Deformation treatment method for rock stratum fracture zone of deep foundation pit

Abstract

According to the deformation treatment method for the rock stratum fracture zone of the deep foundation pit, by extending, densifying and additionally arranging the geological supplementary exploration holes outside the foundation pit, the spatial distribution depth, the internal specific structure, the rock fracture degree and the like of the rock stratum fracture zone are further ascertained, a basis is provided for improvement scheme design, and the deformation range of the foundation pit is divided according to the deformation degree of the foundation pit; different emergency and reinforcement treatments are adopted for deformation areas of different degrees, a steel support is additionally arranged in a foundation pit for emergency support treatment, reinforcement support replacement is conducted through a pre-stressed anchor cable and a low-pre-stressed anchor rod, and meanwhile parameters of the pre-stressed anchor cable and the low-pre-stressed anchor rod are optimized; the non-constructed full-sticky long mortar anchor rod area is changed into a low-prestress anchor rod for reinforcement; and a comprehensive treatment method of adding a steel pipe pile anchoring sliding body outside the foundation pit and grouting a sleeve valve pipe and the like is adopted.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit deformation management, and in particular relates to a method for managing deformation of a broken zone of a rock stratum in a deep foundation pit. Background Art

[0002] In the excavation of deep rock foundation pits, it is often easy to ignore the impact of fault fracture zones on deep foundation pits, and large deformation and collapse of foundation pits are common. The rock foundation pits appear to be very stable and safe on the surface, but in fact, once serious displacement and deformation problems occur, the foundation pits are prone to "packing dumplings", causing life safety and major economic losses to people. Therefore, it is necessary to strengthen the exploration of the strata around the rock foundation pits, and the hidden fault structures should be explored in detail and rectified to avoid large deformation of the foundation pits. The geology of rock foundation pits is generally covered by Quaternary clay layers and strongly weathered rock layers, and underlying moderately weathered and slightly weathered rocks. The rock strength is relatively high, the construction is difficult, and the construction progress is slow. Most of them require blasting operations or crushing with high-power mechanical equipment. Excavation, the design of the foundation pit retaining structure mostly adopts hanging piles, steel pipe piles, anchor cables (rods) and the first reinforced concrete support system. The hanging piles are bored cast-in-place piles, and a reinforced concrete ring beam is set on the top of the pile. The first prestressed anchor cable is set under the ring beam. Steel pipe piles are used for rock strata, and a reinforced concrete waist beam is set on the top of the steel pipe piles. Prestressed anchor cables are set at the waist beam. Anchor cables or low prestressed anchor rods are designed for other parts according to the layer height not more than 3m. Double-piece I-beam waist beams are used at the anchor cables, and No. 10 channel steel waist beams are used at the anchor rods. With the increase of the excavation depth of the foundation pit and the disturbance of the excavation on the surrounding area of ​​the foundation pit, the activity of the fault crushing zone is aggravated, resulting in abnormalities around the foundation pit, cracks in the ground, cracks in the positive corner concrete, and cracks on the surface of the primary support of the foundation pit. The foundation pit needs to be reinforced.

[0003] The related patent CN117552438A disclosed in the prior art specifically discloses a design method for active compensation support of deep foundation pits in soil-rock combined strata. This technical solution abandons the traditional passive support method and uses active force compensation methods such as anchor cables combined with high prestressed NPR anchor cables, W steel belts, etc. to complete the active support behavior of points, lines and surfaces of high prestressed compensation on the excavation surface of the foundation pit. According to the stress lost after the actual stratum excavation, the support parameters of the high prestressed NPR anchor cables are designed, thereby realizing compensation measures for the foundation pit;

[0004] The related patent CN115450222A disclosed in the prior art specifically discloses a construction method of a combined support structure for a foundation pit containing a broken sandstone layer. The technical solution involves excavating an anchor reinforcement groove on the side wall of the foundation pit, using an anchor drill to drill a hole at the anchor reinforcement groove, inserting anchor steel bars into the hole, and then injecting cement slurry into the hole. A reinforcement steel mesh is laid on the side wall of the foundation pit, concrete is poured into the anchor reinforcement groove, and steel purlins and anchor nuts are installed to anchor the anchor rods.

[0005] The relevant patent CN113605395A disclosed in the prior art specifically discloses a super-deep pit construction process under geological conditions of a large-area broken zone. The technical solution is to set a 20-30 cm thick grouting wall within the range to be grouting, open a number of through holes at the bottom of the lower side wall of the grouting wall, and install grouting pipes to grout and reinforce the broken zone. The main components of the grouting material are cement, sodium alginate, sodium silicate, phosphoric acid aqueous solution and medical stone powder.

[0006] The above existing technologies are unable to solve the problem of deformation control of broken zones in rock strata of deep foundation pits. Based on the above technical problems existing in the existing technologies, the present invention proposes a method for deformation control of broken zones in rock strata of deep foundation pits. Summary of the invention

[0007] The purpose of the present invention is to provide a method for treating deformation of a broken zone of a deep foundation pit rock layer in view of the deficiencies in the prior art.

[0008] The present invention adopts the following technical solution:

[0009] A method for treating deformation of a broken zone of a deep foundation pit rock layer, comprising:

[0010] Step 1: geological supplementary survey: at the location where the foundation pit slips, the drilling hole position is extended outside the foundation pit, and supplementary survey holes are added along the longitudinal direction of the foundation pit to find out the spatial distribution depth of the weak fracture zone, the specific internal structure and the degree of rock fragmentation;

[0011] Step 2: Divide the treatment area according to the location of the foundation pit deformation, and formulate treatment technical plans according to different treatment areas;

[0012] Step 3: According to the excavation and deformation of the foundation pit, emergency steel supports are set in the deformed area of ​​the excavated section;

[0013] Step 4: After the emergency steel support is erected in the excavated section and the support axial force is applied, a drilling operation platform is set up, and a pipe-roof drilling rig is used to drill holes for anchor cables or anchor rods in the deformation-affected area and deformation area of ​​the foundation pit, and reinforced prestressed anchor cables or anchor rods are installed for reinforcement before replacing the support. In the unexcavated section, the original designed pile-anchor support system is strengthened;

[0014] Step 5, construct the broken zone and its affected area, use down-the-hole drilling to drill a hole, the diameter of the hole is 15 to 20 cm larger than the diameter of the steel pipe, lower the anchor sliding body steel pipe, form a vertical steel pipe pile to anchor the sliding body, and use grouting to backfill the steel pipe pile and grouting to reinforce the broken zone;

[0015] Step 6: Drill holes with a geological drill in the area affected by the sliding surface outside the enclosure. The drilling depth is within the influence range of the weak fracture zone. Install sleeve valve pipes and use a plunger pump for grouting reinforcement.

[0016] Step 7, adjust the monitoring frequency and frequency, adopt automated monitoring means, install automated monitoring equipment and facilities, and conduct automated monitoring of the deformed foundation pit;

[0017] Step 8. After deformation control is completed, according to the stability of the monitoring data, first replace the emergency steel support at the bottom layer that affects the foundation pit excavation, then continue to excavate the foundation pit to the designed elevation and construct the main structure.

[0018] Furthermore, in step 1, the drilling hole extends outside the foundation pit by a distance of 5 to 10 m.

[0019] Furthermore, in step 1, two rows of supplementary exploration holes are added in the longitudinal direction.

[0020] Furthermore, in step 2, the foundation pit is divided into the affected area, the deformed area, the excavated section and the unexcavated section according to the different excavated depths, and a specific technical implementation plan is formulated for each area, including:

[0021] Erect emergency steel supports in the deformed areas of the excavated sections;

[0022] Additional reinforcement prestressed anchor cables are installed in the affected area and deformation area of ​​the excavated section;

[0023] Low prestressed anchors are added in the affected area and deformation area of ​​the excavated section;

[0024] The originally designed anchor cables or anchor rods shall be reinforced in the unexcavated section.

[0025] Furthermore, in step 2, the originally designed anchor cables are lengthened in the unconstructed sections.

[0026] Furthermore, in step 2, the originally designed full-length mortar anchor rods are changed to low-prestressed anchor rods in the unconstructed section.

[0027] Furthermore, in step 3, three emergency steel supports are added to the deformation area at the enlarged end of the excavated section to control the deformation of the foundation pit, including:

[0028] Support the first horizontal steel support on the crown beam;

[0029] Install the second horizontal steel support on the hanging pile locking waist beam;

[0030] Install the third horizontal steel support above the primary platform location.

[0031] Furthermore, in step 3, an emergency diagonal brace is installed on the wall of the enlarged end, and the diagonal brace is a steel support.

[0032] Further, in step 3, in the deformation area of ​​the excavated standard section, multiple emergency steel supports are set up according to the excavation depth to control the deformation of the foundation pit, including:

[0033] Set up the first horizontal steel support on the hanging pile locking waist beam;

[0034] Install the second horizontal steel support at the middle slab position;

[0035] The third horizontal steel support shall be set up 500mm above the low side wall of the base plate. If the excavation depth does not reach the base plate depth, the third horizontal steel support shall be set up 500mm above the excavation level.

[0036] Furthermore, in step 3, in the affected area where the excavation depth of the standard section is relatively shallow, emergency steel supports are erected for reinforcement, including:

[0037] Set up the first horizontal steel support on the hanging pile locking waist beam;

[0038] Install the second horizontal steel support at the middle slab location.

[0039] Furthermore, in step 3, the diameter of the emergency steel support is 800 mm, the wall thickness is 20 mm, and the horizontal spacing of the steel supports is not greater than 3 m.

[0040] Furthermore, the prestress applied to the emergency steel supports is 300KN.

[0041] Furthermore, in step 4, three reinforcing prestressed anchor cables are arranged in combination with a low prestressed anchor rod for reinforcement in the deformation-affected area of ​​the excavated enlarged end, including:

[0042] Two reinforcing prestressed anchor cables are arranged below the middle slab;

[0043] A reinforcing prestressed anchor cable is set under the steel pipe pile waist beam of the first-level platform;

[0044] A reinforcing low prestressed anchor rod is set above the corner of the first-level platform.

[0045] Further, in step 4, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are arranged in the deformation area of ​​the excavated enlarged end, including:

[0046] After the second horizontal steel support is installed on the locking foot waist beam, a reinforcing prestressed anchor cable is used to replace the second emergency steel support, and the reinforcing prestressed anchor cable is installed directly above the second horizontal steel support;

[0047] Two reinforcing prestressed anchor cables are installed within the range of the third horizontal steel support to replace the third emergency steel support. The two reinforcing prestressed anchor cables are installed above the third horizontal steel support.

[0048] A reinforcing prestressed anchor cable is installed directly below the first-level platform, that is, directly below the steel pipe pile waist beam;

[0049] A reinforcing low prestressed anchor rod is set above the corner of the first-level platform.

[0050] Furthermore, in step 4, prestressed anchor cables or low prestressed anchor rods are reinforced in the same layer of the deformation area and the affected area.

[0051] Furthermore, in step 4, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are arranged in the deformation area of ​​the excavated standard section, including:

[0052] A reinforcing prestressed anchor cable is installed directly above the second steel support to replace the second emergency steel support;

[0053] Install two reinforcing prestressed anchor cables above the third emergency steel support and one reinforcing prestressed anchor cable below the third emergency steel support to replace the third emergency steel support;

[0054] A reinforced low-stress anchor rod is installed at the low side wall of the base plate.

[0055] Further, in step 4, in the deformation area of ​​the excavated standard section, if the excavation depth does not reach the bottom plate position, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are set, including:

[0056] A reinforcing prestressed anchor cable is installed directly above the second steel support to replace the second emergency steel support;

[0057] Install two reinforcing prestressed anchor cables above and below the third emergency steel support respectively to replace the third emergency steel support;

[0058] Install a reinforcing prestressed anchor cable above the excavated rock surface;

[0059] Below the unexcavated rock layer, a reinforced low-stress anchor will replace the original full-length mortar anchor.

[0060] Furthermore, in step 4, in the standard section influence area, if the excavation depth does not reach the bottom plate position, four reinforcing prestressed anchor cables + one low prestressed anchor rod are set, including:

[0061] Two reinforcing prestressed anchor cables are installed above and below the second horizontal steel support respectively to replace the second emergency steel support;

[0062] Install a reinforcing prestressed anchor cable above the excavated rock surface;

[0063] Under the unexcavated rock layer, a reinforced prestressed anchor cable is used to replace the original fully bonded long mortar anchor rod for reinforcement design;

[0064] At the low side wall of the main structure below the unexcavated rock layer, a low prestressed anchor rod was used to replace the original fully bonded long mortar anchor rod to strengthen the design;

[0065] Furthermore, in step 4, two reinforcing prestressed anchor cables are arranged in the standard section influence area, including:

[0066] Install a reinforcing prestressed anchor cable above the excavated rock surface;

[0067] Below the unexcavated rock surface, a reinforced prestressed anchor cable will replace the original designed full-length mortar anchor for reinforcement.

[0068] Further, in step 4, the second enlarged end is an unexcavated section, and the prestressed anchor cable replaces the low prestressed anchor rod of the original design for reinforcement;

[0069] The low prestressed anchor rods were replaced with the original designed full-length mortar anchor rods for reinforcement.

[0070] Furthermore, in step 4, after each anchor cable is installed, the anchor cable hole is grouted using a plunger grouting pump in two steps. The first grouting is performed by injecting cement mortar through a primary grouting pipe located at the center hole of the anchor cable stringing ring. The second grouting is performed by injecting pure cement slurry through a secondary grouting pipe installed in a peripheral groove of the stringing ring. The slurry outlet and end of the secondary grouting pipe are sealed with tape to prevent the slurry from entering the secondary grouting pipe during the first grouting.

[0071] Furthermore, step 5 includes: the down-the-hole hammer drilling holes are arranged in a plum blossom shape, the holes are arranged to avoid the anchor cable positions, within the affected area, 3 rows of steel pipe piles are arranged along the longitudinal direction of the foundation pit in the expanded section, 5 rows of steel pipe piles are arranged along the longitudinal direction of the foundation pit in the standard section, and no less than 2 piles are extended to the non-affected area, and the drilling is performed by skipping holes with 2 piles at intervals, the drilling penetrates the slip surface into the intact slightly weathered rock layer for no less than 1.5m, and the bottom of the hole is cleaned with high-pressure air after the hole is formed.

[0072] Further, step 5 includes: the vertical grouting range is from 1.5 meters at the bottom of the soft and broken rock to 1.5 meters at the top of the soft and broken rock, the grouting slurry uses pure cement slurry, the slurry should be densely filled in the borehole and the steel pipe, and the grouting pressure is controlled at 0.3-0.4MPa;

[0073] Furthermore, step 6 includes:

[0074] The grouting adopts the method of grouting in separate holes, and the grouting pressure is controlled at 0.3-0.5Mpa. The grouting pressure of a single hole is gradually increased to the designed final pressure and grouting is continued for more than 10 minutes. The grouting volume is not less than 80% of the designed grouting volume. The grouting speed is 1 / 4 of the initial grouting speed. The grouting of this hole is terminated when the water inflow from the hole is less than 0.2L / min.

[0075] Furthermore, step 7 also includes setting up monitoring points, adding a number of automatic inclinometer monitoring points within the influence range of the broken rock and at the positive corners of the foundation pit; adding a number of inclinometer monitoring points using geological supplementary survey holes in areas where steel pipe piles have not been implemented; and adding monitoring points to monitor sections at stress concentration locations.

[0076] The beneficial effects of the present invention are:

[0077] 1. The method for treating deformation of rock fracture zones in deep foundation pits of the present invention extends to the outside of the foundation pit and adds additional geological exploration holes to further explore the spatial distribution depth of the rock fracture zones, the specific internal structure and the degree of rock fragmentation, etc., to provide a basis for the design of the treatment plan, and at the same time provide a reference for the scope that needs to be explored in the design process of similar deep foundation pits with rock fracture zones in the future. During the detailed exploration, an extended exploration method is adopted for the fracture zones to avoid the design of the retaining structure. The strength and stiffness cannot meet the requirements of the foundation pit excavation, resulting in the risk of deformation and collapse of the foundation pit;

[0078] 2. The method for treating deformation of broken rock zones in deep foundation pits of the present invention uses emergency steel supports as internal supports in the deformation area of ​​the foundation pit, which can quickly and effectively resist large deformation of the foundation pit and prevent the foundation pit from collapsing. When the emergency steel supports control the deformation of the foundation pit, construction safety is ensured. Reinforced anchor cables or anchor rods are then applied, and the emergency steel supports are removed without changing the design concept of the original pile-anchor system.

[0079] 3. The method for controlling deformation of the broken zone of rock strata in deep foundation pits described in the present invention utilizes emergency support within the retaining structure, reinforcement treatment of anchor cables (rods), and grouting of steel pipe columns and sleeve valve pipes to comprehensively control the broken zone of rock, giving full play to the dual effects of the anchoring force of rock anchor cables (rods) and the anti-slip of steel pipe piles, thereby improving the deformation resistance of the foundation pit. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is a plane schematic diagram of the rock crushing zone in the embodiment of the present invention;

[0081] Figure 2 This is a schematic cross-sectional view of the area affected by the first enlarged end in an embodiment of the present invention;

[0082] Figure 3 It is a cross-sectional schematic diagram of the deformation area of ​​the first enlarged end in an embodiment of the present invention;

[0083] Figure 4 It is a cross-sectional schematic diagram of the deformation area of ​​the standard section in an embodiment of the present invention;

[0084] Figure 5 This is a cross-sectional schematic diagram of the standard section influence area in an embodiment of the present invention;

[0085] Figure 6 Schematic diagram of the cross section of the area affected by the second enlarged end in an embodiment of the present invention.

[0086] In the figure, 1-slip surface, 2-slip body and area, 3-anti-slip steel pipe piles, 4-sleeve valve pipe, 5-reinforced prestressed anchor cable, 6-original design anchor cable, 7-emergency steel support, 8-guarding piles, 9-steel pipe piles, 11-full-adhesion long mortar anchor rod, 12-middle plate, 13-low side wall, 14-low prestressed anchor rod. DETAILED DESCRIPTION

[0087] In order to more clearly understand the above-mentioned purposes, features and advantages of the present invention, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0088] Example

[0089] like Figure 1-6 As shown, the method for treating deformation of the broken zone of the deep foundation pit rock stratum includes:

[0090] Step 1: geological reconnaissance: at the location where the foundation pit slips, the drilling hole position is extended outside the foundation pit, and reconnaissance holes are added along the longitudinal direction of the foundation pit to find out the spatial distribution depth of the weak fracture zone, the specific internal structure and the degree of rock fragmentation, so as to provide a basis for the design of the remediation plan;

[0091] Step 2: According to the location of the deformation of the foundation pit, the foundation pit is divided into treatment areas according to the excavation depth, deformation and deformation impact degree. Treatment technical plans are formulated according to different treatment areas. The original construction drawing design concept is not changed. The support system is mainly designed with pile anchors, and internal support steel supports are constructed as temporary emergency supports;

[0092] Step 3: according to the excavation and deformation of the foundation pit, an emergency steel support 7 is set in the deformed area of ​​the excavated section, the design parameters of the emergency steel support 7 are clarified, a large-tonnage truck crane is used for lifting, the emergency steel support 7 is erected, and the support axial force is applied;

[0093] Step 4: After the emergency steel support 7 is erected and the supporting axial force is applied in the excavated section, a drilling operation platform is set up, and a pipe shed drilling rig is used to drill holes for anchor cables or anchor rods in the deformation affected area and the deformation area of ​​the foundation pit, and reinforced prestressed anchor cables or anchor rods are installed for reinforcement and then the support is replaced. In the unexcavated section, the originally designed pile anchor support system is strengthened;

[0094] Step 5: Drill holes in the broken zone and its affected area by using a down-the-hole drill. The diameter of the drill hole is 15 to 20 cm larger than the diameter of the steel pipe. Use a car crane to lower the steel pipe for anchoring the sliding body to form a vertical anti-sliding steel pipe pile 3 to anchor the sliding body and the area 2. At the same time, grouting is used to backfill the anti-sliding steel pipe pile 3 and grouting reinforcement is performed on the broken zone;

[0095] Step 6: Drill holes with a geological drill in the area affected by the sliding surface 1 outside the enclosure. The drilling depth is within the affected range of the weak fracture zone (10 m below the surface), install the sleeve valve pipe 4, and perform grouting reinforcement with a plunger pump;

[0096] Step 7, adjust the monitoring frequency and frequency, adopt automated monitoring means, install automated monitoring equipment and facilities, and conduct automated monitoring of the deformed foundation pit;

[0097] Step 8, after deformation control is completed, according to the stability of the monitoring data, first replace the emergency steel support 7 at the bottom layer that affects the foundation pit excavation, then continue to excavate the foundation pit to the designed elevation and construct the main structure.

[0098] As a specific implementation, in step 1, the drilling hole extends outward by a distance of 5 to 10 m.

[0099] As a specific implementation, in step 1, two rows of supplementary survey holes are added in the longitudinal direction.

[0100] As a specific implementation method, in step 2, the expanded ends at both ends of the station and the middle standard section are divided into affected areas and deformation areas, as well as excavated sections and unexcavated sections, and specific technical implementation plans are formulated for each area, including;

[0101] Emergency steel supports 7 are set up in the deformed areas of the excavated section;

[0102] 5 reinforcing prestressed anchor cables are added to the affected area and deformation area of ​​the excavated section;

[0103] Low prestressed anchors 14 are added to the affected area and deformation area of ​​the excavated section;

[0104] The unexcavated section will be reinforced with the originally designed anchor cables 6 or anchor rods.

[0105] As a specific implementation, in step 2, the originally designed anchor cable 6 is lengthened in the unconstructed section.

[0106] As a specific implementation, in step 2, the originally designed full-length mortar anchor rod 11 in the unconstructed section is changed to a low prestressed anchor rod 14.

[0107] As a specific implementation method, in step 2, three emergency steel supports 7 are added to the deformation area at the enlarged end of the excavated section to control the deformation of the foundation pit, including:

[0108] Support the first horizontal steel support on the crown beam;

[0109] Install the second horizontal steel support on the hanging pile locking waist beam;

[0110] Install the third horizontal steel support above the primary platform location.

[0111] As a specific implementation method, in step 2, an emergency diagonal brace is installed on the expanded end wall, and the diagonal brace is a steel support.

[0112] As a specific implementation method, in step 3, in the deformation area of ​​the excavated standard section, multiple emergency steel supports 7 are set up according to the excavation depth to control the deformation of the foundation pit, including:

[0113] Set up the first horizontal steel support on the hanging pile locking waist beam;

[0114] Install the second horizontal steel support at the middle slab position;

[0115] The third horizontal steel support is set up 500mm above the bottom plate low side wall 13. If the excavation depth does not reach the bottom plate depth, the third horizontal steel support is set up 500mm above the excavation level.

[0116] As a specific implementation method, in step 3, in the affected area where the excavation depth of the standard section is relatively shallow, multiple emergency steel supports 7 are set up for reinforcement, including:

[0117] Set up the first horizontal steel support on the hanging pile locking waist beam;

[0118] Install the second horizontal steel support at the middle slab location.

[0119] For example, the steel support is assembled on the ground and divided into two sections. One of the large-tonnage cranes lifts the two sections of the steel support into the foundation pit respectively and connects them in the foundation pit. After the connection is completed, two large-tonnage cranes stand on both sides of the foundation pit respectively and lift and install the steel support at the same time.

[0120] Exemplarily, the emergency steel support 7 has a diameter of 800 mm, a wall thickness of 20 mm, and a horizontal spacing of the steel supports of no more than 3 m.

[0121] Exemplarily, the prestress applied is 300 KN.

[0122] As a specific implementation method, in step 4, three reinforcing prestressed anchor cables 5 and one low prestressed anchor rod 14 are arranged in the deformation-affected area of ​​the excavated enlarged end for reinforcement, including:

[0123] Two reinforcing prestressed anchor cables 5 are arranged below the middle slab;

[0124] A reinforcing prestressed anchor cable 5 is arranged below the waist beam of the steel pipe pile of the first-level platform;

[0125] A reinforcing low prestressed anchor rod 14 is arranged above the corner of the first-level platform.

[0126] As a specific implementation, in step 4, four reinforcing prestressed anchor cables 5 and one low prestressed anchor rod 14 are arranged in the excavated enlarged end deformation area, including:

[0127] After the second horizontal steel support is installed on the locking foot waist beam, the second emergency steel support 7 is replaced by a reinforcing prestressed anchor cable 5, and the reinforcing prestressed anchor cable 5 is installed directly above the second horizontal steel support;

[0128] Install two reinforcing prestressed anchor cables 5 within the range of the third horizontal steel support to replace the third emergency steel support 7, and install the two reinforcing prestressed anchor cables 5 above the third horizontal steel support;

[0129] A reinforcing prestressed anchor cable 5 is installed directly below the first-level platform, that is, directly below the steel pipe pile waist beam;

[0130] A reinforcing low prestressed anchor rod 14 is arranged above the corner of the first-level platform.

[0131] As a specific implementation, in step 4, the prestressed anchor cables 5 or low prestressed anchor rods 14 are reinforced in the same layer of the deformation area and the affected area.

[0132] As a specific implementation, in step 4, four reinforcing prestressed anchor cables 5 and one low prestressed anchor rod 14 are arranged in the deformation area of ​​the excavated standard section, including:

[0133] A reinforcing prestressed anchor cable 5 is installed directly above the second steel support to replace the second emergency steel support 7;

[0134] Install two reinforcing prestressed anchor cables 5 above the third emergency steel support 7 and one reinforcing prestressed anchor cable 5 below the third emergency steel support 7 to replace the third emergency steel support 7;

[0135] A reinforcing low stress anchor rod 14 is installed on the bottom plate short side wall 13 .

[0136] As a specific implementation, in step 4, in the excavated standard section deformation area, where the excavation depth does not reach the bottom plate position, four reinforcing prestressed anchor cables 5 and one low prestressed anchor rod 14 are set, including:

[0137] A reinforcing prestressed anchor cable 5 is installed directly above the second steel support to replace the second emergency steel support 7;

[0138] Install two reinforcing prestressed anchor cables 5 above and below the third emergency steel support 7, respectively, to replace the third emergency steel support 7;

[0139] Install a reinforcing prestressed anchor cable 5 above the excavated rock surface;

[0140] Under the unexcavated rock layer, a reinforced low-stress anchor rod 14 replaces the originally designed full-length mortar anchor rod 11.

[0141] As a specific implementation, in step 4, four reinforcing prestressed anchor cables 5 and one low prestressed anchor rod 14 are arranged in the affected area where the excavation depth of the standard section is relatively shallow, including:

[0142] Two reinforcing prestressed anchor cables 5 are respectively installed above and below the second horizontal steel support to replace the second emergency steel support; one reinforcing prestressed anchor cable 5 is installed above the excavated rock layer; in the unexcavated rock layer below the rock layer, one reinforcing prestressed anchor cable replaces the original designed full-length mortar anchor rod 11 for reinforcement design; at the position of the short side wall 13 of the main structure of the unexcavated rock layer, one low prestressed anchor rod 14 replaces the original designed full-length mortar anchor rod 11 for reinforcement design.

[0143] As a specific implementation, in step 4, two reinforcing prestressed anchor cables 5 are arranged in the standard section influence area, including:

[0144] Install a reinforcing prestressed anchor cable 5 above the excavated rock surface;

[0145] In the unexcavated rock layer below the rock layer surface, a reinforced prestressed anchor cable is used to replace the original designed full-length mortar anchor rod 11 for reinforcement design.

[0146] As a specific implementation method, in step 4, in the unexcavated section at the second enlarged end, the prestressed anchor cable replaces the originally designed low prestressed anchor rod 14 for strengthening the design;

[0147] The low prestressed anchor rod 14 replaces the originally designed full-length mortar anchor rod 11.

[0148] It should be noted that the construction of anchor cables is affected by the excavation depth of the foundation pit and requires high-altitude operations, which are difficult to construct. After the construction of the first reinforced prestressed anchor cable 5 is completed, an operating platform is set up, holes are drilled with a pipe-roof drilling rig, and anchor cables are installed; for drilling holes in the middle layer of anchor cables, an operating platform can be set up on the excavated rock surface, holes can be drilled with a pipe-roof drilling rig, and anchor cables can be installed; for anchor cables above the excavated rock surface, holes can be drilled directly with a crawler down-the-hole drill on the excavated rock surface; for anchor cables or anchor rods in the unexcavated sections, holes can be drilled and anchor cables or anchor rods can be installed at any time with a crawler down-the-hole drill as the rock excavation progresses.

[0149] For example, the diameter of the anchor hole is 150mm, the material is steel strand, the strength of the steel strand is 1860Mpa, the length of the anchor is 16-24m, the length of the anchoring section is 6-9m, and the incident angle is 15°-20°; after the grouting slurry reaches the strength, prestress is applied with a through-type jack, and the pre-stressed axial force is 200KN.

[0150] Exemplarily, the low prestressed anchor rod 14 uses a third-grade threaded steel bar with a diameter of 28, an anchor rod length of 6 to 10 m, an incident angle of 15°, and a preloaded axial force of 80 KN.

[0151] In addition, after each anchor cable is installed, the anchor cable hole is grouted with a plunger grouting pump in two times. The first grouting is injected with cement mortar through the primary grouting pipe, which is located at the center hole of the anchor cable stringing ring. The second grouting is injected with pure cement slurry through the secondary grouting pipe. The secondary grouting pipe is installed in the peripheral groove of the stringing ring. The grouting hole and the end of the secondary grouting pipe are sealed with adhesive tape to prevent the slurry from entering the secondary grouting pipe during the first grouting. The secondary grouting is carried out after the strength of the first grouting reaches more than 5Mpa. The secondary grouting adopts high-pressure grouting method with a grouting pressure of 2.5Mpa~4Mpa. The grouting slurry is mixed with an early strength agent to improve the early strength, shorten the anchor cable tensioning time, and speed up the overall construction progress.

[0152] As a specific implementation method, step 5 includes: the down-the-hole hammer drilling holes are arranged in a plum blossom shape, the holes are arranged to avoid the anchor position, within the affected area, 3 rows of steel pipe piles 9 are set along the longitudinal direction of the foundation pit in the expanded section, and 5 rows of steel pipe piles 9 are set along the longitudinal direction of the foundation pit in the standard section, and no less than 2 piles are extended to the non-affected area. The drilling is performed by skipping holes with an interval of 2 piles. The drilling penetrates the sliding surface into the complete slightly weathered rock layer for no less than 1.5m, and the bottom of the hole is cleaned with high-pressure air after the hole is formed.

[0153] As a specific implementation method, step 5 includes: the steel pipe pile 9 is made of Q345 seamless steel pipe, the steel pipe is connected to the inner liner casing, the welding adopts groove welding and multi-layer welding, and the weld needs to be polished to ensure that the steel pipe connection is straight and without bending.

[0154] Exemplarily, the steel pipe pile 9 is a steel flower pipe, and the holes drilled in the pipe wall are arranged in a plum blossom shape.

[0155] As a specific implementation method, step 5 includes: the vertical grouting range is 1.5 meters from the bottom of the soft and broken rock to 1.5 meters from the top of the soft and broken rock, the grouting slurry uses pure cement slurry, the slurry should be densely filled in the borehole and the steel pipe, and the grouting pressure is controlled at 0.3-0.4MPa;

[0156] As a specific implementation, step 6 includes:

[0157] The grouting adopts the method of grouting in separate holes, and the grouting pressure is controlled at 0.3-0.5Mpa. The grouting pressure of a single hole is gradually increased to the designed final pressure and grouting is continued for more than 10 minutes. The grouting volume is not less than 80% of the designed grouting volume. The grouting speed is 1 / 4 of the initial grouting speed. The grouting of this hole is terminated when the water inflow from the hole is less than 0.2L / min.

[0158] As a specific implementation method, step 7 also includes setting up monitoring points, adding a number of automatic inclinometer monitoring points within the influence range of the broken rock and the positive corners of the foundation pit; adding a number of inclinometer monitoring points using geological supplementary exploration holes in areas where steel pipe piles 9 are not implemented; and adding monitoring points to monitor sections at stress concentration locations.

[0159] As a specific implementation method, in step 2, the two ends of the station are respectively the first expanded end and the second expanded end, the middle part of the station is the standard section, and the station adopts the middle trough excavation method, and excavates from the first expanded end with a small mileage to the second expanded end with a large mileage, that is, first excavate the first expanded end, then excavate the middle standard section, and finally excavate the second expanded end; when the small mileage foundation pit is excavated to the bottom plate, the foundation pit is deformed, and its foundation pit deformation area occurs from the 4th to the 7th axis at the positive corner of the first expanded end to the 7th to the 11th axis of the standard section. The adjacent positions at both ends of the foundation pit deformation position, that is, the 2nd to the 4th axis of the first expanded end and the 11th to the 14th axis of the standard section are determined as the affected area, and the 14th to the 21st axis of the second expanded end is a large span excavation, and the unexcavated section is reinforced according to the affected area.

[0160] As a specific implementation method, in step 3, emergency steel supports 7 are first installed as internal supports in the deformed area to control deformation; three horizontal emergency steel supports 7 are added to axles 4 to 7 of the small-mileage expansion end, and two emergency diagonal braces are added to the auxiliary end wall of the expansion end; three horizontal emergency steel supports 7 are added to axles 7 to 11 of the standard section, and one horizontal steel support is added to axles 11 to 14 of the standard section for reinforcement.

[0161] Exemplarily, three emergency steel supports 7 are set at the first end of the expansion end, supported on the crown beam, five emergency steel supports 7 are set at the second end, installed at the lock-foot waist beam position, 8.6 meters away from the first steel support, and five emergency steel supports 7 are set at the third end, installed 3.7 meters above the position of the first-level platform and 6.5 meters away from the second steel support. If the needs of the main structure concrete construction are considered, two reinforcing anchor cables 5 are used to replace the support; three reinforcing anchor rods are constructed within the range of the third emergency steel support 7, and the foundation pit is excavated. After the structure is constructed to the middle plate 12, the uppermost anchor cable is constructed, and after the support is removed, the main structure is constructed upwards; two emergency inclined braces are added to the auxiliary end wall of the small-mileage expansion section. The braces are steel supports, for example, steel supports with a diameter of φ800mm, a wall thickness of 20mm, and a pre-loaded axial force of 300KN are used.

[0162] Exemplarily, three emergency steel supports 7 are added to the standard sections 7 to 11 axes. For example, the diameter of the steel supports is φ800mm, the wall thickness is 20mm, and the pre-loaded axial force is 300KN. The first emergency steel support 7 is arranged at the locking foot waist beam position of axes 7 to 11. Exemplarily, 15 steel supports are installed, 9.4 meters from the ground; Exemplarily, 11 steel supports are installed at axes 7 to 11; the third emergency steel support 7 is arranged at the counter-pressure soil platform position of axes 7 to 10, Exemplarily, it is 8.55 meters away from the second emergency steel support, and 6 steel supports are installed.

[0163] Exemplarily, a steel support reinforcement treatment is added to the standard sections 11 to 14 shafts. For example, the steel support has a diameter of φ800mm, a wall thickness of 20mm, a pre-loaded axial force of 300KN, and the reinforced steel support is installed at the locking foot waist beam position.

[0164] As a specific implementation method, Figure 2-6 As shown, in step 4, in order to reinforce the sliding body foundation pit support system, for example, three prestressed anchor cables and a low prestressed anchor rod 14 are added to the 2-5 axis for reinforcement. The first reinforcing prestressed anchor cable 5 is set at the negative third layer middle plate 12 position, the length of the anchor cable is 14m, the length of the anchor section is 6m, and the incident angle is 15°; the second reinforcing prestressed anchor cable 5 is set at the third emergency steel support 7, the length of the anchor cable is 14m, the length of the anchor section is 6m, and the incident angle is 15°; the Three reinforcing prestressed anchor cables 5 are arranged under the concrete crown beam of the secondary foundation pit auxiliary platform. The length of the anchor cable is 17m, the length of the anchoring section is 6m, and the incident angle is 15°; one reinforcing low prestressed anchor rod 14 is arranged at the foot of the auxiliary structure platform. The length of the reinforced low prestressed anchor rod 14 is 8m, and the incident angle is 15°; the third emergency steel support 7 adopts the first and second reinforcing prestressed anchor cables 5 for replacement support. After the construction of the reinforcing prestressed anchor cables 5 is completed, the emergency steel support 7 is removed.

[0165] On this basis, four prestressed anchor cables and one low prestressed anchor rod 14 are added to the 5-7 axis for reinforcement. The setting positions of the four reinforced prestressed anchor cables 5 are consistent with the position height and design parameters of the three reinforced prestressed anchor cables 5 of the 2-5 axis, which will not be repeated here. Another reinforced prestressed anchor cable 5 is set below the concrete crown beam of the hanging pile. For example, the length of the anchor cable is 17m, the length of the anchoring section is 6m, and the incident angle is 20°. When the main structure of this anchor cable is constructed to the position of the second emergency steel support 7, an operating platform is set up to first construct this reinforced prestressed anchor cable 5, and the second emergency steel support 7 is replaced and removed. The design position height and parameters of a reinforced low prestressed anchor rod 14 are consistent with those of a reinforced low prestressed anchor rod 14 of the 2-5 axis, and a channel steel waist beam is added.

[0166] On this basis, 4 prestressed anchor cables and a low prestressed anchor rod 14 are added to the standard section 7-11 axis for reinforcement. The first reinforcing prestressed anchor cable 5 is arranged above the negative second floor middle plate 12, that is, above the second emergency steel support 7. For example, the length of the anchor cable is 24m, the length of the anchor section is 8m, and the incident angle is 15°; the second reinforcing prestressed anchor cable 5 is arranged above the negative third floor middle plate 12. For example, the length of the anchor cable is 20m, the length of the anchor section is 6m, and the incident angle is 15°; the third and fourth reinforcing prestressed anchor cables are arranged below the negative third floor middle plate 12, that is, above the third emergency steel support 7 and at the track top air duct. For example, the length of the anchor cable is 18m, the length of the anchor section is 6m, and the incident angle is 15°. The length of the fixed section is 6m, and the incident angle is 20°; a reinforcing low prestressed anchor rod 14 is set at the position of the low side wall 13 of the bottom plate, for example, the length of the anchor rod is 10m, and the incident angle is 15°; during construction, first construct the third and fourth anchor cables of the third steel support, set up the construction operation platform, construct the second anchor cable, remove the third emergency steel support 7, excavate the counter-pressure soil below, construct the low prestressed anchor rod 14, excavate to the bottom, construct the structural bottom plate, construct the negative third layer middle plate 12 upwards, set up scaffolding, construct the first anchor cable, remove the second emergency steel support 7, construct the negative second structure middle plate 12, remove the first emergency steel support 7, construct the negative first layer side wall and structural top plate;

[0167] Four prestressed anchor cables and one low prestressed anchor rod 14 are added to the 11-14 axis for reinforcement or strengthening, wherein two prestressed anchor cables and one low prestressed anchor rod 14 are used to replace the three full-length mortar anchor rods 11 originally designed for reinforcement. The first reinforcing prestressed anchor cable 5 is arranged above the negative second layer middle plate 12, that is, above the second emergency steel support 7, for example, the length of the anchor cable is 24m, the length of the anchor section is 8m, and the angle of incidence is 15°; the second reinforcing prestressed anchor cable 5 is arranged above the negative third layer middle plate 12, for example, the length of the anchor cable is 20m, the length of the anchor section is 6m, and the angle of incidence is 15°; the third and fourth reinforcing prestressed anchor cables are arranged below the negative third layer middle plate 12, that is, at the track top air duct, for example, the lengths of the anchor cables are 17m and 16m respectively, the lengths of the anchor section are 6m, and the angle of incidence is 20°; a reinforcing low prestressed anchor rod 14 is arranged on the short side wall 13 of the bottom plate, for example, the length of the anchor rod is 10m, and the angle of incidence is 15°. During construction, the second reinforcing prestressed anchor cable 5 is constructed, the foundation pit stone is excavated, and the replacement is carried out in sequence. The third and fourth reinforced prestressed anchor cables and reinforced low prestressed anchor rods 14 are constructed in sequence upward after the foundation pit is excavated to the bottom. The structural bottom plate, the negative third floor side wall, and the negative third floor middle plate 12 are constructed upward, and the negative second floor side wall is continued to be constructed. The second emergency steel support 7 is removed and the negative second floor middle plate 12 is constructed. After the concrete reaches 75% of the design strength, a pipe shed drilling rig is used to drill holes in the negative second floor middle plate 12, and the first reinforced prestressed anchor cable 5 is constructed. The negative first floor side wall is constructed, the first emergency steel support 7 is removed, and the structural top plate is constructed. If the excavated foundation pit is deep, the reinforced prestressed anchor cable 5 or anchor rod construction is difficult, and there is no construction site for large-scale operating equipment. During construction, a scaffolding operating platform needs to be set up, and a pipe shed drilling rig is used on the platform to drill holes and install anchor cables (rods); a down-the-hole drill is used to drill holes in the unexcavated section, and then the anchor cables (rods) are installed;

[0168] The 12-14 axis is outside the influence range of the sliding body, and two prestressed anchor cables are added, wherein: the first reinforcing prestressed anchor cable 5 is arranged in the middle of the negative second floor side wall, and is used to reinforce the enclosure structure, for example, the anchor cable length is 12m, the anchoring section length is 6m, and the incident angle is 15°; the second reinforcing prestressed anchor cable 5 is arranged at the negative third floor rail top air duct, and is used to replace the original design full-viscosity mortar anchor rod 11. During construction, a down-the-hole drill can be used to directly drill holes on the excavated rock layer, for example, the anchor cable length is 12m, the anchoring section length is 6m, and the incident angle is 15°;

[0169] Two reinforced prestressed anchor cables and one reinforced low prestressed anchor rod 14 are added to the large-mileage unexcavated expansion section 14-15 axis to replace the originally designed full-length mortar anchor rod 11. The first reinforced prestressed anchor cable is arranged in the middle of the negative second floor side wall, for example, the anchor cable length is 18m, the anchor section length is 9m, and the incident angle is 15°; the second reinforced prestressed anchor cable is arranged at the negative third floor track top air duct, for example, the anchor cable length is 18m, the anchor section length is 9m, and the incident angle is 15°, which is used to replace the full-length mortar anchor rod 11 at this position, and a reinforced prestressed anchor rod is arranged below the second reinforced anchor cable.

[0170] In addition, a reinforcement anchor cable is added to the end wall at the positive angle of the large mileage unexcavated expansion section. For example, the anchor cable length is 18m, the anchor end length is 6m, the incident angle is 15°, and the position is set below the two locking anchor cables of the hanging pile, and a channel steel waist beam is added;

[0171] At the 15-21 axis of the unexcavated expansion section of the large mileage and the large mileage end wall, the four full-length mortar anchors 11 below the original designed locking anchor cable are replaced with one reinforcement anchor cable and three reinforcement prestressed anchors in sequence. For example, the reinforcement anchor cable is 14m long, the anchor end length is 6m, the incident angle is 15°, and the lengths of the prestressed reinforcement anchors are 10m, 8m, and 7m respectively, and the incident angles are all 15°;

[0172] As a specific implementation method, in step 4, a down-the-hole hammer is used to drill holes within the enclosure of the foundation pit. For example, the diameter of the drill hole is 500 mm, the diameter of the steel pipe pile 9 is φ377 mm, the wall thickness is 12 mm, the steel pipe material is Q345, the hole spacing is 4mx3m, and the drill holes are arranged in a plum blossom shape. The holes are arranged to avoid the positions of the two anchor cables of the first and second layers. Within the scope of the affected area, for example, three rows of steel pipe piles 9 are arranged along the longitudinal direction of the foundation pit in the expanded section, and three rows of steel pipe piles 9 are arranged along the longitudinal direction of the foundation pit in the standard section. 5 rows of steel pipe piles 9, and extend no less than 2 piles to the non-affected area. The drilling is performed by skipping holes with 2 piles at intervals. The drilling depth should penetrate the sliding surface into the complete slightly weathered rock layer and be no less than 1.5m. During the drilling process, check the borehole diameter and verticality every 2-3m. If the pile position is found to be incorrect or tilted, backfill cement mortar to 300mm-500mm above the offset hole position, adjust or re-drill. During the entire drilling process, no bentonite or other suspended Floating mud is used as the drilling wall protection. After the hole is formed, high-pressure wind is used to clean the bottom of the hole. First, the inner casing method is used on the ground to connect and weld the steel pipe pile 9 firmly. The welding adopts groove welding and multi-layer welding method. When connecting, the smoothness of the steel pipe is controlled to prevent warping, and the weld is polished to ensure that the verticality of the steel pipe meets the requirements. Two eye holes are drilled at the axial position of the top of the steel pipe pile 9, and two lifting ears are installed. Use a 150T crane to hoist it into the hole as a whole. The steel pipe pile 9 is a steel flower pipe, and the pipe wall Drill 5mm holes in a plum blossom-shaped arrangement with a vertical spacing of 50cm and 3 to 4 holes in the annulus. The vertical grouting range is from 1.5 meters at the bottom of the soft and broken rock to 1.5 meters at the top of the soft and broken rock. The grouting slurry uses pure cement slurry, which densely fills the drilled holes and steel pipes. The grouting pressure is controlled at 0.3 to 0.4MPa. Tests are carried out before construction to determine the grouting pressure. The pressure is gradually increased during the test, and observations are made through monitoring and measurement data to ensure that the grouting test will not further increase the deformation of the foundation pit.

[0173] As a specific implementation method, in step 5, the spacing of the boreholes is 2mX2m, and they are arranged in a plum blossom shape. The grouting slurry uses pure cement slurry with a water-cement ratio of 1:1. If groundwater is developed, cement and water glass double liquid slurry can be used. During grouting, the inter-hole grouting method is adopted, and the grouting pressure is strictly controlled. The grouting pressure is controlled at 0.3-0.5Mpa. The grouting is ended by multi-control indicators. The grouting pressure of a single hole is gradually increased to the designed final pressure and the grouting is continued for more than 10 minutes. The grouting volume is not less than 80% of the designed grouting volume. The grouting speed is 1 / 4 of the initial grouting speed. The grouting of this hole can be ended only when the water inflow of the hole is less than 0.2L / min. After the grouting is completed, the grouting quality of the grouting weak points is checked by core sampling. The number of inspection holes is not less than 2% and not less than 3 holes in each section. The permeability coefficient of the soil after grouting is less than 10 -6cm / s, unconfined compressive strength is not less than 0.8Mpa, the location and depth of the test holes are arranged within 1-2m outside the structural outline, and those that fail the test should be treated with grouting. For blind areas in reinforcement, re-drilling, adjusting the angle, and supplementing grouting;

[0174] On this basis, in step 5, 7 automatic inclinometer monitoring points are added within the influence range of broken rock and at the positive corners of the foundation pit, and inclinometer monitoring points are added where conditions permit in areas where 9 steel pipe piles have not been implemented for a long mileage. At the same time, supplementary geological boreholes are used as inclinometer monitoring points. For example, 5 monitoring sections are added at the end, 1 monitoring section is added at the end of the shield shaft, and 1 monitoring section is added at the positive corner. The monitoring section for the horizontal and vertical displacement of the pile top of the foundation pit is adjusted to 10 meters, the number of monitoring sections is increased, and the monitoring points for the horizontal displacement of the pile top and the vertical displacement of the pile top corresponding to the monitoring section are increased accordingly; the monitoring section for surface settlement around the foundation pit is adjusted to 10 meters, the number of monitoring sections is increased, and the surrounding surface settlement corresponding to the monitoring section is The number of monitoring points shall be increased accordingly, and measuring points shall be added at the newly erected emergency steel supports 7 in the foundation pit. The monitoring number of each support layer should not be less than 10% of the number of supports on each layer, and should not be less than 3. Steel support axial force monitoring points shall be arranged in each area and each layer of the newly erected emergency steel supports 7, and one measuring point shall be arranged for every 2 emergency steel supports 7. Automated monitoring methods shall be adopted for the deep horizontal displacement monitoring of the retaining piles 8 and the support axial force (anchor stress); the deep horizontal displacement monitoring of the retaining piles 8 covers the entire monitoring period, and the monitoring point and the object to be measured are always a solid whole during the monitoring process, and the displacement change of the measuring point occurs with the corresponding deformation of the object to be measured; if an unexpected change in the sensor position occurs, it shall be recalibrated.

[0175] The present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which are within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for treating deformation of a broken zone in a deep foundation pit, characterized in that: include: Step 1: geological supplementary survey: at the location where the foundation pit slips, the drilling hole position is extended outside the foundation pit, and supplementary survey holes are added along the longitudinal direction of the foundation pit to find out the spatial distribution depth of the weak fracture zone, the specific internal structure and the degree of rock fragmentation; Step 2: Divide the treatment area according to the location of the foundation pit deformation, and formulate treatment technical plans according to different treatment areas; Step 3: According to the excavation and deformation of the foundation pit, emergency steel supports are set in the deformed area of ​​the excavated section; Step 4: After the emergency steel support is erected in the excavated section and the support axial force is applied, a drilling operation platform is set up, and a pipe-roof drilling rig is used to drill holes for anchor cables or anchor rods in the deformation-affected area and deformation area of ​​the foundation pit, and reinforced prestressed anchor cables or anchor rods are installed for reinforcement before replacing the support. In the unexcavated section, the originally designed pile-anchor support system is strengthened; Step 5, construct the broken zone and its affected area, use down-the-hole drilling to drill a hole, the diameter of the hole is 15 to 20 cm larger than the diameter of the steel pipe, lower the anchor sliding body steel pipe, form a vertical steel pipe pile to anchor the sliding body, and use grouting to backfill the steel pipe pile and grouting to reinforce the broken zone; Step 6: Drill holes with a geological drill in the area affected by the sliding surface outside the enclosure. The drilling depth is within the influence range of the weak fracture zone. Install sleeve valve pipes and use a plunger pump for grouting reinforcement. Step 7, adjust the monitoring frequency and frequency, adopt automated monitoring means, install automated monitoring equipment and facilities, and conduct automated monitoring of the deformed foundation pit; Step 8. After deformation control is completed, according to the stability of the monitoring data, first replace the emergency steel support at the bottom layer that affects the foundation pit excavation, then continue to excavate the foundation pit to the designed elevation and construct the main structure.

2. The method for treating deformation of a broken zone in a deep foundation pit according to claim 1, characterized in that: In step 2, the foundation pit is divided into the affected area, deformation area, excavation section and unexcavated section according to the different excavation depths, and a technical implementation plan is formulated for each area, including: Erect emergency steel supports in the deformed areas of the excavated sections; Additional reinforcement prestressed anchor cables are installed in the affected area and deformation area of ​​the excavated section; Low prestressed anchors are added in the affected area and deformation area of ​​the excavated section; The originally designed anchor cables or anchor rods shall be reinforced in the unexcavated section.

3. The method for treating deformation of a broken zone of a deep foundation pit according to claim 1, characterized in that: In step 3, three emergency steel supports are added to the deformation area at the expanded end of the excavated section to control the deformation of the foundation pit, including: Support the first horizontal steel support on the crown beam; Install the second horizontal steel support on the hanging pile locking waist beam; Install the third horizontal steel support above the primary platform location.

4. The method for treating deformation of a broken zone in a deep foundation pit according to claim 1, characterized in that: In step 3, in the deformation area of ​​the excavated standard section, multiple emergency steel supports are set up according to the excavation depth to control the deformation of the foundation pit, including; Set up the first horizontal steel support on the hanging pile locking waist beam; Install the second horizontal steel support at the middle slab position; The third horizontal steel support shall be set up 500mm above the low side wall of the base plate. If the excavation depth does not reach the base plate depth, the third horizontal steel support shall be set up 500mm above the excavation level.

5. The method for treating deformation of a broken zone of a deep foundation pit according to claim 1, characterized in that: In step 4, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are set in the deformation area of ​​the excavated enlarged end, including: After the second horizontal steel support is installed on the locking foot waist beam, a reinforcing prestressed anchor cable is used to replace the second emergency steel support, and the reinforcing prestressed anchor cable is installed directly above the second horizontal steel support; Two reinforcing prestressed anchor cables are installed within the range of the third horizontal steel support to replace the third emergency steel support. The two reinforcing prestressed anchor cables are installed above the third horizontal steel support. A reinforcing prestressed anchor cable is installed directly below the first-level platform, that is, directly below the steel pipe pile waist beam; A reinforcing low prestressed anchor rod is set above the corner of the first-level platform.

6. The method for treating deformation of a broken zone of a deep foundation pit according to claim 1, characterized in that: In step 4, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are set in the deformation area of ​​the excavated standard section, including: A reinforcing prestressed anchor cable is installed directly above the second steel support to replace the second emergency steel support; Install two reinforcing prestressed anchor cables above the third emergency steel support and one reinforcing prestressed anchor cable below the third emergency steel support to replace the third emergency steel support; A reinforced low-stress anchor rod is installed at the low side wall of the base plate.

7. The method for treating deformation of a broken zone in a deep foundation pit according to claim 1, characterized in that: In step 4, in the deformation area of ​​the excavated standard section, where the excavation depth does not reach the bottom plate position, four reinforcing prestressed anchor cables combined with a low prestressed anchor rod are set, including: A reinforcing prestressed anchor cable is installed directly above the second steel support to replace the second emergency steel support; Install two reinforcing prestressed anchor cables above and below the third emergency steel support respectively to replace the third emergency steel support; Install a reinforcing prestressed anchor cable above the excavated rock surface; Below the unexcavated rock layer, a reinforced low-stress anchor will replace the original anchor.

8. The method for treating deformation of a broken zone in a deep foundation pit according to claim 1, characterized in that: In step 4, two reinforcing prestressed anchor cables are set in the standard section influence area, including: Install a reinforcing prestressed anchor cable above the excavated rock surface; Below the unexcavated rock surface, a reinforced prestressed anchor cable will replace the original designed full-length mortar anchor for reinforcement.

9. The method for treating deformation of a broken zone in a deep foundation pit according to claim 1, characterized in that: In step 4, after each anchor cable is installed, the anchor cable hole is grouted using a plunger grouting pump in two steps. The first grouting is injected with cement mortar through a primary grouting pipe located at the center hole of the anchor cable stringing ring. The second grouting is injected with pure cement slurry through a secondary grouting pipe installed in the peripheral groove of the stringing ring. The slurry outlet and end of the secondary grouting pipe are sealed with tape to prevent the slurry from entering the secondary grouting pipe during the first grouting.

10. The method for treating deformation of a broken zone of a deep foundation pit according to claim 1, characterized in that: Step 7 also includes setting up monitoring points, adding a number of automatic inclinometer monitoring points within the influence range of the broken rock and at the positive corners of the foundation pit; adding a number of inclinometer monitoring points using geological supplementary survey holes in areas where steel pipe piles have not been implemented; and adding monitoring points to monitor sections at stress concentration locations.

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