Foundation pit supporting construction method under complex geological conditions

Abstract

According to the foundation pit supporting construction method under the complex geological condition, pre-buried holes can be formed after concrete pouring, drilling and positioning are facilitated, segmented pressure maintaining can be achieved during grouting, grout permeates into a soil body through the grout permeating holes, a tree root structure is formed in the soil body, contact between the sleeve and the soil body is enhanced, the soil body is reinforced, and meanwhile the foundation pit supporting effect is improved. The method comprises the following steps: excavating an upper-layer earth, pre-burying a pre-buried pipe, reinforcing the pre-buried pipe, spraying concrete, dismantling the pre-buried pipe, manufacturing a neck bush pipe, installing a sleeve, secondarily installing the neck bush pipe, installing the anchor rod, pulling the neck bush pipe, and repeating the step S10 for multiple times to pull the neck bush pipe and maintain the pressure. And S12, installing a waist beam until the neck bush pipe is completely pulled out of the soil body, excavating the earthwork again, and repeating the steps S2-S12 to support and excavate the multi-layer earthwork until the foundation pit support is completed.

Description

Technical Field

[0001] The invention relates to foundation pit support, in particular to a foundation pit support construction method under complex geological conditions. Background Art

[0002] The foundation pit is an earth pit excavated at the foundation design position according to the base elevation and foundation plane dimensions. During the excavation of the foundation pit, in order to ensure the safety of the underground structure construction and the surrounding environment of the foundation pit, it is necessary to adopt support, reinforcement and protection measures for the side walls of the foundation pit and the surrounding environment.

[0003] Foundation pit support is divided into shallow pit support and deep pit support. Deep pit support includes soil nail wall support, steel sheet pile support, cement soil wall support, internal support of pile row, soil layer anchor support of pile row, retaining cast-in-place pile row or underground continuous wall support and composite soil nail wall foundation pit support. The traditional construction method of composite soil nail wall foundation pit support is generally to drill holes for anchor cables on the slope first, then carry out grouting construction, and then carry out surface steel mesh and surface concrete spraying construction.

[0004] Traditional composite soil nail wall foundation pit support has high requirements for traditional geological conditions and environments. Foundation pit support is carried out under complex geological adjustments of large-diameter pebbles and underground water layers. Due to poor soil conditions, high soil water content and relatively soft soil, when drilling anchor holes, the drilling process will cause a certain degree of disturbance to the soil, which may cause local slip or collapse of the foundation pit slope. In order to avoid such situations, the support method of pre-spraying the surface layer + post-anchor cable is generally adopted. The surface steel mesh and surface concrete are sprayed first to improve the slope strength and the initial support strength. After the pre-spraying surface layer is formed, the foundation pit slope has been initially protected, reducing the disturbance of the soil by subsequent anchor cable drilling construction and reducing the risk of soil slippage. Then anchor cable drilling and grouting construction are carried out.

[0005] When drilling anchor holes, due to poor soil conditions, high water content, and soft soil, the anchor holes are relatively unstable and prone to collapse. At the same time, the soil bearing capacity is low and the anchoring effect is poor. When drilling anchor holes, it may disturb adjacent holes. Soil disturbance may cause adjacent holes to collapse, resulting in insufficient grouting in the holes, affecting the anchoring effect of the anchor in the soil, making it difficult to drill anchor holes under complex geological conditions after the surface concrete spraying construction. Summary of the invention

[0006] In order to solve the problem in the background technology that anchor holes are prone to collapse and the anchoring effect is poor under poor soil conditions, the present invention proposes a foundation pit support construction method under complex geological conditions.

[0007] The technical solution of the present invention is: S1 Upper earthwork excavation: excavate one layer of earthwork; S2 pre-buried pipe: locate the anchor hole and drill the positioning hole, insert the front end of the pre-buried pipe into the positioning hole, and movably set a protective sleeve on the pre-buried pipe, and the rear part of the pre-buried pipe is located outside the soil; S3 Pre-buried pipe reinforcement: The pre-buried fixing parts are inserted into the soil, and the pre-buried fixing parts are provided with connectors connected to the protective sleeves on the pre-buried pipes; S4 spraying concrete: spray concrete in layers and lay steel mesh to form a concrete layer; S5: Remove the embedded pipes: remove the embedded pipes, demould the embedded pipes from the protective sleeves, and form embedded openings on the concrete layer; S6 liner casing production: standard sections are produced in sections, and the standard sections are spliced ​​to form the liner casing; S7 casing installation: There are multiple grouting holes on the sleeve, and a liner sleeve is inserted into the sleeve. The casing and the drilling rig simultaneously open anchor holes in the embedded opening toward the soil. After the drilling is completed, the liner sleeve is removed; S8 liner casing secondary installation: Install a sealing plug on one end of the liner casing inserted into the anchor hole, and install the liner casing into the sleeve for the second time; S9 Anchor installation: The anchor is installed into the sleeve, and the front end of the anchor passes through the sealing plug; S10 Pulling out the liner casing: Pull out the liner casing in sections according to the design, and remove the liner casing from the soil. After pulling out, perform pressure grouting. During pressure grouting, the slurry penetrates into the soil through the grouting holes. Repeat S10 for multiple times to pull out the liner casing and maintain pressure until the liner casing is completely pulled out of the soil; S11 waist beam installation: The waist beam is installed on the concrete slope, the anchor rod is connected to the waist beam, and then prestress is applied to the anchor rod; S12 Earthwork re-excavation: earthwork re-excavation is carried out after the upper support is completed; Repeat S2-S12 to support and excavate multiple layers of earth until the foundation pit support is completed.

[0008] Preferably, the inner liner sleeve in S6 includes multiple standard sections, the rear end of the standard section is the insertion end, the front section of the standard section is the socket end, the insertion end is provided with a thread, and the socket end is provided with a thread structure adapted to the insertion end. Multiple standard sections are inserted into the socket end through the insertion end and can be detachably connected to form the inner liner sleeve.

[0009] Preferably, the embedded fixing member in S3 comprises an embedded rod, an insertion rod and a connecting rod, the front end of the embedded rod is provided with an insertion rod for inserting into the soil, and the rear end of the embedded rod is provided with a connecting screw; The embedded rod is provided with a transparent connection hole for connecting with the connecting piece; The length of the embedded rod is greater than the thickness of the sprayed concrete layer.

[0010] Preferably, the sealing plug in S9 comprises a mounting ring and a sealing ring, the width of the mounting ring is greater than the width of the sealing ring, the mounting ring is provided with a connecting hole for connecting with the liner sleeve, and the connecting hole is connected with the liner sleeve by a bolt; The sealing ring is provided with an escape opening for the anchor rod to pass through.

[0011] Preferably, in the S7, a plurality of transparent infiltration holes are provided on the sleeve, the plurality of infiltration holes are evenly spaced around the axis of the sleeve, each infiltration hole group includes a plurality of infiltration holes, and the infiltration holes are evenly spaced along the extension direction of the sleeve.

[0012] Preferably, the waist beam in S11 is detachably connected to the concrete layer via a connecting screw.

[0013] Preferably, the waist beam comprises two support beams, a plurality of connecting plates and connecting plates, the support beams are provided with connecting holes for connecting screws to pass through, the support beams are arranged horizontally, and the two support beams are located in corresponding positions up and down, and an installation gap is left between the two support beams; A plurality of connecting plates are arranged on the support beam at intervals on the left and right sides, the upper portion of the connecting plates is welded to the outer surface of the support beam located on the upper side, and the lower portion of the connecting plates is welded to the outer surface of the support beam located on the lower side; A connecting plate is arranged between two adjacent waist beams, and both left and right ends of the connecting plate extend into the installation gap on the waist beam on the same side, and the connecting plate is detachably connected to the two supporting beams on the same side.

[0014] Preferably, the support beam is provided with a vertically transparent plug hole, and a mounting rod that can be extended vertically is provided between the two support beams, and the upper and lower ends of the mounting rod are respectively plugged into the adjacent plug holes; A connection socket is provided on the connection plate, and the installation rod passes through the connection socket.

[0015] Preferably, the mounting rod includes a sleeve and a screw, the sleeve is inserted between two adjacent upper and lower sockets, the upper end of the sleeve is fixedly connected to a limiting plate, the width of the limiting plate is greater than the diameter of the connecting socket, a threaded connecting groove with a lower opening is provided in the sleeve, a screw is threadedly connected in the threaded connecting groove, and the lower end of the screw is fixedly connected to a limiting block, the width of the limiting block is greater than the diameter of the connecting socket.

[0016] Preferably, the front side of the support beam is detachably connected to a mounting plate by bolts, a pad is fixedly connected to the mounting plate, the pad has an inclination adapted to the anchor rod, a front and rear transparent avoidance hole is opened on the pad, the avoidance hole corresponds to the installation gap position front and rear, an anchor is fixedly connected to the pad, and the front end of the anchor cable passes through the installation gap and the avoidance hole and is fixedly connected to the anchor.

[0017] The advantages of the present invention are as follows: when pouring concrete, a pre-buried opening can be reserved through the pre-buried pipe. After the pre-cast concrete layer, the influence of the concrete layer on the hole position accuracy can be reduced. At the same time, when the casing is sent into the anchor rod borehole for support, the slurry is injected into the casing, and the slurry is sent into the anchor rod borehole through the casing. During grouting, the slurry can be infiltrated into the soil layer through the grouting hole to form a tree root structure, thereby strengthening the connection between the casing and the soil. In addition, the casing is pressure-maintained in sections, so that grouting with different pressures can be performed in different structural layers, thereby avoiding excessive infiltration of the slurry into the soil, which would damage the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 work.

[0019] Figure 1 This is a schematic diagram of the waist beam installation construction structure; Figure 2 This is a schematic diagram of the construction structure for pulling out the liner casing; Figure 3 This is a schematic diagram of the pre-buried pipe reinforcement construction structure; Figure 4 This is a schematic diagram of the waist beam structure; Figure 5 It is a schematic diagram of the partial cross-sectional structure of the waist beam; Figure 6 It is a schematic diagram of the structure of the embedded fixing parts; Figure 7 is a schematic diagram of the casing structure; Figure 8 It is a schematic diagram of the local structure of the liner casing; Fig. 9 It is a schematic diagram of the partial cross-sectional structure of the liner casing.

[0020] In the figure, 1 is a supporting beam, 2 is a connecting plate, 3 is a connecting plate, 4 is a mounting rod, 401 is a sleeve, 402 is a screw, 5 is a connecting socket, 6 is a mounting plate, 7 is a pad, 8 is an anchor, 9 is an embedded pipe, 10 is a protective cover, 11 is an embedded fixing, 111 is an embedded rod, 112 is a plug, 113 is a connecting screw, 12 is a sleeve, 13 is an inner lining sleeve, and 14 is a sealing plug. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1: This embodiment aims to propose a foundation pit support construction method under complex geological conditions.

[0023] according to Figures 1 to 9 As shown in the figure, the foundation pit support construction method under complex geological conditions includes the following steps: S1 Excavation of upper earthwork: The elevation coordinates measured by the planning unit are used as the reference point. The theodolite, level and tape measure are used for measurement and layout. The earthwork is excavated according to the design slope requirements. The earthwork is excavated in layers according to the design. The lower earthwork can only be excavated after the concrete surface layer of the upper earthwork is sprayed with concrete and reaches the design strength of concrete.

[0024] Pre-buried pipe 9 is pre-buried: the foundation pit wall after excavation is trimmed, and the anchor hole position is determined by a level and a steel ruler according to the elevation and horizontal spacing required by the design. A positioning hole is preliminarily drilled at the hole position, and the front end of the embedded pipe 9 is inserted into the positioning hole. A protective cover 10 is movably sleeved on the embedded pipe 9. In this embodiment, a PU film can be selected for the protective cover 10, and the PU film covers the outside of the protective cover 10. The front end of the embedded pipe 9 is located in the positioning hole, and the rear part of the embedded pipe 9 is exposed outside the soil.

[0025] Pre-buried pipe 9 reinforcement: Pre-buried fixing piece 11 is inserted into the soil, and a connecting piece connected to the protective cover 10 on the pre-buried pipe 9 is provided on the pre-buried fixing piece 11; The embedded fixing member 11 comprises an embedded rod 111 , an insertion rod 112 and a connecting rod. The front end of the embedded rod 111 is provided with the insertion rod 112 for inserting into the soil, and the rear end of the embedded rod 111 is provided with a connecting screw 113402 .

[0026] The embedded rod 111 is provided with a transparent connection hole for connecting with a connecting piece. The connecting piece can be an iron wire in this embodiment. One end of the iron wire passes through the connection hole and is fixedly connected to the embedded rod 111 , and the other end of the iron wire is tied to the protective cover 10 .

[0027] Spraying concrete: first spray concrete on the bottom layer. The crushed stone used for spraying concrete is 5-10mm, the sand is medium-coarse sand, and the water content of the sand is controlled at 5% to 7%. The gravel should be hard crushed stone, and its maximum gravel diameter should not be greater than 10mm. Before spraying concrete, the required materials should be evenly mixed in proportion. The required air compressor, spraying concrete pipe, and water for spraying concrete should be debugged and standby before spraying concrete. The spraying sequence should be from bottom to top, and the nozzle and the soil nail wall should be kept vertical. After the bottom layer is sprayed concrete, the steel mesh is laid. After the steel mesh is laid, the surface layer is sprayed concrete. The added thickness of the concrete of the surface layer sprayed concrete and the bottom layer sprayed concrete is less than the length of the embedded rod 111 and the length of the protective cover 10. When spraying concrete, the concrete only covers the embedded rod 111 and the protective cover 10, and does not contact the embedded pipe 9; During concrete spraying, the embedded rod 111 and the embedded pipe 9 are partially covered with the protective cover 10 by the concrete, so that after the concrete strength reaches the standard, the embedded fixing member 11 is embedded in the concrete surface layer.

[0028] Removing the embedded pipe 9: manually removing the embedded pipe 9, demoulding the embedded pipe 9 from the protective cover 10, and leaving the protective cover 10 in the hole, so that the embedded opening is formed on the concrete layer.

[0029] Production of the liner sleeve 13: standard sections are produced in sections, the rear end of the standard section is the insertion end, the front section of the standard section is the socket end, the insertion end is provided with a thread, the socket end is provided with a thread structure adapted to the insertion end, multiple standard sections are inserted into the socket end through the insertion end and can be detachably connected to form the liner sleeve 13, and the standard sections are spliced ​​to form the liner sleeve 13.

[0030] Installation of casing 12: Multiple grouting holes are provided on the casing 401. Multiple transparent groups of grouting holes are provided on the casing 401. The multiple groups of grouting holes are evenly spaced around the axis of the casing 401. Each group of grouting holes includes multiple grouting holes. The grouting holes are evenly spaced along the extension direction of the casing 401. An inner liner sleeve 401 is inserted in the casing 401. The casing 12 and the drilling rig simultaneously open anchor holes in the embedded opening toward the soil direction. The holes are drilled to the rock layer. The drilling rig is connected to the casing 12 and drilling is performed simultaneously. Leaving the casing 12 in the hole after drilling is a prior art and will not be repeated in this embodiment. After the drilling is completed, the inner liner sleeve 401 is pulled out from the casing 12.

[0031] Secondary installation of the liner sleeve 13: a sealing plug 14 is installed at one end of the liner sleeve 13 inserted into the anchor hole, and the liner sleeve 13 is secondarily installed in the sleeve 401; The sealing plug 14 includes a mounting ring and a sealing ring. The width of the mounting ring is greater than that of the sealing ring. The mounting ring is provided with a connecting hole for connecting to the inner liner sleeve 13. The connecting hole is connected to the inner liner sleeve 13 by bolts. The sealing ring is provided with an avoidance opening, and the anchor rod can pass through the avoidance opening. The shape of the avoidance opening is adapted to the shape of the anchor rod. After the anchor rod is inserted into the avoidance opening, the sealing ring can perform sealing.

[0032] Anchor rod installation: insert the anchor rod into the sleeve 401 and center the anchor rod. When the anchor rod is inserted, the front end of the anchor rod passes through the avoidance opening on the sealing ring, and the front end of the anchor rod passes through the sealing plug 14 and extends to the bottom of the anchor rod drilling hole.

[0033] Pulling out the liner casing 13: Pulling out the liner casing 401 in sections according to the design. According to the different structures of the rock layer and the soil layer of the soil, pull out the liner casing 13 of different lengths in sections. The pulling out length corresponds to the thickness of the structural layer, so that the position of the sealing ring is located at the intersection of the two structural layers, so that the pressure of the pressure-maintaining grouting between different structural layers is different. After pulling out, the part of the liner casing 13 leaking out of the soil is removed; After pulling out, pressure-maintaining grouting is performed. During grouting, the grouting equipment delivers slurry into the anchor hole through the grouting pipe. In this embodiment, cement slurry can be selected. The slurry fills the gap in the casing 12. The sealing ring seals the slurry in the casing 12 so that the slurry does not flow out of the sealing part of the sealing ring. After the front cavity of the casing 12 is filled, the slurry penetrates into the soil through the grouting hole.

[0034] Repeat S10 for multiple times to pull out and maintain the pressure of the liner casing 13, so that each soil layer is pressure-maintained in sections according to its soil layer strength, until the liner casing 13 is completely pulled out of the soil. After the front slurry solidifies, it is pulled out again. The cavity generated by the first pulling out is the first cavity. After the pressure-maintaining grouting of the first cavity is completed and solidified, it is pulled out again. A new cavity is generated in the casing 12 as the second cavity, and then pressure-maintaining grouting is performed again. After the slurry fills the second cavity, the slurry penetrates into the soil through the grouting holes under the action of pressure. Different structural layers have different materials in the structural layers. For example, the rock layer has a larger structural strength and the gaps between the gravel are smaller, so a larger pressure is required. , the slurry can penetrate into the soil. Because there is more silt in the soil layer and the structural strength is low, and there are large gaps between the mud and sand, the slurry can penetrate into the soil with a smaller pressure. If the same pressure as the rock layer is used, too much slurry will penetrate into the soil. At the same time, pressure-maintaining grouting with different pressures is carried out according to the soil layer in which it is located. Different pressures are injected according to the different levels of the grouting position. The pressure at the grouting pipe mouth is detected by a pressure gauge to detect the grouting pressure, so as to carry out segmented pressure-maintaining grouting in different soil layers to avoid the use of the same pressure grouting, which will cause excessive slurry to penetrate into the loose soil layer, thereby causing the soil layer to be destroyed.

[0035] Waist beam installation: The waist beam is installed on the concrete slope, the anchor rod is connected to the waist beam, and then prestress is applied to the anchor rod; The waist beam in S11 is detachably connected to the concrete layer through a connecting screw 113402. The waist beam includes two supporting beams 1, a plurality of connecting plates 2 and a connecting plate 3. The supporting beam 1 is provided with a connecting socket 5 for the connecting screw 113402 to pass through. The supporting beam 1 is horizontally arranged, and the two supporting beams 1 are positioned correspondingly up and down, with an installation gap left between the two supporting beams 1. A plurality of connecting plates 2 are arranged on the supporting beam 1 at intervals on the left and right. The upper part of the connecting plate 2 is welded to the outer surface of the supporting beam 1 located on the upper side, and the lower part of the connecting plate 2 is welded to the outer surface of the supporting beam 1 located on the lower side.

[0036] A connecting plate 3 is provided between two adjacent waist beams, and a socket that is transparent from top to bottom is provided on the support beam 1. A mounting rod 4 that can be telescoped up and down is provided between the two support beams 1. The upper and lower ends of the mounting rod 4 are respectively plugged into the adjacent sockets. A connecting socket 5 is provided on the connecting plate 3, and the mounting rod 4 passes through the connecting socket 5. The mounting rod 4 includes a sleeve 401 and a screw 402. The sleeve 401 is inserted between two adjacent sockets. The upper end of the sleeve 401 is fixedly connected to a limiting plate, and the width of the limiting plate is greater than the diameter of the connecting socket 5. A threaded connecting groove with a lower opening is provided in the sleeve 401, and a screw 402 is threadedly connected in the threaded connecting groove. The lower end of the screw 402 is fixedly connected to a limiting block, and the width of the limiting block is greater than the diameter of the connecting socket 5.

[0037] The left and right ends of the connecting plate 3 both extend into the installation gap on the waist beam on the same side, and the connecting plate 3 is detachably connected to the two supporting beams 1 on the same side.

[0038] The front side of the support beam 1 is detachably connected to a mounting plate 6 by bolts, to which a pad 7 is fixedly connected. The pad 7 has an inclination adapted to the anchor rod, and a front-to-back transparent avoidance hole is opened on the pad 7. The avoidance hole corresponds to the front-to-back position of the mounting gap. An anchor 8 is fixedly connected to the pad 7. In this embodiment, the anchor 8 is prior art and will not be described in detail. The front end of the anchor cable passes through the mounting gap and the avoidance hole and is fixedly connected to the anchor 8.

[0039] Second excavation of earthwork: earthwork excavation is carried out again after the upper support is completed.

[0040] Repeat S2-S12 to support and excavate multiple layers of earth until the foundation pit support is completed.

[0041] Thus, the embedded pipe 9 can be pre-buried to leave an embedded opening after concrete is sprayed. At the same time, since the embedded pipe 9 is provided with a protective sleeve 10, after the concrete is solidified, the protective sleeve 10 is fixedly connected to the concrete layer, and the embedded pipe 9 can be quickly pulled out. In the prior art, the embedded pipe 9 needs to be pulled out by knocking the embedded pipe 9 or the concrete layer near the embedded pipe 9, which is difficult to pull out and is easy to damage the hole wall.

[0042] After pulling out the embedded pipe 9, drilling is performed at the embedded pipe 9 to drill the anchor hole to the rock layer. Then the casing 12 and the liner casing 13 are connected to the drilling rig and drilled into the anchor hole synchronously. The liner casing 13 can prevent mud and sand from entering the casing 12 during drilling.

[0043] The lining casing 13 is pulled out according to the thickness of the structural layer, and pressure-maintaining grouting with different pressures is carried out in different structural layers. At the same time, the sealing plug 14 on the lining casing 13 is used to control the slurry in the cavity corresponding to the structural layer during grouting, thereby achieving segmented pressure maintenance for different structural layers to avoid damaging the soil. At the same time, the pressure is maintained in sections quickly to save materials.

[0044] During the pressure-maintaining grouting, the slurry penetrates into the soil through the grouting holes. After the slurry penetrates into the soil, it contacts the soil, forming a root structure in the soil, increasing the contact between the sleeve 401 and the soil, and reinforcing the soil at the same time.

[0045] Pre-embedding avoids the need to drill holes in the concrete layer, making positioning more accurate and eliminating the need to drill holes in the concrete surface layer, reducing the difficulty of drilling operations. The casing 12 is drilled into the borehole together with the drill bit to support the borehole and avoid collapse of the borehole during drilling. At the same time, during grouting, the slurry penetrates into the soil through the casing 12 to enhance the contact between the casing 12 and the soil. At the same time, the slurry penetrates into the soil to form a root structure, thereby enhancing the bearing capacity of the soil and improving the anchoring effect.

[0046] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is limited by the appended claims rather than the above description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. The foundation pit support construction method under complex geological conditions is characterized by: The following steps are involved: S1 Upper earthwork excavation: excavate one layer of earthwork; S2 pre-buried pipe: locate the anchor hole and drill the positioning hole, insert the front end of the pre-buried pipe into the positioning hole, and movably set a protective sleeve on the pre-buried pipe, and the rear part of the pre-buried pipe is located outside the soil; S3 Pre-buried pipe reinforcement: The pre-buried fixing parts are inserted into the soil, and the pre-buried fixing parts are provided with connectors connected to the protective sleeves on the pre-buried pipes; S4 spraying concrete: spray concrete in layers and lay steel mesh to form a concrete layer; S5: Remove the embedded pipes: remove the embedded pipes, demould the embedded pipes from the protective sleeves, and form embedded openings on the concrete layer; S6 liner casing production: standard sections are produced in sections, and the standard sections are spliced ​​to form the liner casing; S7 casing installation: There are multiple grouting holes on the sleeve, and a liner sleeve is inserted into the sleeve. The casing and the drilling rig simultaneously open anchor holes in the embedded opening toward the soil. After the drilling is completed, the liner sleeve is removed; S8 liner casing secondary installation: Install a sealing plug on one end of the liner casing inserted into the anchor hole, and install the liner casing into the sleeve for the second time; S9 Anchor installation: The anchor is installed into the sleeve, and the front end of the anchor passes through the sealing plug; S10 Pulling out the liner casing: Pull out the liner casing in sections according to the design, and remove the liner casing from the soil. After pulling out, perform pressure grouting. During pressure grouting, the slurry penetrates into the soil through the grouting holes. Repeat S10 for multiple times to pull out the liner casing and maintain pressure until the liner casing is completely pulled out of the soil; S11 waist beam installation: The waist beam is installed on the concrete slope, the anchor rod is connected to the waist beam, and then prestress is applied to the anchor rod; S12 Earthwork re-excavation: earthwork re-excavation is carried out after the upper support is completed; Repeat S2-S12 to support and excavate multiple layers of earth until the foundation pit support is completed.

2. The foundation pit support construction method under complex geological conditions according to claim 1 is characterized by: The inner liner sleeve (13) in S6 comprises a plurality of standard sections, the rear end of the standard section is an insertion end, the front end of the standard section is a socket end, the insertion end is provided with a thread, and the socket end is provided with a thread structure adapted to the insertion end. The plurality of standard sections are detachably connected to form the inner liner sleeve (13) by inserting the insertion end into the socket end.

3. The foundation pit support construction method under complex geological conditions according to claim 1 is characterized by: The embedded fixing member (11) in S3 comprises an embedded rod (111), an insertion rod (112) and a connecting rod (113); the front end of the embedded rod (111) is provided with an insertion rod (112) for inserting into the soil, and the rear end of the embedded rod (111) is provided with a connecting screw rod (113); The embedded rod (111) is provided with a transparent connection hole for connecting with a connecting piece; The length of the embedded rod (111) is greater than the thickness of the sprayed concrete layer.

4. The foundation pit support construction method under complex geological conditions according to claim 1, characterized in that: The sealing plug (14) in S9 comprises a mounting ring and a sealing ring, the width of the mounting ring is greater than the width of the sealing ring, the mounting ring is provided with a connecting hole for connecting to the liner sleeve (13), and the connecting hole is connected to the liner sleeve (13) by a bolt; The sealing ring is provided with an escape opening for the anchor rod to pass through.

5. The foundation pit support construction method under complex geological conditions according to any one of claims 1 to 4, characterized in that: The sleeve (12) in S7 is provided with a plurality of transparent slurry infiltration holes, the plurality of slurry infiltration holes are evenly spaced around the axis of the sleeve (12), each group of slurry infiltration holes comprises a plurality of slurry infiltration holes, and the slurry infiltration holes are evenly spaced along the extension direction of the sleeve (12).

6. The foundation pit support construction method under complex geological conditions according to any one of claims 1 to 4, characterized in that: The waist beam in S11 is detachably connected to the concrete layer via a connecting screw (113).

7. The foundation pit support construction method under complex geological conditions according to claim 6, characterized in that: The waist beam comprises two support beams (1), a plurality of connecting plates (2) and a connecting plate (3); the support beam (1) is provided with a connecting socket for the connecting screw (113) to pass through; the support beam (1) is arranged horizontally, and the two support beams (1) are located in corresponding positions up and down, and an installation gap is left between the two support beams (1); A plurality of connecting plates (2) are arranged on the support beam (1) at intervals on the left and right, the upper portion of the connecting plates (2) is welded to the outer surface of the support beam (1) located on the upper side, and the lower portion of the connecting plates (2) is welded to the outer surface of the support beam (1) located on the lower side; A connecting plate (3) is provided between two adjacent waist beams, and both left and right ends of the connecting plate (3) extend into the installation gap on the waist beam on the same side. The connecting plate (3) is detachably connected to the two support beams (1) on the same side.

8. The foundation pit support construction method under complex geological conditions according to claim 7, characterized in that: The support beam (1) is provided with a vertically transparent plug hole, and a mounting rod (4) that can be extended vertically is provided between the two support beams (1), and the upper and lower ends of the mounting rod (4) are respectively plugged into adjacent plug holes; A connection socket (5) is provided on the connection plate (3), and the mounting rod (4) passes through the connection socket (5).

9. The foundation pit support construction method under complex geological conditions according to claim 8, characterized in that: The mounting rod (4) comprises a sleeve (401) and a screw (402); the sleeve (401) is inserted between two upper and lower adjacent insertion holes; the upper end of the sleeve (401) is fixedly connected to a limit plate; the width of the limit plate is greater than the diameter of the connection insertion hole; a threaded connection groove with a lower opening is provided in the sleeve (401); the screw (402) is threadedly connected in the threaded connection groove; the lower end of the screw (402) is fixedly connected to a limit block; the width of the limit block is greater than the diameter of the connection insertion hole.

10. The foundation pit support construction method under complex geological conditions according to any one of claims 7 to 9, characterized in that: The front side of the support beam (1) is detachably connected to a mounting plate (6) by bolts, a pad (7) is fixedly connected to the mounting plate (6), the pad (7) has an inclination adapted to the anchor rod, a front-to-back transparent avoidance hole is opened on the pad (7), the avoidance hole corresponds to the position of the mounting gap front-to-back, an anchor (8) is fixedly connected to the pad (7), and the front end of the anchor cable passes through the mounting gap and the avoidance hole and is fixedly connected to the anchor (8).

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