A foundation pit retaining structure under a weathered rock geological layer restricted space and a construction method thereof

Abstract

The application discloses a foundation pit retaining structure under a weathered rock geological layer in a limited space and a construction method thereof, and relates to the technical field of foundation pit retaining structures. The method comprises the following steps: providing a Larsen steel sheet pile; performing hole guiding construction to form a foundation pit retaining hole; and filling construction with backfill materials, wherein the backfill materials below a foundation pit excavation bottom line are cement mortar mixed with fibers, and the backfill materials above the foundation pit excavation bottom line are undisturbed soil removed by the hole guiding construction; inserting the Larsen steel sheet pile, embedding the Larsen steel sheet pile on both sides by the backfill materials below the foundation pit excavation bottom line, and extruding and fixing the Larsen steel sheet pile on both sides by the backfill materials above the foundation pit excavation bottom line; performing pressurized grouting through a grouting pipe on the Larsen steel sheet pile to form a horizontal water stop curtain; and forming the foundation pit retaining structure of a board wall water stop composite structure through the foundation pit retaining hole, the backfill materials, the Larsen steel sheet pile and the water stop curtain. The application can construct the foundation pit retaining structure under the condition that the operation space is limited, and has the advantages of good water stopping effect and high safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit retaining engineering, and particularly relates to a foundation pit retaining structure under a confined space of a weathered rock geological layer and a construction method thereof. BACKGROUND

[0002] In traditional underground engineering construction, deep foundation pit construction needs to be performed first with support structure construction such as retaining structure and support, and then with slope excavation. In deep foundation pit construction adjacent to existing structures, both the safety in the construction process of the bid section and the safety influence of the foundation pit excavation on the existing structures need to be considered. When the bid section foundation pit is close to the adjacent existing structures, the deep foundation pit construction of the bid section does not have enough operation space for the working surface of support and slope excavation construction. Since the net spacing between bored piles and other engineering piles is small, there is no operation space for construction of large-diameter engineering piles as foundation pit retaining structures. Therefore, how to construct the foundation pit retaining structure under the condition of limited operation space due to small distance from the adjacent existing structures becomes a problem to be solved in the field. SUMMARY

[0003] The present application aims to provide a foundation pit retaining structure under a confined space of a weathered rock geological layer and a construction method thereof, so as to solve the problem of inability to construct the foundation pit retaining structure under the condition of limited operation space due to small distance from the adjacent existing structures.

[0004] To solve the above technical problem, the present application provides a construction method of a foundation pit retaining structure under a confined space of a weathered rock geological layer, comprising:

[0005] Larssen steel sheet piles provided with grouting pipes are provided, so that the grouting pipes are distributed on both sides of the Larssen steel sheet piles;

[0006] A hole drilling construction is performed along the foundation pit boundary line downward through the weathered rock geological layer to form a foundation pit retaining hole;

[0007] Backfill material filling construction is performed in the foundation pit retaining hole, wherein the backfill material below the foundation pit excavation bottom line is cement mortar doped with fibers, and the backfill material above the foundation pit excavation bottom line is undisturbed soil taken out by the hole drilling construction;

[0008] The Larssen steel sheet piles provided with grouting pipes on both sides are inserted into the backfill material to the bottom of the foundation pit retaining hole, so that the backfill material is distributed on both sides of the Larssen steel sheet piles, the Larssen steel sheet piles are embedded on both sides by the backfill material below the foundation pit excavation bottom line, and the Larssen steel sheet piles are extruded and fixed on both sides by the backfill material above the foundation pit excavation bottom line;

[0009] The method comprises the following steps: forming a horizontal waterproof curtain in the soil layer below the bottom of the foundation pit retaining hole by pressurized grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile through a grouting pipe; and forming a composite structure of the foundation pit retaining structure of the sheet-pile waterproof by the foundation pit retaining hole, the backfill material, the Larsen steel sheet pile and the waterproof curtain.

[0010] Further, the application provides a construction method of the foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein a rotary excavator or a drilling machine is used to drill a hole through the weathered rock geological layer to perform hole guiding construction to form the foundation pit retaining hole.

[0011] Further, the application provides a construction method of the foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein a plurality of horizontal steels are vertically and spacedly welded on the concave surface of the Larsen steel sheet pile before the Larsen steel sheet pile is inserted, and the horizontal steels on the adjacent concave surfaces of the inner and outer sides of the Larsen steel sheet pile are distributed staggeredly.

[0012] Further, the application provides a construction method of the foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein cement and yellow sand are mixed at a ratio of 1:1, and 1% of fibers are added to form cement mortar doped with fibers.

[0013] Further, the application provides a construction method of the foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein cement-based permeable crystalline cement slurry is used to perform pressurized grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile through a grouting pipe.

[0014] Further, the application provides a construction method of the foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein the foundation pit retaining hole, the backfill material, the Larsen steel sheet pile and the horizontal waterproof curtain are constructed along the foundation pit boundary line in sections.

[0015] To solve the above technical problems, the application further provides a foundation pit retaining structure under the weathered rock geological layer in a limited space, comprising a foundation pit retaining hole constructed downward through the weathered rock geological layer along the foundation pit boundary line, a Larsen steel sheet pile inserted into the foundation pit retaining hole, a backfill material filled in the foundation pit retaining hole and distributed on the two sides of the Larsen steel sheet pile, a fixed end of the Larsen steel sheet pile formed by the backfill material doped with fibers and embedded on the two sides of the Larsen steel sheet pile below the bottom line of the foundation pit excavation, a free end of the Larsen steel sheet pile formed by the backfill material in the original state and pressed and fixed on the two sides of the Larsen steel sheet pile above the bottom line of the foundation pit excavation, a horizontal waterproof curtain formed in the soil layer below the bottom of the foundation pit retaining hole by pressurized grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile through a grouting pipe inserted into the foundation pit retaining hole, and a composite structure of the sheet-pile waterproof formed by the foundation pit retaining hole, the backfill material, the Larsen steel sheet pile and the horizontal waterproof curtain.

[0016] Further, the application provides a foundation pit retaining structure under the weathered rock geological layer in a limited space, wherein a plurality of horizontal steels are vertically and spacedly welded on each concave surface of the Larsen steel sheet pile.

[0017] Further, the application provides the foundation pit retaining structure under the limited space of the weathered rock geological layer, and the horizontal steel bars of the adjacent concave surfaces on the inner and outer sides of the Larsen steel sheet pile are distributed staggeredly.

[0018] Further, the application provides the foundation pit retaining structure under the limited space of the weathered rock geological layer, and the grouting pipes are arranged on at least part of the concave surfaces on the inner and outer sides of the Larsen steel sheet pile along the height thereof.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] The foundation pit retaining structure under the limited space of the weathered rock geological layer and the construction method thereof provided by the application have the following advantages: the hole retaining hole is formed through hole drilling construction, the backfill material is filled in the hole retaining hole, and the Larsen steel sheet pile is inserted into the hole retaining hole; the backfill material located below the bottom line of the foundation pit excavation is used as the cement mortar mixed with fibers to embed and fix the Larsen steel sheet pile on both sides, so that the deformation resistance of the Larsen steel sheet pile is improved; the backfill material located above the bottom line of the foundation pit excavation is used as the undisturbed soil to extrude and fix the Larsen steel sheet pile on both sides, so that the Larsen steel sheet pile is prevented from deviating or deforming due to the disturbance of the undisturbed soil caused by hole drilling of adjacent sections or due to collision and the like; the backfill material in the hole retaining hole and the panel wall composite structure formed by the Larsen steel sheet pile are used to stably fix the Larsen steel sheet pile in the hole retaining hole, so that the stability of the foundation pit retaining structure is improved, the stress safety of the foundation pit is ensured, and the problem that the foundation pit retaining structure cannot be constructed under the condition that the operation space is limited due to the small distance from the adjacent existing structure is solved; the fibers in the cement mortar can be solidified together with the underground water to stabilize the Larsen steel sheet pile, and the fibers can strengthen the toughness, improve the early solidified body strength, effectively transfer and disperse stress, and thus reduce the generation and expansion of cracks.

[0021] The foundation pit retaining structure under the limited space of the weathered rock geological layer and the construction method thereof provided by the application have the following advantages: the horizontal waterproof curtain is constructed at the bottom of the hole retaining hole, so that the underground water is prevented from penetrating above the bottom line of the foundation pit excavation; the backfill material located below the bottom line of the foundation pit excavation is used as the cement mortar mixed with fibers to embed and fix the Larsen steel sheet pile on both sides, so that the vertical waterproof curtain is formed on both sides of the Larsen steel sheet pile, and the problem of underground water leakage of the retaining system caused by construction is solved, and high-quality conditions are provided for the construction of the basement structure in the later period; the hole retaining hole, the backfill material, the Larsen steel sheet pile and the waterproof curtain form the panel wall waterproof composite structure of the foundation pit retaining structure, the stress performance of the foundation pit retaining structure is improved, and the three-side waterproof effect of the foundation pit retaining structure is improved.

[0022] The weathered rock geological layer limited space under the foundation pit retaining structure and the construction method thereof can solve the problem of deep foundation pit retaining engineering without traditional supporting and slope excavation in the limited operation space, and can construct the high-strength and low-deformation foundation pit retaining structure system in a short time, so as to avoid the risk of collapse caused by long-term exposure of the foundation pit without retaining structure. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flow chart of the construction method of the foundation pit retaining structure under the weathered rock geological layer limited space;

[0024] Figure 2 is a plane structure schematic diagram of the Larsen steel sheet pile provided with a grouting pipe and horizontal reinforcement;

[0025] Figure 3 is a plane structure schematic diagram of the foundation pit retaining hole;

[0026] Figure 4 is a plane structure schematic diagram of filling the backfill material in the foundation pit retaining hole;

[0027] Figure 5 is a plane structure schematic diagram of the foundation pit retaining structure under the weathered rock geological layer limited space;

[0028] Figure 6 is Figure 5 the cross-sectional structure schematic diagram of A-A in

[0029] Figure 7 is Figure 5 the cross-sectional structure schematic diagram of B-B in

[0030] The drawings shown in the figure are:

[0031] 100, foundation pit retaining structure, 110, foundation pit retaining hole, 111, foundation pit excavation bottom line, 120, backfill material, 121, free end, 122, embedded end, 130, Larsen steel sheet pile, 131, grouting pipe, 132, horizontal reinforcement, 140, horizontal waterproof curtain. DETAILED DESCRIPTION

[0032] The present application will be described in detail below with reference to the accompanying drawings: According to the following description, the advantages and characteristics of the present application will be more clear. It should be noted that the drawings are very simplified and use non-precise proportions, only to facilitate, clear and assist the purpose of explaining the embodiments of the present application.

[0033] Please refer to Figures 5 to 7The embodiment of the present application provides a foundation pit retaining structure 100 under the limited space of weathered rock geological layer, which comprises a foundation pit retaining hole 110 constructed downward along the foundation pit boundary line through the weathered rock geological layer, a Larsen steel sheet pile 130 inserted into the foundation pit retaining hole 110, backfill material 120 filled in the foundation pit retaining hole 110 and distributed on both sides of the Larsen steel sheet pile 130, a fixed end 122 formed by the cement mortar mixed with fibers on both sides of the Larsen steel sheet pile 130 below the foundation pit excavation bottom line, a free end 121 formed by the undisturbed soil on both sides of the Larsen steel sheet pile 130 above the foundation pit excavation bottom line, a horizontal waterproof curtain 140 formed in the soil layer below the bottom of the foundation pit retaining hole 110 by pressure grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile 130 through the grouting pipe 131 inserted into the foundation pit retaining hole 110, and the foundation pit retaining hole 110, the backfill material 120, the Larsen steel sheet pile 130 and the horizontal waterproof curtain 140 form a composite structure of sheet pile waterproof.

[0034] Please refer to Figure 5 The foundation pit retaining structure 100 under the limited space of weathered rock geological layer provided by the embodiment of the present application is characterized in that a plurality of horizontal steel bars 132 are vertically and spacedly welded on each concave surface of the Larsen steel sheet pile 130. In order to improve the fixing effect with the backfill material, each horizontal steel bar 132 on each concave surface can be two parallel rows, wherein the horizontal steel bars 132 can be welded by using the waste steel bars on the construction site, which meets the requirement of green construction "material saving" and reduces a large amount of waste steel treatment and promotes the recycling of resources. Alternatively, the horizontal steel bars 132 can be replaced by pegs to improve the fixing effect of the Larsen steel sheet pile 130 with the backfill material 120. In order to improve the effect of balanced fixing, the horizontal steel bars 132 of adjacent concave surfaces on the inner and outer sides of the Larsen steel sheet pile 130 can be distributed staggeredly.

[0035] Please refer to Figure 5 In order to construct the horizontal waterproof curtain 140 in the soil layer below the bottom of the foundation pit retaining hole 110, the foundation pit retaining structure 100 under the limited space of weathered rock geological layer provided by the embodiment of the present application is characterized in that grouting pipes 131 are arranged on at least part of the concave surfaces on the inner and outer sides of the Larsen steel sheet pile 130 along the height thereof.

[0036] Please refer to Figures 1 to 7 The embodiment of the present application provides a construction method of the foundation pit retaining structure 100 under the limited space of weathered rock geological layer, which can comprise the following steps:

[0037] Step 201, providing a Larsen steel sheet pile 130 provided with a grouting pipe 131, so that the grouting pipe 131 is distributed on both sides of the Larsen steel sheet pile 130. The grouting pipe 131 can be arranged in at least part of the concave surfaces of the Larsen steel sheet pile 130.

[0038] Step 202, along the foundation pit boundary line down through the weathered rock geological layer and other hard geological layer to form a foundation pit retaining hole 110. In order to improve the construction progress, the rotary excavator or drill can be used to drill through the weathered rock geological layer to form a foundation pit retaining hole 110.

[0039] Step 203, backfill material 120 filling construction is carried out in the foundation pit retaining hole 110, wherein the backfill material 120 below the foundation pit excavation bottom line is cement mortar mixed with fiber, and the backfill material 120 above the foundation pit excavation bottom line is undisturbed soil taken out by the hole drilling construction. The backfill material 120 can ensure the safety of the bid section during the foundation pit construction process and the stability of the adjacent existing structure.

[0040] Step 204, insert the Larsen steel sheet pile 130 with grouting pipe 131 installed on both sides into the bottom of the foundation pit retaining hole 110 in the backfill material 120, so that the backfill material 120 is distributed on both sides of the Larsen steel sheet pile 130, and the Larsen steel sheet pile 130 is embedded on both sides by the backfill material 120 below the foundation pit excavation bottom line, here forms an embedded end 122, which improves the stability, reliability and firmness of the Larsen steel sheet pile 130, and cement and yellow sand can be used in a ratio of 1:1 and mixed with 1% fiber to form cement mortar mixed with fiber, wherein the embedded end 122 is located in or passes through the medium weathered mixed rock layer or the strong weathered mixed rock layer; the Larsen steel sheet pile 130 is fixed by extrusion on both sides by the backfill material 120 above the foundation pit excavation bottom line, here forms a free end 121. Before inserting the Larsen steel sheet pile 130, a plurality of horizontal steel bars 132 can be vertically and spacedly welded on the concave surface of the Larsen steel sheet pile 130, and the horizontal steel bars 132 on the adjacent concave surfaces inside and outside the Larsen steel sheet pile 130 are distributed staggered, for example, 50% staggered and balanced distribution. The horizontal steel bars 132 enhance the contact surface with the backfill material 120, reduce the lateral displacement, and improve the fixing effect of the Larsen steel sheet pile 130.

[0041] Step 205, pressure grouting is carried out from the water-facing surface to the backwater surface of the Larsen steel sheet pile 130 through the grouting pipe 131, a horizontal waterproof curtain 140 is formed in the soil layer below the bottom of the foundation pit retaining hole 110, and the foundation pit retaining structure 100 of the composite structure of the sheet pile waterproof is formed by the foundation pit retaining hole 110, the backfill material 120, the Larsen steel sheet pile 130 and the waterproof curtain. Cement-based permeable crystalline cement slurry can be used to carry out pressure grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile 130 through the grouting pipe 131, to fill the pore and crack channels by pressure, and form the horizontal waterproof curtain 140.

[0042] In order to ensure construction safety and pit stability, the construction method of the pit retaining structure 100 under the limited space of the weathered rock geological layer provided by the embodiment of the present application, the pit retaining hole 110, the backfill material 120, the Larsen steel sheet pile 130 and the horizontal waterproof curtain 140 are constructed along the pit boundary line in sections, for example, 5m per section.

[0043] The pit retaining structure 100 under the limited space of the weathered rock geological layer and the construction method thereof provided by the embodiment of the present application, the pit retaining hole 110 is formed by the hole drilling construction, the backfill material 120 is filled in the pit retaining hole 110, and the Larsen steel sheet pile 130 is inserted in the pit retaining hole 110, the backfill material 120 located below the pit excavation bottom line is used as the cement mortar doped with fibers to embed the Larsen steel sheet pile 130 on both sides, so as to improve the deformation resistance of the Larsen steel sheet pile 130, the backfill material 120 located above the pit excavation bottom line is used as the undisturbed soil to extrude and fix the Larsen steel sheet pile 130 on both sides, so as to prevent the Larsen steel sheet pile 130 from deviating or deforming due to the disturbance of the undisturbed soil caused by the hole drilling of the adjacent section or due to the collision and the like, the backfill material 120 in the pit retaining hole 110 and the Larsen steel sheet pile 130 form a panel wall composite structure, so as to stably fix the Larsen steel sheet pile 130 in the pit retaining hole 110, strengthen the stability of the retaining system, ensure the safety of the pit stress, and solve the problem that the pit retaining structure 100 cannot be constructed under the condition that the operation space is limited due to the small distance from the adjacent existing structure. The fibers in the cement mortar can be solidified together with the underground water, stabilize the Larsen steel sheet pile 130, the fibers can also strengthen the toughness, improve the early solidified body strength, can effectively transfer and disperse stress, so as to reduce the generation and expansion of cracks.

[0044] The pit retaining structure 100 under the limited space of the weathered rock geological layer and the construction method thereof provided by the embodiment of the present application, the horizontal waterproof curtain 140 is constructed at the bottom of the pit retaining hole 110, so as to prevent the underground water from penetrating above the pit excavation bottom line, the backfill material 120 located below the pit excavation bottom line is used as the cement mortar doped with fibers to embed the Larsen steel sheet pile 130 on both sides, so as to form the vertical waterproof curtain located on both sides of the Larsen steel sheet pile 130, thereby solving the problem of underground water leakage of the retaining system due to construction, and providing high-quality conditions for the construction of the basement structure in the later period. The pit retaining structure 100 forms a panel wall waterproof composite structure by the pit retaining hole 110, the backfill material 120, the Larsen steel sheet pile 130 and the waterproof curtain, improves the stress performance of the pit retaining structure 100, and improves the three-side waterproof effect of the pit retaining structure 100.

[0045] The base pit enclosure structure 100 and the construction method thereof under the weathered rock geological layer limited space provided by the embodiment of the present application can solve the deep base pit enclosure engineering without traditional supporting and slope excavation under the limited operation space, can construct the high-strength and low-deformation base pit enclosure structure 100 system in a short time, thereby avoiding the risk of collapse caused by long-time exposure of the base pit without the enclosure structure.

[0046] The base pit enclosure structure 100 and the construction method thereof under the weathered rock geological layer limited space provided by the embodiment of the present application can solve the deep base pit enclosure structure 100 construction difficulty under the complex geological environment, can guarantee the smooth construction of the underground engineering, and protect the construction progress and construction quality. The base pit enclosure structure 100 shown in the figure is constructed in the geological layer from top to bottom: miscellaneous fill, hard cohesive soil, fully weathered mixed rock, strongly weathered mixed rock (soil), strongly weathered mixed rock (block), moderately weathered mixed rock, and slightly weathered mixed rock. However, it is not limited to the construction of the weathered rock geological layer, and can be applied to the construction of other hard geological layers.

[0047] The present application is not limited to the above specific embodiments. Obviously, the above-described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application. Those skilled in the art can make other levels of modifications and changes to the present application. Thus, if these modifications and changes of the present application belong to the scope of the claims of the present application, the present application also intends to include these modifications and changes.

Claims

1. A construction method of a foundation pit retaining structure in a confined space under a weathered rock geological layer, characterized by, The application relates to a kind of composite structure of retaining wall water stop. Providing the Larsen steel sheet pile installed with grouting pipe, distributing the grouting pipe on both sides of the Larsen steel sheet pile, welding multiple horizontal steels on the concave surface of the Larsen steel sheet pile vertically and spacedly before inserting the Larsen steel sheet pile, and distributing the horizontal steels of adjacent concave surfaces on both sides of the Larsen steel sheet pile staggeredly; Drilling hole construction along the foundation pit boundary line to form a foundation pit retaining hole; Backfill material filling construction in the foundation pit retaining hole, wherein the backfill material below the foundation pit excavation bottom line is cement mortar mixed with fibers, and the backfill material above the foundation pit excavation bottom line is undisturbed soil obtained by drilling hole construction; Inserting the Larsen steel sheet pile with grouting pipe on both sides into the backfill material to the bottom of the foundation pit retaining hole, distributing the backfill material on both sides of the Larsen steel sheet pile, embedding the Larsen steel sheet pile by the backfill material below the foundation pit excavation bottom line, and extruding and fixing the Larsen steel sheet pile by the backfill material above the foundation pit excavation bottom line; Pressurized grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile through the grouting pipe to form a horizontal water stop curtain in the soil layer below the bottom of the foundation pit retaining hole, and forming a foundation pit retaining structure of plate wall water stop composite structure by the foundation pit retaining hole, the backfill material, the Larsen steel sheet pile and the water stop curtain.

2. The construction method of a foundation pit retaining structure under a weathered rock geological layer restricted space according to claim 1, characterized in that, Drilling hole construction by using a rotary excavator or a drill to drill soil through the weathered rock geological layer to form a foundation pit retaining hole.

3. The construction method of a foundation pit retaining structure under a weathered rock geological layer restricted space according to claim 1, characterized in that, Mixing cement and yellow sand at a ratio of 1:1 and adding 1% of fibers to form cement mortar mixed with fibers.

4. The construction method of a foundation pit retaining structure under a weathered rock geological layer restricted space according to claim 1, characterized in that, Pressurized grouting of cement-based permeable crystalline cement slurry from the water-facing surface to the backwater surface of the Larsen steel sheet pile through the grouting pipe.

5. The construction method of a foundation pit retaining structure under a weathered rock geological layer restricted space according to claim 1, characterized in that, Segmented construction of the drilling hole, the backfill material, the Larsen steel sheet pile and the grouting along the foundation pit boundary line.

6. A foundation pit retaining structure under a confined space of a weathered rock geological layer, characterized in that, The application relates to a kind of composite structure of retaining wall water stop. Providing the Larsen steel sheet pile installed with grouting pipe, distributing the grouting pipe on both sides of the Larsen steel sheet pile, welding multiple horizontal steels on the concave surface of the Larsen steel sheet pile vertically and spacedly before inserting the Larsen steel sheet pile, and distributing the horizontal steels of adjacent concave surfaces on both sides of the Larsen steel sheet pile staggeredly; Drilling hole construction along the foundation pit boundary line to form a foundation pit retaining hole; Backfill material filling construction in the foundation pit retaining hole, wherein the backfill material below the foundation pit excavation bottom line is cement mortar mixed with fibers, and the backfill material above the foundation pit excavation bottom line is undisturbed soil obtained by drilling hole construction; Inserting the Larsen steel sheet pile with grouting pipe on both sides into the backfill material to the bottom of the foundation pit retaining hole, distributing the backfill material on both sides of the Larsen steel sheet pile, embedding the Larsen steel sheet pile by the backfill material below the foundation pit excavation bottom line, and extruding and fixing the Larsen steel sheet pile by the backfill material above the foundation pit excavation bottom line; Pressurized grouting from the water-facing surface to the backwater surface of the Larsen steel sheet pile through the grouting pipe to form a horizontal water stop curtain in the soil layer below the bottom of the foundation pit retaining hole, and forming a foundation pit retaining structure of plate wall water stop composite structure by the foundation pit retaining hole, the backfill material, the Larsen steel sheet pile and the water stop curtain. Drilling hole construction by using a rotary excavator or a drill to drill soil through the weathered rock geological layer to form a foundation pit retaining hole. Mixing cement and yellow sand at a ratio of 1:1 and adding 1% of fibers to form cement mortar mixed with fibers. Pressurized grouting of cement-based permeable crystalline cement slurry from the water-facing surface to the backwater surface of the Larsen steel sheet pile through the grouting pipe. Segmented construction of the drilling hole, the backfill material, the Larsen steel sheet pile and the grouting along the foundation pit boundary line. The application relates to a kind of composite structure of retaining wall water stop.

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