Prestress servo supporting system for supporting and loading before excavation of foundation pit and construction method

Abstract

According to the prestress servo supporting system for supporting and loading before foundation pit excavation and the construction method, a transverse supporting mechanism is provided with a supporting rod piece, one end of the supporting rod piece abuts against the inner wall of one side of an enclosure structure, and the other end of the supporting rod piece is provided with a limiting mechanism and loading equipment; and a counter-force frame is detachably mounted at the other end of the supporting rod piece. Transverse loading force can be temporarily provided by means of the counter-force frame, in the process that the counter-force frame provides transverse jacking force, the loading force of the loading equipment can be unloaded, the loading equipment is installed at a preset position after a weak intercalated layer on the surface of the embedded part base plate is cleaned up, then the loading equipment applies the transverse loading force again, and the loading equipment can be used for loading the embedded part base plate. The loading force applied by the loading equipment can directly act on the embedded part base plate of the enclosure mechanism, it is guaranteed that the force can be accurately applied in the magnitude and direction, and the situation that transmission of the transverse loading force is affected by a weak intercalated layer originally existing in a loading area is avoided.

Description

Technical Field

[0001] The invention relates to foundation pit construction, and in particular to a prestressed servo support system for supporting and loading before foundation pit excavation and a construction method. Background Art

[0002] In the current underground structure construction process, ensuring the safety of the foundation pit and its surrounding environment is a vital task. In order to achieve this goal, effective support, reinforcement and protection measures must be taken on the side walls of the foundation pit. In existing construction technology, the support system of the foundation pit is usually gradually erected and installed after the earthwork is excavated to a predetermined depth or elevation to form a series of reliable fulcrums. However, during the earthwork excavation process, since a stable fulcrum has not yet been formed in the next support or bottom plate area, the rheological phenomenon of the surrounding soil will cause a large deformation of the retaining structure. This deformation not only affects the stability of the foundation pit, but may also pose a potential threat to surrounding buildings, underground pipelines and other important facilities.

[0003] In view of this, there is an urgent need to develop a more advanced support system and construction method to achieve more effective protection of the environment around the foundation pit. Summary of the invention

[0004] The present invention provides a prestressed servo support system and construction method for supporting and loading before foundation pit excavation, which can provide sufficient support force in the early stage of earth excavation, thereby significantly reducing the deformation degree of the surrounding structure during earth excavation. In this way, the protection of the surrounding environment can be further enhanced, and the safety and stability during the construction process can be ensured. This not only helps to improve construction efficiency, but also reduces the additional repair costs caused by excessive deformation, thereby bringing significant benefits both economically and technically. In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0005] A prestressed servo support system for supporting and loading before foundation pit excavation, the prestressed servo support system comprising a plurality of lateral support mechanisms sequentially distributed in parallel along the height direction of the foundation pit;

[0006] The lateral support mechanism is provided with a support rod, one end of which abuts against the inner wall of one side of the enclosure structure, and the other end of which is provided with a limiting mechanism and a loading device, wherein the loading device is provided with a loading end for abutting against the inner wall of the other side of the enclosure structure;

[0007] A reaction frame is detachably mounted on the other end of the support rod, the reaction frame abuts between the limiting mechanism and the inner wall on the other side of the enclosure structure, the rear end of the reaction frame abuts on the limiting mechanism, and the front end of the reaction frame is provided with a reaction loading mechanism for abutting against the inner wall on the other side of the enclosure structure.

[0008] Furthermore, a plurality of groups of transverse support mechanisms are arranged in the horizontal direction in the enclosure structure, and each group of transverse support mechanisms is provided with a plurality of transverse support mechanisms sequentially distributed in parallel along the height direction of the foundation pit;

[0009] A plurality of preformed trenches are distributed at intervals in the original soil within the area enclosed by the enclosure structure. The preformed trenches are provided with mud walls, at least one set of transverse support mechanisms are provided in the preformed trenches, and columns are also provided in the original soil between adjacent preformed trenches.

[0010] Furthermore, the end surface of the loading end facing the inner wall of the enclosure structure is provided with a plurality of water spraying ports, a channel connected to the water spraying ports is provided inside the loading end, and a water injection port connected to the channel is provided on the surface of the loading end;

[0011] Each of the lateral supporting mechanisms is provided with a cleaning mechanism, and the cleaning mechanism comprises a water pipe connected to the water injection port, and the other end of the water pipe is connected to a water pump.

[0012] Furthermore, the support rod is a steel pipe, a steel section or a precast concrete pile, and the limiting mechanism is a convex ring or a stopper provided on the outer wall of the support rod;

[0013] A rubber corrugated telescopic tube is sleeved on the outer surface of the loading device.

[0014] Furthermore, the loading device is detachably connected to the supporting rod;

[0015] The loading device and / or the reaction force loading mechanism is a jack.

[0016] Furthermore, the reaction frame is provided with a plurality of reaction blocks which are symmetrical about the center of the support rod, the support rod is clamped in the middle of the plurality of reaction blocks, and the plurality of reaction blocks are fixedly connected and installed on the support rod by bolts.

[0017] Furthermore, the inner wall of the enclosure structure is provided with an embedded pad for cooperating with the loading device and the reaction force loading mechanism.

[0018] A construction method based on the above-mentioned prestressed servo support system, the method comprising the following steps:

[0019] S1. Construct the enclosure structure outside the foundation pit to be formed.

[0020] S2, excavating the original soil in the retaining structure to form a pre-formed trench, wherein the pre-formed trench is protected by mud walls;

[0021] S3, lowering a plurality of the lateral support mechanisms installed with the loading device but not installed with the reaction frame into the prefabricated groove;

[0022] S4, applying initial prestress to the enclosure structure using the loading device;

[0023] S5. Carry out earth excavation to the predetermined elevation.

[0024] S6, fixing the reaction frame on the support rod, and applying a loading force to the inner wall of the enclosure structure by using the reaction loading mechanism;

[0025] S7, canceling the prestress applied by the loading device, and cleaning the inner wall of the enclosure structure in the force application area of ​​the loading device to clean the weak interlayer on the inner wall surface of the enclosure structure in the prestress loading area;

[0026] S8, the loading device is loaded to an initial prestress, and then continues loading until the prestress requirement is reached;

[0027] S9, canceling the loading force applied by the reaction force loading mechanism and removing the reaction force frame;

[0028] S10, excavating the earth layer by layer, and performing steps S6 to S9 once each time the next layer is excavated to a specified height.

[0029] Furthermore, the loading device drives the loading end head to retract so as to cancel the prestress applied by the loading device.

[0030] Furthermore, after the loading device drives the loading end head to retract, the loading device is removed to cancel the prestress applied by the loading device; and

[0031] In step S8, the disassembled loading device is installed back on the supporting rod, and then stress loading is performed.

[0032] Furthermore, in step S4, before applying the initial prestress, the following steps are also included:

[0033] The inner wall of the enclosure structure in the force application area of ​​the loading device is pre-cleaned by spraying water with the loading end head to flush away the sludge attached to the inner wall of the enclosure structure.

[0034] Furthermore, in step S1, several rows of columns are inserted into the original soil in the enclosure structure.

[0035] The preformed groove is arranged between adjacent columns.

[0036] Further, in step S3, the plurality of lateral support mechanisms without the reaction frame installed are first connected in series up and down in sequence through steel strands, and then the lateral support mechanisms connected in series are connected to a lifting device through steel strands, and the lateral support mechanisms connected in series are lowered as a whole into the prefabricated groove through the lifting device;

[0037] In step S4, after the loading device applies the initial prestress, the following steps are also included:

[0038] Remove all the steel strands and keep the transverse support mechanism in the preformed groove, or

[0039] The steel strands used for lifting are removed and the transverse supporting mechanisms and the steel strands connected between the transverse supporting mechanisms are retained in the preformed grooves.

[0040] Furthermore, in step S3, the lateral support mechanism installed with the loading device and not installed with the reaction frame is lowered into the prefabricated groove one by one from bottom to top by using a steel strand through a lifting device;

[0041] In step S4, after the loading device applies the initial prestress, the following step is also included: removing the steel strands and retaining the transverse support mechanism in the preformed groove.

[0042] The advantages of the present invention are:

[0043] 1. The prestressed servo support system can effectively control the displacement of soil during foundation pit excavation and reduce the impact on surrounding buildings and underground pipelines. The implementation of this system can improve the safety of foundation pit excavation and avoid accidents caused by soil instability.

[0044] 2. The use of prestressed technology can apply prestress to the enclosure structure in advance to enhance its overall stability, thereby reducing the need for subsequent maintenance and repair.

[0045] 3. In addition to carrying the loading device, the lateral support can also be removably installed with a reaction frame, which can temporarily provide lateral loading force. In the process of the reaction frame providing lateral top force, the loading force of the loading device can be removed, and the weak interlayer on the surface of the embedded part pad can be cleaned before the loading device is installed in the predetermined position. The loading device then applies the lateral loading force again. The loading force applied by the loading device can directly act on the embedded part pad of the enclosure structure to ensure that the size and direction of the force can be accurately applied, thereby avoiding the weak interlayer originally existing in the loading area affecting the transmission of the lateral loading force.

[0046] 4. The detachable reaction frame can be reused, thereby reducing engineering costs and improving construction efficiency. In different construction stages, the reaction frame can be quickly installed and disassembled as needed, making the construction process more flexible.

[0047] The prestressed servo support system of the present invention is technically innovative, provides a new solution for foundation pit excavation, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 It is a top view of the prestressed servo support system and construction method of the advance support in the embodiment of the present invention.

[0050] Figure 2 yes Figure 1 AA section view.

[0051] Figure 3 It is a schematic diagram of the integral installation sequence of the lateral support mechanism in the first embodiment of the present invention.

[0052] Figure 4 It is a detailed view of the end of the prestressed servo support in Embodiment 1 and Embodiment 2 of the present invention.

[0053] Figure 5 It is a detailed diagram of BB in the first and second embodiments of the present invention.

[0054] Figure 6 It is a schematic diagram of the sequence of independent lifting and installation of each lateral support mechanism in the second embodiment of the present invention. DETAILED DESCRIPTION

[0055] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0056] In order to fully understand the present invention, detailed steps and detailed structures will be proposed in the following description to illustrate the technical solution of the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0057] The present invention provides a prestressed servo support system for supporting and loading before foundation pit excavation. Before the foundation pit excavation, a retaining structure 1 is arranged at the edge of the foundation pit, and a plurality of mutually parallel preformed grooves 19 are excavated in the area enclosed by the retaining structure 1. The prestressed servo support system arranged in the preformed grooves 19 includes a plurality of lateral support mechanisms which are sequentially distributed in parallel along the height direction of the foundation pit.

[0058] Each lateral support mechanism is provided with a support rod 5, one end of which is in contact with the inner wall of one side of the enclosure structure 1, and the other end of the support rod 5 is provided with a loading device 4, which includes a jack and a loading end 16 fixed on the telescopic rod of the jack, and the loading end 16 is driven by the jack to apply a force to the inner wall surface of the enclosure structure 1 to provide lateral support. In addition, a limiting mechanism 14 is also provided on the support rod 5.

[0059] A reaction frame 12 is detachably mounted on the other end of the support rod 5. The reaction frame 12 abuts between the limiting mechanism 14 and the inner wall of the other side of the enclosure 1. The rear end of the reaction frame 12 abuts on the limiting mechanism 14, and the front end of the reaction frame 12 is provided with a reaction loading mechanism 13 abutting thereon. The reaction frame 12 can play a role of temporary auxiliary support. The reaction frame 12 is installed on the support rod 5 and applies a force to the enclosure 1 through the reaction loading mechanism 13. Then, the loading force of the loading device 4 can be released, and the loading force is continued by the reaction frame 12. After the loading device 4 releases the loading force, it is very convenient to clean the inner wall of the enclosure in the loading area of ​​the loading device 4, and clean up the weak interlayer (such as silt) attached to the loading area. Then, the loading device 4 applies prestress again, so that the force applied by the loading device 4 can directly act on the enclosure 1, ensuring that the magnitude and direction of the force can be accurately applied, and avoiding the weak interlayer originally existing in the loading area from affecting the transmission of the loading force.

[0060] In an optional embodiment, a plurality of groups of lateral support mechanisms are arranged in the horizontal direction within the retaining structure 1, and each group of lateral support mechanisms is provided with a plurality of lateral support mechanisms which are distributed in parallel in sequence along the height direction of the foundation pit; a plurality of preformed grooves 19 are distributed at intervals in the original soil within the area enclosed by the retaining structure 1, and the preformed grooves 19 use mud wall protection 6, and at least one group of lateral support mechanisms is provided in the preformed grooves 19, and columns 7 are also provided in the original soil between adjacent preformed grooves 19.

[0061] In an optional embodiment, a plurality of water spray outlets are provided on the end face of the loading end head 16 facing the inner wall of the enclosure structure 1, a plurality of channels connected to the water spray outlets are provided inside the loading end head 16, and a water injection port connected to the channel is provided on the surface of the loading end head 16; each lateral support mechanism is provided with a cleaning mechanism, the cleaning mechanism includes a water pipe 17 connected to the water injection port, and the other end of the water pipe 17 is connected to a water pump or a high-pressure water gun. Before loading stress, the loading device 4 can inject water into the water pipe 17 through a water pump or a high-pressure water gun, and the high-pressure water injected into the water pipe 17 is sprayed out from the end face of the loading end head 16 to remove the soft mud residue between the loading end head 16 and the ground wall.

[0062] In an optional embodiment, the support rod 5 is a steel pipe, steel section or precast concrete pile, and the limiting mechanism 14 is a convex ring or block provided on the outer wall of the support rod 5, which is used to resist the reaction frame 12 to prevent the reaction frame 12 from sliding after applying stress.

[0063] A rubber bellows expansion tube 20 is sleeved on the outer surface of the loading device 4. Figure 5 As shown, one end of the rubber bellows is connected to the loading end 16, and the other end is fixed to the support rod 5, which plays a waterproof and anti-fouling role for the loading device 4, and the rubber bellows telescopic tube 20 can have a certain degree of elasticity. Regardless of whether the loading device 4 is extended or contracted, the rubber bellows telescopic tube 20 can always cover the outside of the loading device 4, effectively preventing the external environment from affecting the loading device 4. In addition, the rubber bellows telescopic tube 20 can also reduce the friction and collision between the loading device 4 and the outside world, thereby extending the service life of the device.

[0064] In an optional embodiment, the connection between the loading device 4 and the supporting rod 5 can be either a fixed connection (such as welding) or a detachable connection (such as screw connection). The loading device 4 preferably adopts a detachable connection, which is convenient for disassembling the loading device 4 as a whole during the actual construction process, so as to more conveniently clean the inner wall of the enclosure structure 1.

[0065] The loading device 4 and the reaction force loading mechanism 13 can use a servo jack, which can freely adjust the magnitude of the applied force. The use of the servo jack makes the loading device have higher accuracy and controllability when applying force. Through the electronic control system, real-time monitoring and adjustment of the loading force can be achieved to ensure that the magnitude of the applied force meets the specific requirements of the experiment or project.

[0066] In an optional embodiment, the whole is V-shaped, and is composed of two reaction blocks symmetrical about the center of the support rod 5. The support rod 5 is clamped between the two reaction blocks. After the arc bolt 15 passes through the two reaction blocks and is threaded, the two reaction blocks are fixedly connected together as a reaction frame 12, and the reaction frame 12 is fixedly installed on the support rod 5. The reaction frame 12 adopts a split design, which realizes that it can independently apply top force to provide temporary support without affecting the loading device 4.

[0067] In an optional embodiment, the inner wall of the enclosure structure 1 is provided with an embedded pad 3 for cooperating with the loading device 4 and the reaction loading mechanism 13. The embedded pad 3 is a steel plate larger than the force application area of ​​the loading device 4 and the reaction loading mechanism 13, ensuring that the loading force applied by the loading device 4 and the reaction loading mechanism 13 acts on the steel plate to avoid damage to the enclosure structure 1 of the concrete structure.

[0068] Embodiment 1

[0069] The following is a further description of the foundation pit excavation method using the above-mentioned prestressed servo support system:

[0070] S1. Construct the retaining structure 1 outside the area to be formed in the foundation pit. Among them, anchor steel bars 18 and embedded pads 3 are pre-embedded in the steel cage of the retaining structure 1. The pre-embedded positions of the anchor steel bars 18 and embedded pads 3 are consistent with the installation positions of the loading device 4 and the reaction loading mechanism 13 to ensure the transmission of force. Considering the construction error, the embedded pads 3 can appropriately use steel plates larger than the design size of the loading force area. After the construction of the retaining structure 1 is completed, several rows of columns 7 are inserted into the original soil of the area enclosed by the retaining structure 1.

[0071] S2. Anchors 8 are set outside the area where the advanced prestressed concrete support is erected, and a scaffolding machine 10 is set close to the foundation pit, and fixed to the upper part of the enclosure structure 1 by anchor bolts or other methods. After completing the above work, the installation and loading of the advanced support begins. First, equipment is used in the pit to preform slots 19 at predetermined positions. Each preformed slot 19 is located in the middle of the column 7. The preformed slot equipment can be a ground wall slot equipment. Mud wall 6 is used inside the preformed slot 19 to prevent soil collapse.

[0072] S3, the loading device 4 is installed at one end of the support rod 5 to form a transverse support mechanism, and a plurality of pre-installed support rods 5 are connected in series by using a steel strand 11, and then the lifting device lifts the connected support rods 5 into the pre-formed pre-grooves 19, as shown in FIG. Figure 3 Then, the steel strand 9 is fixed to the ground anchor 8, and the support rod 5 is provided with a vertical force by the racking machine 10 to prevent the support rods 5 connected in series from sinking in the mud of the preformed groove 19.

[0073] S4, use a high-pressure water gun to inject water into the water injection pipe 17, and remove the soft mud residue between the loading end 16 and the embedded part pad 3 through the water outlet at the front end of the loading end 16. Then, prestress is pre-applied to the enclosure structure 1 through the loading device 4. After the prestress loading is completed, the rack machine 10 and the hoisting steel strand 9 are removed. The steel strand 9 includes a first steel strand part for serially connecting the support rod 5 and a second steel strand part for connecting to the rack machine 10. The steel strand 9 can be completely removed or partially retained according to the situation. The specific situation is as follows: 1) All steel strands 9 are completely removed and the transverse support mechanism is retained in the preformed groove. 2) The second steel strand part is removed, and the first steel strand part connected between the support rods 5 is retained. The first steel strand can play a protective role. When the loading force strength of most transverse support mechanisms meets the requirements, when some transverse support mechanisms are displaced or fall due to insufficient loading force, the first steel strand can hang the transverse support mechanisms with insufficient loading force, play a protective role, and improve construction safety.

[0074] S5. Carry out earth excavation to the predetermined elevation.

[0075] S6. The V-shaped reaction frame 12 is fixed to the support rod 5 by bolts, and then the upper and lower reaction frames are fixedly connected together by arc-shaped bolts 15. The rear end of the reaction frame 12 abuts against the limit mechanism 14, and the reaction loading mechanism 13 at the front end of the reaction frame 12 is activated to apply a pre-loading force to the enclosure structure 1.

[0076] S7. Cancel the prestress applied by the loading device 4, and the jack retracts to drive the loading end 16 back to its original position. The loading device 4 can also be directly disassembled from the supporting rod 5 as a whole. After the loading device 4 releases the force, the inner wall of the enclosure structure in the force application area of ​​the loading device 4 is cleaned to clean the weak interlayer on the surface of the inner wall of the enclosure structure. The cleaning method can be to use the water outlet at the front end of the loading end 16 to spray water for cleaning, and other cleaning equipment and means can also be used to clean the weak interlayer on the surface of the embedded part pad 3. In this process, the reaction frame 12 applies a top force to continue to provide lateral support, so the loading device 4 can release the top force to facilitate the cleaning of the ground wall, so that the force applied by the loading device 4 can directly act on the enclosure structure 1, avoiding the weak interlayer originally existing in the loading area from affecting the transmission of the loading force.

[0077] S8, the loading device 4 is loaded again to the initial prestress, and then the prestress is continued to be loaded until the loading force requirement is met. The loading device 4 adopts a two-stage loading. The first step is to load to the same prestress as step S4, and then continue to load the prestress, which can effectively improve the stability and safety of the enclosure structure. During the loading process, the displacement and stress changes of the enclosure structure are monitored in real time to ensure the safety of the entire loading process. When the required prestress is reached, the data can be recorded by sensors and monitoring equipment to provide an accurate basis for subsequent structural analysis and evaluation. After the loading is completed, the enclosure structure is finally inspected to ensure that no abnormalities occur.

[0078] S9. After the loading device 4 has fully functioned, first remove the loading force of the reaction loading mechanism 13 at the front end of the reaction frame 12, then remove the reaction frame 12 from the supporting rod 5 as a whole, and use the loading device 4 to provide lateral loading. The removed reaction frame 12 is completely placed in the designated position to facilitate continued use next time.

[0079] S10, dividing the remaining soil layer to be excavated into N upper and lower layers for excavation layer by layer, and performing steps S6 to S9 once after each excavation to the next layer, until all excavations are completed to form a foundation pit located within the retaining structure 1.

[0080] It should be noted that after step S9 is completed, a concrete support 2 is constructed inside the retaining structure 1, and then subsequent layer-by-layer excavation steps are performed. The construction steps of the concrete support 2 are conventional technical means used by those skilled in the art and will not be described in detail here.

[0081] Embodiment 2

[0082] The difference between the second embodiment and the first embodiment is that the second embodiment is to independently hoist and fix each prestressed servo support. The specific difference is in step S3. The remaining steps are basically the same and will not be repeated here. Figure 6 , step S3 of this embodiment is described separately:

[0083] S3. Install the loading device 4 at one end of the support rod 5 and pre-install the transverse support mechanism. Then connect the steel strand 9 to each pre-installed support rod 5. Use the lifting equipment to independently lift the multiple pre-installed support rods 5 from bottom to top in sequence until they reach the predetermined elevation in the pre-formed pre-groove 19. Figure 6 As shown in a to e, five pre-installed support rods 5 are sequentially lowered into the pre-formed groove 19 from bottom to top. Then, the steel strands 9 are fixed to the ground anchors 8, and the support rods 5 are provided with vertical force by the gantry 10 to prevent the support rods 5 from sinking in the mud of the pre-formed groove 19.

[0084] In step S4 , after the loading device applies the initial prestress, the rack machine 10 and the hoisting steel strands 9 are completely removed, leaving only the transverse support mechanism in the preformed groove 19 .

[0085] The remaining steps can refer to the relevant steps of Example 1 and will not be repeated here. This Example 1 adopts the method of lowering the lateral support mechanism one by one, which makes the construction more flexible. In addition, since they are hoisted independently one by one, the position accuracy of each support rod can be better controlled during the construction process, ensuring the stability and reliability of the entire prestressed servo support system. In this way, the construction team can more accurately adjust the elevation of the support rods to adapt to the excavation requirements of foundation pits under different depths and geological conditions. In the end, this construction method not only improves the safety of the project, but also shortens the construction period and reduces costs.

[0086] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A prestressed servo support system for supporting and loading before foundation pit excavation, wherein a retaining structure is provided at the edge of the foundation pit, characterized in that: The prestressed servo support system comprises a plurality of lateral support mechanisms which are sequentially distributed in parallel along the height direction of the foundation pit; The lateral support mechanism is provided with a support rod, one end of which abuts against the inner wall of one side of the enclosure structure, and the other end of which is provided with a limiting mechanism and a loading device, wherein the loading device is provided with a loading end for abutting against the inner wall of the other side of the enclosure structure; A reaction frame is detachably mounted on the other end of the support rod, the reaction frame abuts between the limiting mechanism and the inner wall on the other side of the enclosure structure, the rear end of the reaction frame abuts on the limiting mechanism, and the front end of the reaction frame is provided with a reaction loading mechanism for abutting against the inner wall on the other side of the enclosure structure.

2. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 1, characterized in that: Several groups of transverse support mechanisms are arranged in the horizontal direction in the enclosure structure, and each group of transverse support mechanisms is provided with several transverse support mechanisms sequentially distributed in parallel along the height direction of the foundation pit; A plurality of preformed trenches are distributed at intervals in the original soil within the area enclosed by the enclosure structure. The preformed trenches are provided with mud walls, at least one set of transverse support mechanisms are provided in the preformed trenches, and columns are also provided in the original soil between adjacent preformed trenches.

3. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 1, characterized in that: The end surface of the loading end head facing the inner wall of the enclosure structure is provided with a plurality of water spraying ports, a channel connected to the water spraying ports is provided inside the loading end head, and a water injection port connected to the channel is provided on the surface of the loading end head; Each of the lateral supporting mechanisms is provided with a cleaning mechanism, and the cleaning mechanism comprises a water pipe connected to the water injection port, and the other end of the water pipe is connected to a water pump.

4. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 1, characterized in that: The support rod is a steel pipe, a steel section or a precast concrete pile, and the limiting mechanism is a convex ring or a stopper provided on the outer wall of the support rod; A rubber corrugated telescopic tube is sleeved on the outer surface of the loading device.

5. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 1, characterized in that: The loading device is detachably connected to the supporting rod; The loading device and / or the reaction force loading mechanism is a jack.

6. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 1, characterized in that: The reaction frame is provided with a plurality of reaction blocks which are symmetrical about the center of the support rod. The support rod is clamped in the middle of the plurality of reaction blocks. The plurality of reaction blocks are fixedly connected and installed on the support rod by bolts.

7. A prestressed servo support system for supporting and loading before foundation pit excavation as claimed in claim 2, characterized in that: The inner wall of the enclosure structure is provided with an embedded pad for cooperating with the loading device and the reaction force loading mechanism.

8. A construction method based on the prestressed servo support system according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: S1. Construct the enclosure structure outside the foundation pit to be formed. S2, excavating the original soil in the retaining structure to form a pre-formed trench, wherein the pre-formed trench is protected by mud; S3, lowering a plurality of the lateral support mechanisms installed with the loading device but not installed with the reaction frame into the prefabricated groove; S4, applying initial prestress to the enclosure structure using the loading device; S5. Carry out earth excavation to the predetermined elevation. S6, fixing the reaction frame on the support rod, and applying a loading force to the inner wall of the enclosure structure by using the reaction loading mechanism; S7, canceling the prestress applied by the loading device, and cleaning the inner wall of the enclosure structure in the force application area of ​​the loading device to clean the weak interlayer on the inner wall surface of the enclosure structure in the prestress loading area; S8, the loading device is loaded to an initial prestress, and then continues loading until the prestress requirement is reached; S9, canceling the loading force applied by the reaction force loading mechanism and removing the reaction force frame; S10, excavating the earth layer by layer, and performing steps S6 to S9 once each time the next layer is excavated to a specified height.

9. The construction method according to claim 8, characterized in that: In step S7, the loading device drives the loading end head to retract to cancel the prestress applied by the loading device.

10. The construction method according to claim 8, characterized in that: In step S7, after the loading device drives the loading end head to retract, the loading device is removed to cancel the prestress applied by the loading device; as well as In step S8, the disassembled loading device is installed back on the supporting rod, and then stress loading is performed.

11. The construction method according to claim 8, characterized in that: In step S4, before applying the initial prestress, the following steps are also included: The inner wall of the enclosure structure in the force application area of ​​the loading device is pre-cleaned by spraying water with the loading end head to flush away the sludge attached to the inner wall of the enclosure structure.

12. The construction method according to claim 8, characterized in that: In step S1, several rows of columns are inserted into the original soil in the enclosure structure. The preformed groove is arranged between adjacent columns.

13. The construction method according to claim 8, characterized in that: In step S3, the plurality of transverse support mechanisms without the reaction frame installed are first connected in series up and down in sequence through steel strands, and then the series-connected transverse support mechanisms are connected to a lifting device through the steel strands, and the series-connected transverse support mechanisms are lowered as a whole into the prefabricated groove through the lifting device; In step S4, after the loading device applies the initial prestress, the following steps are also included: Remove all the steel strands and keep the transverse support mechanism in the preformed groove, or The steel strands used for lifting are removed and the transverse supporting mechanisms and the steel strands connected between the transverse supporting mechanisms are retained in the preformed grooves.

14. The construction method according to claim 13, characterized in that: In step S3, the lateral support mechanism with the loading device installed but without the reaction frame installed is lowered into the prefabricated groove one by one from bottom to top by using a steel strand through a lifting device; In step S4, after the loading device applies the initial prestress, the following step is also included: removing the steel strands and retaining the transverse support mechanism in the preformed groove.

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