deep pit side support components, and a deformation release interface is reserved between the force-transmitting retaining wall and the shallow pit side support components. Install and fix the formwork on both sides of the force transmission retaining wall, and pour the force transmission retaining wall concrete and / or the deep pit side support bearing component concrete to form the force transmission retaining wall. After the force transmission retaining wall is formed, it is cured, and after the force transmission retaining wall and the side support components of the deep pit reach the predetermined strength, the subsequent excavation and structural construction continue. Monitoring units are deployed in the corresponding areas of the force-transmitting retaining wall and deformation release interface to collect monitoring data during subsequent construction. When the monitoring data meets the preset conditions, the subsequent construction parameters are adjusted.

[0005] In this invention, preferably, the reinforcement binding step of the force-transfer retaining wall includes first constructing the reinforcement of the deep pit side support bearing component, then inserting or binding the vertical reinforcement of the force-transfer retaining wall, and then binding the horizontal reinforcement and stirrups of the force-transfer retaining wall in sequence, so that the reinforcement of the force-transfer retaining wall is at least partially anchored into the deep pit side support bearing component, thereby forming an integral reinforcement skeleton between the force-transfer retaining wall and the deep pit side support bearing component.

[0006] In this invention, preferably, the deep pit side support receiving component is the deep pit side second support layer receiving component, and the force transmission retaining wall is used to receive the force transmitted to the adjacent area by the deep pit side second level support component, and forms the force transmission balance path of the deep pit side support system at the plane closing position.

[0007] In this invention, preferably, the shear connector is installed by welding, and during the binding of the force-transfer retaining wall reinforcement, the shear connector is welded to the deep pit side support member and / or the force-transfer retaining wall reinforcement, so as to complete the shear connection between the force-transfer retaining wall and the deep pit side support member before concrete pouring.

[0008] In this invention, preferably, the template installation includes installing side templates on both sides of the force-transfer retaining wall, setting template support components and tie members, and connecting and fixing at least part of the template support components to the deep pit side support components, so that the template system remains stable in position during the concrete pouring process of the force-transfer retaining wall.

[0009] In this invention, preferably, the pouring includes pouring the deep pit side support bearing component and the force transmission retaining wall together, or pouring the deep pit side support bearing component first and then pouring the force transmission retaining wall and connecting the two; after the pouring is completed, the concrete is cured, and after the concrete reaches the predetermined strength, the excavation continues in layers.

[0010] In this invention, preferably, the deformation release interface is formed by providing a compressible isolation element and / or reserving a gap between the force transmission retaining wall and the shallow pit side bearing member. The compressible isolation element is a wooden board, foam board, rubber board or other flexible isolation material, so as to allow relative deformation between the force transmission retaining wall and the shallow pit side bearing member, and reduce rigid constraints while transmitting support pressure.

[0011] In this invention, preferably, the wall strain monitoring unit is installed on the surface and / or internal stress area of ​​the force-transmitting retaining wall, the reinforcement stress monitoring unit is installed at the reinforcement of the force-transmitting retaining wall and / or the reinforcement of the deep pit side support bearing component, and the interface pressure monitoring unit is installed in the area corresponding to the deformation release interface; in the subsequent construction process, the data collected by the monitoring unit is compared with the monitoring value threshold, the rate of change threshold per unit time, the change trend judgment condition and / or the joint judgment condition of multiple monitoring indicators.

[0012] In this invention, preferably, when the monitoring data meets the preset conditions, the adjustment of subsequent construction parameters includes at least one of the following: adjusting the excavation sequence, adjusting the excavation method, adjusting the single-layer excavation thickness, adjusting the single excavation area, controlling the unloading rate of the adjacent area, prioritizing the construction of the subbase, prioritizing the construction of the base slab, prioritizing the construction of the replacement support structure, setting up temporary supports, taking local reinforcement measures, delaying the dismantling of supports, and adjusting the dismantling sequence of supports; wherein, when at least one of the monitoring data of wall strain, reinforcement stress, or interface pressure is abnormal, the excavation rate and excavation range of the adjacent area are controlled first.

[0013] A force-transmitting retaining wall in a non-enclosed support system for deep foundation pits, comprising: The force-transmitting retaining wall body is connected to the second support layer support component on the deep pit side to receive the force transmitted by the deep pit side support system. A shear-resistant connector is provided between the force-transmitting retaining wall body and the deep pit side support member, so that the force-transmitting retaining wall body and the deep pit side support member form a shear-resistant cooperation. Deformation release interface, which is set between the force transmission retaining wall body and the shallow pit side bearing component, to release the differential deformation between the deep pit and the shallow pit. A monitoring unit is installed at least at one location in the corresponding area of ​​the force transmission retaining wall body, the second support layer bearing component on the deep pit side, the bearing component on the shallow pit side, and the deformation release interface, for collecting strain, stress, pressure, or displacement data during the construction process.

[0014] The beneficial effects of this invention are: 1. This invention solves the core force transmission problem of non-enclosed support systems and avoids the inherent defects of traditional solutions. By setting a force-transmitting retaining wall in the adjacent area of ​​deep and shallow pits, this invention provides a rigid force-transmitting support for the horizontal corner support on the deep pit side. This solves the mechanical defects of out-of-plane buckling and mismatch of constraint stiffness in traditional retaining wall-less solutions. It allows the axial force of the deep pit side support to be effectively received and transmitted at the planar closing position of the non-enclosed support system, forming a continuous and stable force transmission path. At the same time, by setting a deformation release interface between the force-transmitting retaining wall and the shallow pit side support component, it takes into account both pressure transmission and differential deformation release, avoiding the direct rigid action of the deep pit side support reaction force on the shallow pit main structure or support structure, and significantly reducing the risk of deformation and structural damage on the shallow pit side.

[0015] 2. Significantly optimizes the economy and construction efficiency of support, freeing up working space. Compared with the traditional solution that uses a large number of braces, figure-eight braces and column piles, this invention completes the force transmission at the junction of adjacent areas through force-transfer retaining walls, which can significantly reduce the number of support components, reduce the overall cost of the support structure, and free up a lot of construction working space, making it easier to organize large machinery such as pile foundations, significantly improving earthwork excavation efficiency and shortening the construction cycle.

[0016] 3. The applicable working conditions and design boundaries are quantified, resulting in strong engineering applicability. This invention clarifies the optimal applicable span, stress range, and upper limit of bearing capacity design for force-transfer retaining walls, providing a clear quantitative basis for engineering design. It is not only applicable to scenarios where deep and shallow pits are adjacent, but can also be extended to adjacent connection areas between different excavation depths, different support levels, or different support forms, making it widely applicable.

[0017] 4. This invention achieves closed-loop information-based management and control throughout the entire construction process, enhancing construction safety. By deploying monitoring units in the force-transfer retaining wall and its adjacent key locations, the stress and deformation status of the adjacent areas can be monitored in real time, enabling early identification and graded control of risks. It goes beyond passive monitoring, directly using the monitoring results to guide subsequent construction. Through dynamic optimization of excavation sequence, excavation scale, support replacement timing, and base slab construction sequence, it achieves information-based construction and closed-loop risk control, significantly improving the safety and rationality of the construction process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the planar layout of the deep and shallow pit support system and the force-transfer retaining walls between them according to the present invention; Figure 2This is a detailed drawing of the plan layout and reinforcement of the force-transmitting retaining wall in this invention; Figure 3 This is a cross-sectional view of the force-transmitting retaining wall AA in this invention; Figure 4 This is the vertical BB section diagram and detailed drawing of the vertical stirrups of the force-transmitting retaining wall in this invention; Figure 5 This is an elevation view of the intelligent sensor arrangement on the force-transmitting retaining wall in this invention; Figure 6 This is a vertical planar force diagram of the force-transmitting retaining wall in this invention; Figure 7 This is a plan view of the force-transmitting retaining wall template in this invention; Figure 8 This is a CC cross-sectional view of the force-transmitting retaining wall template in this invention; Figure 9 It is a traditional deep and shallow pit adjacent support system scheme; Figure label: 1. Deep pit support piles; 1a. Deep pit support steel pipe piles; 1b. Larssen sheet piles; 2b. Second deep pit support; 2c. Second deep pit retaining beam; 3. Force transmission retaining wall; 3a. External reinforcement; 3b. Internal vertical reinforcement; 3c. Horizontal stirrups; 3d. Vertical stirrups; 4a. Shallow pit support piles; 4b. Shallow pit support beam; 5. Shear connection reinforcement; 6. Intelligent fiber optic strain sensor; 7. Intelligent steel reinforcement stress sensor; 7'. Intelligent retaining beam steel reinforcement stress sensor; 8. Intelligent pressure sensor; 9. Expansion joint; 10. Side formwork; 10a. Square timber joists; 10c. Steel pipe clamps; 10d. Welds; 10e. Fasteners; 14. Deep pit concrete cushion. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Please refer to Figures 1 to 8 This embodiment is applicable to engineering scenarios where deep foundation pits with two or more underground levels and shallow foundation pits with one underground level are adjacent to each other on a plane. Two or more support systems are installed on one side of the deep pit, and one support system is installed on the other side of the shallow pit. An open adjacent area of ​​the support system is formed on the deep pit side near the shallow pit. To address the issues of force balance at the end of the support system in this adjacent area, mutual interference between the deep and shallow pits, and dynamic risk control during construction, a force-transfer retaining wall is installed in the adjacent area of ​​the deep and shallow pits. A construction method based on real-time monitoring feedback is used to complete subsequent excavation and structural construction.

[0023] The core of this embodiment is to solve the problem of force transmission interruption in the non-enclosed support system of deep foundation pits, rather than a simple load-bearing problem. Its precise applicable working conditions and stress design boundaries are as follows: First, the force-transmitting retaining wall 3 described in this embodiment is suitable for foundation pit scenarios where the span of the side support of the deep pit is 30m≤L≤70m and the boundary area between the deep and shallow pits adopts the form of cantilever or anchor tension. By setting the force-transmitting retaining wall 3 perpendicular to the support direction, the large-span non-closed opening can be transformed into a plane rigid body force along the length of the retaining wall, thus solving the problem of force transmission balance at the opening end of the non-closed system.

[0024] Secondly, the simplified calculation diagram of the force-transmitting retaining wall 3 can be found in the appendix of the instruction manual. Figure 6 Its core bears the axial force N transmitted by the second support 2b of the deep pit; when the standard value of the axial force Nk generated by the water and soil pressure on the side of the deep pit is less than 100kN / m, it can be borne by the horizontal resistance of the deep pit support pile 1, and there is no need to set up this force transmission retaining wall; when the axial force is 100kN / m≤Nk≤300kN / m, it is the optimal applicable range of this embodiment. The in-plane stiffness of the retaining wall can be used to convert the line load into a surface load, which can be evenly transmitted to the side of the shallow pit through the deformation release interface, effectively protecting the main structure of the shallow pit.

[0025] In this embodiment, the force-transfer retaining wall 3 has a cross-sectional height h along the pit depth direction and a thickness b along the support axis, designed according to the pit depth and support axial force. Its ultimate bearing capacity is determined by the out-of-plane bending bearing capacity of the retaining wall and the shear bearing capacity of the shear connector. Taking a typical working condition with a support span of 60m and a remaining support axial force of 200kN / m after deducting the horizontal resistance of the support piles as an example, the upper limit of the shear bearing capacity of the force-transfer retaining wall is 12000kN, and the upper limit of the out-of-plane bending bearing capacity is 36000kN. m; if the height exceeds this limit, it is necessary to combine the reinforcement of the soil behind the wall or add buttress columns to solve the problem. This embodiment provides the optimal non-closed termination solution for deep foundation pit projects within this limit range.

[0026] In this embodiment, the deep pit side is provided with a deep pit side support component, a deep pit side first support layer receiving component, a deep pit side second support layer receiving component, and a deep pit side second-level support component; the shallow pit side is provided with a shallow pit side support component and a shallow pit side receiving component. The force-transmitting retaining wall is set at the plane termination position of the non-closed support system in the area adjacent to the deep pit and the shallow pit. Its lower part is connected to the deep pit side second support layer receiving component, and it is laterally connected to the deep pit side support component through a shear-resistant connector. A deformation release interface is set between the side facing the shallow pit and the shallow pit side receiving component, so that the deep pit side support reaction force can obtain a transmission path in the adjacent area while releasing the differential deformation between the deep and shallow pits.

[0027] In this embodiment, the deep pit side support components can be piles, steel pipe piles, steel sheet piles, diaphragm walls, or combinations thereof; preferably, a combination of steel pipe piles and steel sheet piles can be used to form the support system. The deep pit side second support layer bearing components can be reinforced concrete beams, steel walers, or combined walers; the shallow pit side bearing components can be shallow pit support beams or other components used to bear the support reaction force. The shear connection can be welded steel bars, anchors, connecting plates, studs, or mechanical connectors; the deformation release interface can be formed by wooden boards, foam boards, rubber boards, compressible isolation boards, elastic pads, or reserved gaps.

[0028] First, construction preparation and preliminary support construction are carried out. Based on the planar adjacency relationship between the deep pit and the shallow pit, the difference in excavation depth, the difference in the number of support layers, and the subsequent layout of the main structure, the planar termination position of the non-enclosed support system of the deep pit in the adjacent area is determined, and this position is designated as the force-transfer retaining wall construction area. This construction area is preferably located at the position where the second-level support member on the deep pit side and the supporting member on the shallow pit side are relatively adjacent, so as to form a shorter and more direct force transmission path.

[0029] Subsequently, the deep pit side support components and shallow pit side support components were constructed, and the construction of the first support layer bearing components on the deep pit side and the shallow pit side bearing components was completed. Once the above components reached the strength required for subsequent construction, the layered excavation and force-transfer retaining wall construction stage began.

[0030] In this embodiment, after the deep pit side support components are completed, the first support layer support components and corresponding support systems on the deep pit side are formed first; the shallow pit side support components and their support systems are also formed simultaneously or sequentially to ensure that the adjacent areas of deep and shallow pits have basic support conditions during subsequent construction.

[0031] After the support system is ready to bear loads, deep and shallow pits are excavated according to the principles of layering, zoning, and balanced unloading. The deep pit side is excavated layer by layer to near the construction elevation of the second support layer bearing the structural members and the force-transfer retaining wall; the shallow pit side is excavated layer by layer to near the construction conditions of its foundation layer or bottom slab, so as to ensure that the shallow pit side has the basic conditions to form a bearing constraint when the force-transfer retaining wall is set in the adjacent area.

[0032] This embodiment addresses the two inherent defects of traditional solutions that only involve horizontal corner supports without corresponding force-transfer retaining walls, fundamentally resolving these defects through a fundamental mechanical approach: First, there is the risk of out-of-plane buckling: the axial force direction of the side bracing of the deep pit, that is, the second support 2b of the deep pit, is usually at a non-orthogonal angle with the axis of the support beam 4b of the shallow pit. If the corner bracing is directly abutted against the waler of the shallow pit, the waler of the shallow pit will bear huge out-of-plane bending moment and shear force in addition to the axial force. The shallow pit side needs to be equipped with a closed support system to bear this additional load. Otherwise, its out-of-plane stiffness is too low and it is very easy to cause torsional instability failure.

[0033] Secondly, there is a mismatch in constraint stiffness: corner supports require fixed hinge supports to function properly, while shallow pit support piles 4a typically use cantilever support piles, which can only provide elastic foundation constraints; if a force-transfer retaining wall is missing, the horizontal displacement generated by the shallow pit side retaining structure during the deep pit excavation and unloading process will cause the axial force of the corner supports to decrease sharply, thus failing to effectively constrain the deformation of the deep pit sidewall, ultimately leading to excessive deformation of the deep pit sidewall.

[0034] Unlike traditional solutions that rely directly on bracing, herringbone bracing, or corner bracing against the edge of the shallow pit bottom, this embodiment reserves a construction area for force-transfer retaining walls during the excavation process. This allows the adjacent areas to form a force-transfer path through the retaining walls, rather than using large-scale lateral bracing that occupies construction space.

[0035] This embodiment constructs a complete mechanical model of the coordinated force distribution of the horizontal corner brace, waler, and force-transmitting retaining wall. The force characteristics and cooperative relationships of each component are as follows: In terms of the distribution of force among the components, the core function of the horizontal corner brace, also known as the second support 2b in the deep pit, is to bear the normal earth pressure transmitted from the sidewall of the deep pit and convert it into axial pressure along the direction of the members, thus solving the problem of lateral water and soil pressure balance inside the deep pit. The core function of the force-transmitting retaining wall 3 is to provide a rigid force-transmitting support for the horizontal corner brace at the opening end of the non-closed system, solving the problem of continuity of the force transmission path at the plane opening of the adjacent area. Without the force-transmitting retaining wall, the corner brace system would be a kinematic system or a constrained failure system at the opening end. The force-transmitting retaining wall is a rigid hinge and force-transmitting support at the plane turning point of the corner brace, and is a necessary mechanical component for the establishment of this combined support system.

[0036] This embodiment reconstructs the complete force transmission path in the adjacent area of ​​deep and shallow pits by setting up a force transmission retaining wall: deep pit side water pressure → deep pit support pile 1 → deep pit second retaining beam 2c → deep pit second support 2b (horizontal corner support / counterbraking) → force transmission retaining wall 3 → deformation release interface → shallow pit support retaining beam 4b → shallow pit support pile 4a.

[0037] In this force transmission path, the force-transmitting retaining wall 3 plays a crucial role in transforming the force distribution. First, it bears the axial pressure N by utilizing the large cross-sectional height of the retaining wall in the plane to diffuse the concentrated axial force of the corner support into a uniformly distributed load along the length of the retaining wall. Second, it resists the eccentric bending moment M by welding the shear connector to the deep pit side support component, converting the eccentric bending moment caused by the misalignment between the corner support's point of action and the retaining wall's centroid into a shear flow at the interface between the retaining wall and the support piles, ensuring that the retaining wall only bears in-plane pressure and does not overturn out of plane.

[0038] In this phase, it is preferable to control the single-layer excavation thickness and single-time excavation area in adjacent areas to avoid stress concentration in adjacent areas caused by excessively rapid local unloading on the deep pit side. This control requirement can serve as a construction organization principle and can also be adjusted in conjunction with subsequent monitoring results.

[0039] After the deep pit is excavated to the required elevation, the second support layer and the second-level support components on the deep pit side are constructed, and a force-transfer retaining wall is constructed in the adjacent area.

[0040] The force-transfer retaining wall is preferably constructed of reinforced concrete. During construction, the reinforcement skeleton of the force-transfer retaining wall is tied, the connectors are installed, and the formwork is erected first, and then concrete is poured to form the main body of the force-transfer retaining wall. The lower part of the main body of the force-transfer retaining wall is connected to the second support layer support member on the pit side, so that the axial force transmitted from the second-level support member on the pit side can be transmitted to the force-transfer retaining wall through the second support layer support member; the main body of the force-transfer retaining wall is laterally connected to the support member on the pit side through shear connectors, so that when the force-transfer retaining wall is subjected to the overturning tendency caused by the difference in axial force, the shear connectors and contact surfaces can work together to resist the rotational torque generated by eccentric force.

[0041] Preferably, the force-transfer retaining wall can also form a collaborative relationship with the upper support and bearing components on the side of the deep pit through vertical connecting steel bars, support components or other connection means, thereby connecting different support levels of the deep pit into a whole in the adjacent area, so that the non-closed support system can achieve stable closing at the plane opening.

[0042] On the side of the force-transmitting retaining wall facing the shallow pit, a deformation release interface is provided between it and the supporting components on the shallow pit side. The deformation release interface is not required to form a rigid integral connection, but is allowed to absorb a certain displacement difference and rotation difference while transmitting pressure, so as to reduce the adverse effects of the direct rigid action of the deep pit side support reaction force on the shallow pit side support system or main structure.

[0043] In this embodiment, the deformation release interface can be formed using a compressible isolation plate of predetermined thickness; preferably, the thickness of the isolation plate can be set according to design requirements, for example, in the range of several millimeters to several centimeters. More preferably, the interface material can be selected from wood-based panels, foam boards, rubber boards, polymer elastic boards, or other compressible materials depending on the engineering environment.

[0044] To enable information feedback during subsequent construction, monitoring units are installed at the force-transfer retaining wall and its adjacent key locations. Each monitoring unit includes at least one of the following: a wall strain monitoring unit, a reinforcement stress monitoring unit, an interface pressure monitoring unit, a waler stress monitoring unit, and a displacement monitoring unit.

[0045] The wall strain monitoring unit is preferably installed on the outer surface or in key stress areas of the retaining wall to monitor the surface strain, tensile and compressive strain, or bending deformation trend of the retaining wall under the reaction force of the deep pit side support. This monitoring unit can employ intelligent fiber optic strain sensors, strain gauges, distributed strain monitoring elements, or other strain sensing devices. The reinforcement stress monitoring unit is preferably installed at the main reinforcement of the retaining wall, the main reinforcement of the second support layer on the deep pit side, and, if necessary, the main reinforcement of the upper support layer, to monitor the stress changes of the reinforcement in real time. This monitoring unit can employ rebar gauges, stress gauges, or other monitoring devices that can reflect the stress state of the reinforcement. The interface pressure monitoring unit is preferably installed in the contact area between the retaining wall and the shallow pit side support component to sense the changes in contact pressure between the two in real time. When the support force transmission state of the adjacent area changes abruptly, the interface pressure monitoring unit can reflect the local stress redistribution earlier. The waler stress monitoring unit can be installed in the second support layer support component on the deep pit side and the shallow pit side support component to assist in judging the stress changes of the overall support system in the adjacent area. Displacement monitoring units can be deployed on force-transmitting retaining walls, support components, or adjacent ground surfaces and enclosures as needed for engineering projects, to supplement and reflect the overall deformation.

[0046] Each monitoring unit is preferably connected to a wireless acquisition node, a wired acquisition node, or a hybrid transmission node, and transmits the data to the monitoring and processing module for subsequent construction judgment and adjustment.

[0047] After the force-transfer retaining wall construction is completed and reaches the predetermined strength, the subsequent construction of the deep pit and shallow pit continues, including the continued layered excavation, construction of the foundation layer, construction of the shallow pit bottom slab, formation of the replacement support structure, and continued excavation towards the bottom of the deep pit.

[0048] During the construction process, data from each monitoring unit is continuously collected, and the monitoring data is compared with preset thresholds, rate of change thresholds, or trend judgment rules to identify whether there are risk states such as stress imbalance, local stress concentration, abnormal support reaction force, sudden change in interface pressure, or abnormal structural deformation in adjacent areas.

[0049] In this embodiment, the determination rule may include any one or a combination of the following: Firstly, when the wall strain monitoring value exceeds the wall strain early warning threshold, or the strain change rate per unit time exceeds the preset rate threshold, it is determined that the stress state of the force transmission retaining wall has changed significantly, and the adjacent area enters the key control state. Secondly, when the reinforcement stress monitoring value is close to or exceeds the reinforcement stress warning threshold, it is determined that the load-bearing component of the force transmission retaining wall or the second support layer on the side of the deep pit may have local bearing risk or stress concentration. Third, when the interface pressure monitoring value shows an abnormal sudden increase, sudden decrease, or fluctuation exceeding the limit, it is determined that the deep pit side support reaction force is unstable in the adjacent area, and there is a risk of local imbalance. Fourth, when multiple monitoring parameters show abnormal trends simultaneously, the adjacent area is determined to enter a comprehensive early warning state, and the subsequent construction control level is upgraded.

[0050] Preferably, the determination can be based on a single indicator or on a combination of multiple indicators, such as combining three types of data: wall strain, steel stress, and interface pressure, to improve the accuracy of the early warning.

[0051] When the monitoring and processing module determines that a certain monitoring indicator or multiple monitoring indicators have reached the preset adjustment conditions, it dynamically optimizes the subsequent construction content.

[0052] In a preferred embodiment, when the wall strain monitoring value increases abnormally, the earthwork excavation rate in the adjacent area is reduced, and the single excavation area in that area is reduced; if necessary, the bottom slab, cushion layer, and replacement support strip in the shallow pit side or adjacent area are constructed first to form a constraint system as soon as possible, thereby reducing the duration of the free stress stage of the force transmission retaining wall.

[0053] In another preferred embodiment, when the reinforcement stress monitoring value is close to the warning threshold, the excavation sequence is adjusted. It is preferred to adopt the side span priority excavation, zone alternating excavation or skip-section excavation method to avoid excessively rapid unloading in a certain local area. If necessary, temporary reinforcement measures are taken for the force transmission retaining wall, the second support layer bearing component or support component on the deep pit side.

[0054] In another preferred embodiment, when the interface pressure monitoring value changes abruptly, the single excavation depth and single excavation range are controlled to delay the continued unloading of the corresponding area, and key monitoring is carried out on the components near the deformation release interface; if necessary, the dismantling of supports is delayed or the dismantling sequence is adjusted to avoid prematurely removing the support constraints during the unstable interface pressure stage.

[0055] Preferably, the dynamic optimization includes, but is not limited to, one or more of the following: adjusting the excavation sequence, adjusting the single-layer excavation thickness, adjusting the single-excavation area, adopting alternating zone excavation, adopting skip-section excavation, prioritizing the formation of cushion layer constraints, prioritizing the formation of bottom plate constraints, constructing replacement support strips in advance, setting up temporary supports, reinforcing local components, delaying the removal of supports, and adjusting the removal sequence of supports.

[0056] Through the above dynamic optimization method, this embodiment no longer relies solely on construction experience for judgment, but rather corrects the construction plan based on the real-time stress state of the force-transmitting retaining wall and adjacent areas, thereby achieving information-based construction and closed-loop risk control.

[0057] Under monitoring and control, subsequent construction on the shallow pit side and the deep pit side continues. Preferably, the foundation layer and bottom slab are constructed first on the shallow pit side, or a replacement support zone is formed first on the shallow pit side, so as to form a restraining effect on the adjacent area as early as possible; then, the downward excavation on the deep pit side is completed, and the foundation layer, bottom slab and replacement support structure on the deep pit side are constructed after the design elevation is reached.

[0058] Once the shallow pit floor slab, deep pit floor slab, and corresponding support structures have reached their predetermined strength and can provide reliable support, the second-level support components on the deep pit side, the second support layer bearing components on the deep pit side, the force-transfer retaining wall, and the bearing components on the shallow pit side will be gradually dismantled or partially dismantled. During the dismantling process, some monitoring units can still be retained to monitor key areas to prevent secondary stress concentration during the dismantling phase.

[0059] In implementations requiring the removal of the force-transfer retaining wall, the shear connection between the retaining wall and the pit side support components can be disconnected first, followed by the removal of the retaining wall and subsequent construction of the basement exterior walls. The support components can be further removed, retained, or converted into part of the permanent structure, depending on the engineering plan.

[0060] In this embodiment, for ease of understanding of the force-transmitting retaining wall structure designed in this application, please refer to the accompanying drawings. In this application, the second-level support component on the deep pit side is specifically the second support 2b of the deep pit, the supporting component of the second support layer on the deep pit side is specifically the second retaining beam 2c of the deep pit, the supporting component on the shallow pit side is specifically the retaining beam 4b of the shallow pit support, the shear connection component is specifically the shear connection bar 5, the deformation release interface is specifically the expansion joint 9, the wall strain monitoring unit specifically adopts the intelligent fiber optic strain sensor 6, the reinforcement stress monitoring unit adopts the intelligent steel bar stress sensor 7, and the interface pressure monitoring unit adopts the intelligent pressure sensor 8.

[0061] Working principle: For a detailed calculation diagram of the vertical plane force on the force-transmitting retaining wall in this embodiment, please refer to the appendix of the instruction manual. Figure 6 Its core design logic is to transform the concentrated axial force of the non-closed support system on the deep pit side into a uniformly distributed surface force by utilizing the in-plane rigidity of the retaining wall. At the same time, the deformation release interface takes into account both pressure transmission and differential deformation release, avoiding the direct rigid action of the support reaction force on the deep pit side on the shallow pit structure. The shear-resistant connector solves the overturning problem of the retaining wall under eccentric force, forming a complete self-balancing force system.

[0062] The construction method for the force-transfer retaining wall of the non-enclosed support system for deep foundation pits involved in this application can be referred to as follows according to the complete construction process: 1) After the deep pit support pile 1, shallow pit support pile 4a, deep pit first support beam and shallow pit support beam 4b are all completed and reach the design strength, the deep pit is excavated in layers to the bottom of the deep pit concrete cushion 14 of the deep pit second support beam 2c, with a preset elevation of -4.40m. The shallow pit is excavated in layers to the bottom of the bottom slab cushion and the shallow pit concrete cushion is constructed immediately.

[0063] 2) Fabricate and process various steel bars and formwork systems for the second support 2b and the second retaining beam 2c of the deep pit and the force transmission retaining wall 3 according to the design. The side formwork 10 and the square timber joists 10a are fixed with iron nails.

[0064] 3) Construct the second support 2b and the second retaining beam 2c of the deep pit, insert the outer reinforcement 3a, inner vertical reinforcement 3b, and vertical stirrup 3d of the force transmission retaining wall 3, and install the shear connection reinforcement 5. Finally, pour commercial concrete to construct the second support 2b and the second retaining beam 2c of the deep pit, and keep them moist for curing.

[0065] 4) The process flow for tying the reinforcing bars of the force-transfer retaining wall 3 is as follows: insert the vertical section of the outer reinforcing bar 3a → insert the inner vertical reinforcing bar 3b → tie the horizontal section of the outer reinforcing bar 3a → tie the horizontal stirrups 3c → tie the vertical stirrups 3d → install the shear connecting bar 5 and weld it to the Larssen sheet pile 1b → acceptance of concealed works. The above-mentioned reinforcement tying of the force-transfer retaining wall 3 is carried out in accordance with the design requirements.

[0066] 5) Install various intelligent sensors: intelligent fiber optic strain sensor 6, intelligent steel bar stress sensor 7, intelligent pressure sensor 8, and intelligent beam steel bar stress sensor 7'.

[0067] The intelligent fiber optic strain sensor body 6a is bonded to the outer surface of the retaining wall 3 via a concrete fiber cloth 6b. It is connected to a wireless acquisition node via a wire 6c to measure the surface strain distribution of the retaining wall 3 under external loads in real time. The intelligent fiber optic strain sensor 6 can capture the bending, tensile, or compressive deformation trends of the retaining wall 3, and is particularly sensitive to areas of localized stress concentration. It can provide direct evidence for judging changes in the overall stiffness of the retaining wall 3 and the risk of crack propagation. During earthwork excavation, abrupt changes in the intelligent fiber optic strain sensor 6 often indicate changes in the stress state of the retaining wall 3, requiring comprehensive evaluation in conjunction with other monitoring data.

[0068] The steel reinforcement stress sensor body 7a is welded to the main reinforcing bars on both sides of the force-transmitting retaining wall 3 and the main reinforcing bars on both sides of the second retaining beam 2c in the deep pit via the guide rod 7b. It is connected to a wireless acquisition node via the wire 7c to measure the actual stress values ​​of the force-transmitting retaining wall 3 and the second retaining beam 2c in the deep pit in real time. The internal forces of the concrete structure and the axial forces of the retaining beam can be calculated from the steel reinforcement stress. The intelligent steel reinforcement stress sensor 7 directly reflects the stress level of the steel reinforcement in key stress-bearing parts of the structure and is a core indicator for determining whether the force-transmitting retaining wall 3 and the second retaining beam 2c in the deep pit are in an elastic working state and whether they exceed limits. When the steel reinforcement stress approaches or exceeds the warning value, it indicates that the structure may have insufficient bearing capacity, requiring immediate adjustment of the excavation sequence or reinforcement of the support structure.

[0069] The pressure box 8b of the intelligent pressure sensor 8 is embedded at the contact surface between the force transmission retaining wall 3 and the shallow pit support beam 4b. The cross-section of the pressure box 8b is either circular or rectangular. The pressure box 8b is connected to the fiber optic pressure sensor body 8a via an oil pipe 8c and to a wireless acquisition node via a wire 8d, reflecting the changes in the contact axial force N' between the force transmission retaining wall 3 and the shallow pit support beam 4b in real time. When the contact axial force N' changes abruptly, it may indicate an imbalance of unbalanced forces in the opening area of ​​the second support 2b in the deep pit. It is necessary to control the excavation progress to prevent pressure concentration from causing instability of the support structure.

[0070] 6) Erect the side formwork 10, along with the square timber joists 10a, steel pipe clamps 10c, and side formwork tie bolts 10b. Drill holes in advance at the designed positions for the deep pit support steel pipe piles 1a and deep pit Larssen steel sheet piles 1b to allow the tie bolts 10b to pass through the side formwork. Weld the steel pipe clamps 10c at both ends of the force transmission retaining wall 3 to the deep pit support steel pipe piles 1a at the erection location to form weld seams 10d. Finally, fix each longitudinal and transverse steel pipe clamp 10c with fasteners 10e. Use a 10mm thick plate to isolate the force transmission retaining wall 3 from the shallow pit support beam 4b, forming an expansion joint 9.

[0071] 7) The concrete 3e of the force transmission retaining wall 3 is poured in layers using commercial concrete and an immersion vibrator, and then moisturized and cured.

[0072] 8) After the concrete 3e of the force transmission retaining wall 3 is poured, the side formwork 10 is removed after the concrete of the second support 2b and the second retaining beam 2c of the deep pit and the force transmission retaining wall 3 is poured. The deep and shallow foundation pits can continue to be excavated in layers only after the concrete reaches 80% of the design strength.

[0073] 9) Based on the sensing information of various intelligent sensors arranged on the force transmission retaining wall 3, such as intelligent fiber optic strain sensor 6, intelligent steel bar stress sensor 7, intelligent pressure sensor 8, and intelligent retaining beam steel bar stress sensor 7', the excavation procedures and measures for deep and shallow pits are adjusted in real time, or the supports and retaining beams are reinforced.

[0074] 10) Continue excavating in layers to the bottom elevation of the shallow pit foundation, and immediately construct the shallow pit concrete foundation, shallow pit bottom slab, and replacement support strip. Continue excavating in layers for the deep pit to the bottom elevation of the deep pit foundation, and immediately construct the deep pit concrete foundation 14, deep pit bottom slab, and replacement support strip.

[0075] 11) Once the concrete of the deep pit bottom slab and the replacement support strip, and the shallow pit bottom slab and the replacement support strip, reaches the design strength, the second support 2b of the deep pit, the second retaining beam 2c of the deep pit, the force transmission retaining wall 3, and the support beam 4b of the shallow pit can be removed. The removal work shall be carried out in accordance with the design requirements.

[0076] When dismantling the force transmission retaining wall 3, cut off the shear connecting bar 5 that is welded to the deep pit Larssen steel sheet pile 1b in the deep pit support pile 1. Construct the basement concrete exterior wall, remove the deep pit support steel pipe pile 1a and Larssen steel sheet pile 1b and the shallow pit support pile 4a, and finally backfill the foundation pit trench in layers.

[0077] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A construction method of a force transfer wall of a non-enclosed support system of a deep foundation pit, characterized in that, include In the adjacent area between the deep pit and the shallow pit, determine the area corresponding to the opening end of the non-enclosed support system on the deep pit side facing the shallow pit side, and complete the construction of the support components on the deep pit side, the support components on the shallow pit side, and the preceding support bearing components. The deep pit side and the shallow pit side are excavated in layers, so that the deep pit side is excavated to the construction elevation of the force transmission retaining wall and the deep pit side support and bearing components, and the shallow pit side is excavated to the corresponding foundation layer or bottom slab construction conditions. Construct a deep pit side support and bearing component in the area corresponding to the opening end, and tie the force transmission retaining wall reinforcement to form a connection between the force transmission retaining wall reinforcement and the deep pit side support and bearing component reinforcement. During the reinforcement binding process of the force transmission retaining wall, shear connectors are installed between the force transmission retaining wall and the deep pit side support components, and a deformation release interface is reserved between the force transmission retaining wall and the shallow pit side support components. Install and fix the formwork on both sides of the force transmission retaining wall, and pour the force transmission retaining wall concrete and / or the deep pit side support bearing component concrete to form the force transmission retaining wall. After the force transmission retaining wall is formed, it is cured, and after the force transmission retaining wall and the side support components of the deep pit reach the predetermined strength, the subsequent excavation and structural construction continue. Monitoring units are deployed in the corresponding areas of the force-transmitting retaining wall and deformation release interface to collect monitoring data during subsequent construction. When the monitoring data meets the preset conditions, the subsequent construction parameters are adjusted; The force-transmitting retaining wall is located at the plane termination position of the non-enclosed support system in the area adjacent to the deep pit and the shallow pit. Its lower part is connected to the second support layer bearing member on the deep pit side, and it is laterally connected to the support member on the deep pit side through shear-resistant connectors. A deformation release interface is set between the side facing the shallow pit and the bearing member on the shallow pit side, so that the support reaction force on the deep pit side can obtain a transmission path in the adjacent area while releasing the differential deformation between the deep and shallow pits.

2. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The reinforcement binding steps of the force-transfer retaining wall include first constructing the reinforcement of the deep pit side support bearing component, then inserting or binding the vertical reinforcement of the force-transfer retaining wall, and then binding the horizontal reinforcement and stirrups of the force-transfer retaining wall in sequence, so that the reinforcement of the force-transfer retaining wall is at least partially anchored into the deep pit side support bearing component, thereby forming an integral reinforcement skeleton between the force-transfer retaining wall and the deep pit side support bearing component.

3. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The deep pit side support receiving component is the second support layer receiving component on the deep pit side. The force transmission retaining wall is used to receive the force transmitted to the adjacent area by the second level support component on the deep pit side, and forms a force transmission balance path of the deep pit side support system at the plane closing position. The plane closing position is located in the adjacent area between the deep pit and the shallow pit.

4. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 3, characterized in that, The shear connector is installed by welding, and during the binding of the retaining wall reinforcement, the shear connector is welded to the deep pit side support member and / or the retaining wall reinforcement, so as to complete the shear connection between the retaining wall and the deep pit side support member before the concrete is poured.

5. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The template installation includes installing side templates on both sides of the force-transfer retaining wall, setting template support components and tie members, and connecting and fixing at least some of the template support components to the deep pit side support components, so that the template system remains stable in position during the concrete pouring process of the force-transfer retaining wall.

6. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The pouring process includes pouring the deep pit side support and bearing components together with the force transmission retaining wall, or pouring the deep pit side support and bearing components first and then pouring the force transmission retaining wall and connecting the two; after the pouring is completed, the concrete is cured and excavation continues in layers after the concrete reaches the predetermined strength.

7. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The deformation release interface is formed by setting a compressible isolation element and / or reserving a gap between the force transmission retaining wall and the shallow pit side bearing component.

8. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 1, characterized in that, The monitoring unit includes at least one of the following: wall strain monitoring unit, reinforcement stress monitoring unit, interface pressure monitoring unit, waler stress monitoring unit, and displacement monitoring unit.

9. The construction method for the force-transmitting retaining wall of the non-enclosed support system for deep foundation pits according to claim 8, characterized in that, When the monitoring data meets the preset conditions, the adjustment of subsequent construction parameters includes at least one of the following: adjusting the excavation sequence, adjusting the excavation method, adjusting the single-layer excavation thickness, adjusting the single excavation area, controlling the unloading rate of the adjacent area, prioritizing the construction of the subbase, prioritizing the construction of the base slab, prioritizing the construction of the replacement support structure, setting up temporary supports, taking local reinforcement measures, delaying the dismantling of supports, and adjusting the dismantling sequence of supports; wherein, when at least one of the monitoring data of wall strain, reinforcement stress, or interface pressure is abnormal, the excavation rate and excavation range of the adjacent area are controlled first.

10. A force-transmitting retaining wall for a non-enclosed support system for deep foundation pits, constructed using the force-transmitting retaining wall construction method for a non-enclosed support system for deep foundation pits as described in any one of claims 1-9, characterized in that... include: The force-transmitting retaining wall body is connected to the second support layer support component on the deep pit side to receive the force transmitted by the deep pit side support system. A shear-resistant connector is provided between the force-transmitting retaining wall body and the deep pit side support member, so that the force-transmitting retaining wall body and the deep pit side support member form a shear-resistant cooperation. Deformation release interface, which is set between the force transmission retaining wall body and the shallow pit side bearing component, to release the differential deformation between the deep pit and the shallow pit. A monitoring unit is installed at least at one location in the corresponding area of ​​the force transmission retaining wall body, the second support layer bearing component on the deep pit side, the bearing component on the shallow pit side, and the deformation release interface, for collecting strain, stress, pressure, or displacement data during the construction process.

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