Construction method of a super-large landslide disaster drainage and anti-slide combined structure

Abstract

The application provides a construction method of a super-large landslide disaster drainage anti-sliding combined structure. The application is based on fluid mechanics, solid mechanics, a hydrodynamic model, a structure model and an engineering geological model, and studies a complete construction method of the drainage anti-sliding combined structure for super-large water-rich landslide disasters. Firstly, a small-diameter pile capable of being mechanized and quickly forming a hole is used to form a protection wall of the drainage anti-sliding structure in a circular arrangement; secondly, an internal prefabricated lining pipe piece is made and installed, a water-permeable hole and a drainage flower pipe are preset on the surface of the pipe piece; then, a reinforced concrete anti-sliding key is additionally arranged near a sliding surface; finally, a multi-branch directional drilling process is used to combine an upwardly inclined drainage pipe with the drainage anti-sliding structure to form a seepage-collecting-draining anti-sliding combined three-dimensional structure system. The application belongs to the technical field of geological disaster prevention and safety, specifically relates to light small-diameter pile treatment, non-excavation directional drilling and other technologies, and can be widely applied to the rapid treatment of super-large water-rich landslide disasters that are about to lose stability and deform or are deforming.

Description

Technical Field

[0001] This invention, based on fluid mechanics, solid mechanics, hydrodynamic models, structural models, and engineering geological models, studies a complete construction method for a combined drainage and anti-slide structure for massive water-rich landslides. First, small-diameter piles, which can be rapidly drilled using mechanized methods, are arranged in a circular pattern to form the retaining wall of the drainage and anti-slide structure. Second, prefabricated lining segments are fabricated and installed, with permeable holes and drainage perforations pre-set on the surface of the segments. Then, reinforced concrete anti-slide keys are added near the sliding surface. Finally, using multi-branch directional drilling technology, the inclined drainage pipes are combined with the drainage and anti-slide structure to form a three-dimensional "infiltration-collection-drainage" anti-slide combined structure system. This invention belongs to the field of geological disaster prevention and safety technology, specifically involving lightweight small-diameter pile treatment and trenchless directional drilling technologies, and can be widely applied to the rapid treatment of massive water-rich landslides that are about to become unstable or are already deforming. Background Technology

[0002] While traditional anti-slide piles improve the anti-slide stability of large landslides, their large cross-sectional area often reduces the seepage channels of water inside the slope, which may raise the water level of the landslide body, increase its self-weight, and reduce the cohesion and internal friction angle of the landslide body and the sliding bed, thus reducing landslide stability. Inspired by this, anti-slide piles with both drainage and anti-slide functions have become a research hotspot in recent years and a new technology that has received continuous attention from disciplines such as geological engineering, civil engineering, and hydraulic engineering. Various types of drainage anti-slide piles have been proposed, such as anti-liquefaction piles, hollow drainage anti-slide piles, box-type drainage anti-slide piles, and water-cutting and diversion pile-slab walls. This technology has gradually become a promising new and practical technology.

[0003] However, the application of drainage and anti-slide technology is not common at present. The long construction period, complex construction procedures and high construction difficulty are among the unfavorable factors that restrict the further promotion and popularization of drainage and anti-slide technology, especially its application in the treatment of major landslide disasters.

[0004] Therefore, there is an urgent need to study a highly mechanized construction technology that can be used for rapid construction in extremely large water-rich landslides and is easy to manufacture and assemble on-site.

[0005] The prevention and control of high-level debris flows has significant social and economic value. High-level debris flows are characterized by their continuous and chain-like nature. If not dealt with promptly, they can easily shovel and form higher-energy, larger-volume debris flows and mudslides, and even create landslide dams, posing a much greater threat. Summary of the Invention

[0006] This invention differs from existing drainage and anti-slide pile construction methods, breaking away from the traditional construction approach that prioritizes the anti-slide pile body while using drainage as a secondary element. Utilizing a combined three-dimensional structural system concept, it proposes a construction method based on lightweight structures, trenchless directional drilling, and prefabricated assembly structures. The construction of the anti-slide and drainage structures can be carried out simultaneously and in coordination, enhancing the stability of the structural system.

[0007] The objectives of this invention and the technical problems it solves can be achieved through the following technical solutions.

[0008] The present invention relates to the main structure as shown in the appendix. Figure 1-3 As shown.

[0009] Firstly, the construction of small-diameter pile groups (according to the "Code for Design of Landslide Prevention" (GBT 38509-2020), the diameter of a single pile should not exceed 500mm to be considered a small-diameter pile; see details) Figure 1 For silt deposits or landslides, single pile excavation uses casing drilling, with a pile diameter d = 300–500 mm. The total number of piles in the group is n, calculated using the following formula:

[0010] n≥D / 1000 (1)

[0011] in:

[0012] D – Diameter of the “circular” ring, in mm. When D < 1000 mm, the structure involved in this invention is not recommended.

[0013] The pile group is arranged in a circular pattern with equal intervals s (see details). Figure 2 ), Calculation formula:

[0014] s=D×π / n (2)

[0015] The length of the bottom of the pile group that exceeds the sliding surface accounts for 1 / 3 of the total length L of the pile body.

[0016] Secondly, excavate the soil from top to bottom within the "circular" area to fabricate and install precast reinforced concrete lining segments with a segment thickness of d. g Water-permeable holes are pre-set on the lining segments on the squeezing side of the landslide front. The diameter of the water-permeable holes is 130-150mm. Radial water collection pipes with a length of about L=1-3m are excavated and installed outside the water-permeable holes.

[0017] Then, excavation proceeds to the vicinity of the slip surface, where reinforced concrete anti-slip keys are excavated and constructed. According to the "Code for Design of Landslide Prevention" (GBT38509-2020), anti-slip keys can be used alone or in combination with other anti-slip retaining structures in landslide control. This application focuses on the use of anti-slip keys, small-diameter pile groups, and drainage lining segments to form a combined structural system. Furthermore, the anti-slip force provided by the small-diameter pile group is R... fm Anti-slip key anti-slip force Rfk The combined landslide resistance is R. fcouple The corresponding calculation formula is as follows:

[0018] R fm =nτ fm =n([τ] ms A ms +[τ] mc A mc (3)

[0019] R fk =τ fk =([τ] ks A ks +[τ] kc A kc ) / cosα (4)

[0020] R fcouple =R fm +R fk +E p (5)

[0021] in:

[0022] n—the total number of the aforementioned small-diameter pile groups;

[0023] [τ] ms —Shear strength of steel in small-diameter piles;

[0024] A ms —Cross-sectional area of ​​reinforcement for a single small-diameter pile;

[0025] [τ] mc —Shear strength of concrete in a single small-diameter pile;

[0026] A mc —Cross-sectional area of ​​concrete in a single small-diameter pile;

[0027] [τ] ks —Shear strength of antislip key steel;

[0028] A ks —Cross-sectional area of ​​anti-slip key reinforcement;

[0029] [τ] kc —Shear strength of anti-slip key concrete;

[0030] A kc —Cross-sectional area of ​​the anti-slip key concrete;

[0031] α — the angle between the sliding surface and the horizontal line;

[0032] E p—The passive earth pressure borne by a single “circular” ring within its diameter (D-2d);

[0033] Finally, using a multi-branch directional drilling process, the inclined water collection pipe is connected to the drainage and anti-slip structural lining segments. Drilling continues, penetrating the lining to the bottom of the slope, and drilling holes to install drainage pipes outside the slope, forming a "seepage-collection-drainage" anti-slip combined three-dimensional structural system. The angle of the water collection pipe is equal to the angle of the sliding surface, both being α. The drainage capacity of the "seepage-collection-drainage" anti-slip combined three-dimensional structural system can be calculated using formula (6):

[0034]

[0035] in:

[0036] —Based on the overall permeability coefficient, the water collection pipe passes through layers of soil and rock i = 1, 2, 3, ..., m, with soil thickness h. i , K i Let be the permeability coefficient of the i-th layer of rock and soil;

[0037] H h —Comprehensive water level of a single "circle", H h = (H1+H2) / 2, where H1 and H2 are the distances from the front and rear sides of the "circular" ring to the top of the anti-slip key, see details. Figure 4 ;

[0038] H w —The distance from the highest water level in the slope to the top of the anti-slip key;

[0039] L—Length of the radial water collection pipe;

[0040] m — the number of radial water collection pipes;

[0041] b1—Equivalent drainage radius, when the radial water collection pipes L are of equal length. When the radial water collection pipes L are of unequal length L i Let be the length of the i-th water collection pipe;

[0042] b2—Maximum radius of influence, which in this invention refers to the shortest horizontal distance from the center of the "circular" circle to the highest water level within the slope.

[0043] This method is also applicable to small-diameter pile groups arranged in a "rectangular" pattern.

[0044] The main process of this method is shown in the appendix. Figure 5 As shown.

[0045] The process can be divided into the following four main steps: construction of lightweight structures with small-diameter pile groups that can be quickly and mechanically drilled; soil excavation and assembly of seepage-collection lining structures; construction of reinforced concrete anti-slip keys; and trenchless directional drilling construction of drainage pipes.

[0046] (1) Construction of lightweight structures with small-diameter pile groups that can be mechanically and quickly drilled

[0047] This invention, in order to provide a large-section drainage and anti-slide structure, departs from the ordinary anti-slide pile model of surface or built-in drainage channels, and instead adopts a combined structure drainage method. The specific steps are as follows: construction preparation → pile location surveying → drilling rig positioning and casing drilling → installation of steel reinforcement cage (I-beams, reinforcing positioning steel bars) → pouring fine stone concrete → casing insertion and grouting → casing extraction → formation of a "circular" retaining wall → construction of a connecting beam on top of the retaining wall pile.

[0048] (2) Soil excavation and assembly of seepage-collection lining structure

[0049] For the seepage-collection structure, this invention adopts a lining segment assembly mode, wherein the lining segments are pre-set with permeable holes. Specific steps: excavate soil within the "circular" area from top to bottom → install the initial reinforced concrete lining → install the secondary reinforced concrete lining → install the self-drilling water collection pipe, while taking care to pump out any water that has already seeped into the pit.

[0050] (3) Construction of reinforced concrete anti-slip keys

[0051] The anti-slip key proposed in this invention has a dual function: anti-slip and water collection at the bottom of the seepage-collection structure. Specific steps: excavation of soil → installation of formwork → binding of reinforcing steel → pouring of concrete.

[0052] (4) Trenchless directional drilling construction of drainage pipes

[0053] The drainage system of this invention utilizes trenchless directional drilling technology to connect inclined drainage pipes with drainage and anti-slip structural lining segments, forming a "seepage-collection-drainage" anti-slip combined three-dimensional structural system. Specific steps include: construction preparation → surveying and marking drilling rig positions → placing the positioning instrument → drilling rig guidance and control → drilling → connecting and connecting with the seepage-collection lining structure, drilling holes to install water inlet collection pipes → bottom drill rod penetrating the lining to the bottom of the slope, drilling holes to install external drainage pipes.

[0054] Compared with the prior art, the present invention has the following obvious advantages and beneficial effects:

[0055] Firstly, compared to traditional anti-slide pile models that rely on surface or internal drainage channels and construction approaches that prioritize the pile body while using drainage as a secondary element, this invention places equal importance on the "infiltration-collection-drainage" system and the anti-slide structure, considering them holistically. Utilizing advanced small-diameter pile group lightweight structures, trenchless directional drilling methods, and prefabricated assembly structures, the construction of the anti-slide system and the "infiltration-collection-drainage" system drainage structure can be carried out simultaneously and in tandem, enhancing the stability and safety of the structural system.

[0056] Secondly, the structure and method proposed in this invention are not simply a superposition of drainage and anti-slip capabilities; in fact, the anti-slip capability is superior to that of the superimposed individual components. The drainage capacity of the "circular" ring in the "infiltration-collection-drainage" system can be fully quantified and optimized.

[0057] Finally, the construction method proposed in this invention has clear steps, a well-defined structural mechanics concept, and easy-to-monitor drainage effect, which is conducive to its application and promotion. Attached Figure Description

[0058] Figure 1 Schematic diagram of drainage and anti-sliding combined structure for major landslide disasters

[0059] Figure 2 Cross-sectional view of the combined drainage and anti-sliding structure for major landslide disasters

[0060] Figure 3 Detailed longitudinal section of the drainage and anti-sliding composite structure for major landslide disasters

[0061] Figure 4 Calculation of the stability flow diagram of the drainage and anti-sliding combined structure for major landslide disasters

[0062] Figure 5 Construction Flowchart

[0063] 10-Water collection well, 11-Permeable backfill, 12-Reinforced concrete secondary lining, 13-Connecting beam, 14-Anti-slip key, 15-Drainage pipe, 16-Landslide, 17-Slip surface, 18-Trenchless directional drilling rig, 19-Drill rod, 20-Drilling rig, 21-Reinforced concrete primary lining, 22-Permeable hole, 23-Water collection flower pipe. Detailed Implementation

[0064] Based on the above description, the following is a specific implementation process, but the scope of protection of this patent is not limited to this implementation process.

[0065] Example: A massive landslide has a long, narrow shape in plan, with a maximum length of 1500m along the sliding direction. The landslide body is narrower at the top and wider at the bottom, with an average width of 240-530m, averaging 385m, and an area of ​​50×10. 4 m 2 The average thickness of the sliding body is approximately 40m, and the total volume is 2120×10.4 m 3 It is a deep, extra-large sedimentary landslide, and the landslide area is rich in groundwater.

[0066] The specific construction steps are as follows:

[0067] Step 1: Construction of Lightweight Structure with Small-Diameter Pile Groups

[0068] Construction preparation and site leveling were carried out. After site leveling, pile positions were marked out. A small-diameter pile group with a single pile diameter of Φ300mm was adopted, and φ320mm full-hole casing with a thickness of 8mm was used for drilling. After drilling to the designed depth of 60m, pile depth was measured, and I-beams and reinforcing bars were fabricated and installed, followed by pouring C30 pile core concrete. The small-diameter pile group was arranged in a circular, equally spaced pattern with a radius of 4m, and there were 8 small-diameter piles in total. Due to severe borehole collapse and even partial breakage of the casing during the pipe-fed drilling and extraction process, welded casing drilling was adopted in this step, and the casing was not extracted.

[0069] After the concrete reaches the design strength, the connecting beam is excavated and the pile heads are broken. Then, the connecting beam reinforcement and embedded parts are fabricated and installed, the connecting beam formwork is fabricated and installed, and the connecting beam concrete is poured in sequence.

[0070] Step 2: Soil excavation and assembly of seepage-collection lining structure

[0071] Excavation proceeds downwards along the circular retaining wall formed by the small-diameter pile group. At every 1000mm excavation depth, prefabricated linings are installed. The initial lining is typically 40cm thick, and the secondary lining is also 40cm thick. The initial lining uses C20 shotcrete. Before shotcreting, positioning reinforcement bars should be pre-installed to ensure the thickness of the shotcrete. The secondary lining uses prefabricated reinforced concrete lining segments. These segments have pre-set permeable holes, typically arranged in a quincunx pattern on the flow-facing side. The holes are externally wrapped with geotextile to prevent clogging. Self-drilling water collection pipes are installed outside the permeable holes, forming radial seepage holes 1-3m long. The water collection pipes inside the holes are lined with geotextile. The secondary lining segments have a trapezoidal cross-section with a short side of 200mm, a long side of 300mm, and a height of 1000mm for easy on-site assembly.

[0072] During the construction process, groundwater continuously seeped into the pit, so a water pump was used to continuously extract the seeping groundwater.

[0073] Step 3: Construction of reinforced concrete anti-slip key

[0074] Excavate the soil to near the slip surface (40m below ground level), fabricate formwork, tie reinforcing bars, and then pour C30 concrete. The anti-slip key is a cylinder and is integrally cast together with the small-diameter retaining pile group from step 1.

[0075] Step 4: Trenchless directional drilling construction of drainage pipes

[0076] A directional drilling rig is positioned at the lower part of the landslide. A positioning device is placed on the backslide side of the circular retaining wall of the small-diameter pile group. A guide control drill bit is installed on the drilling rig, followed by directional drilling with casing. The casing is made of polyethylene pipe with an inner diameter of φ100mm, and male and female threads are machined at both ends, with a single pipe length of 1200mm. When the drill bit reaches the circular retaining wall, it is connected to the seepage-collection lining structure.

[0077] The drill rod at the bottom continued drilling, penetrating the lining twice to the bottom of the slope, where a drainage pipe was installed outside the slope. The drainage pipe had an inner diameter of φ100mm and an angle α=10°.

Claims

1. A construction method for a combined drainage and anti-sliding structure for massive landslide disasters, characterized in that: First, the construction of small-diameter pile groups specifies that a single pile diameter of no more than 500mm is considered a small-diameter pile. For silt deposits or landslides, single pile excavation uses casing drilling, with a pile diameter d = 300–500mm. The total number of piles in the group is n, calculated using the following formula: n≥D / 1000 (1) in: D – Diameter of the "circle", in mm; The pile group is arranged in a circular pattern with equal intervals 's'. The calculation formula is as follows: s=D×π / n (2) The length of the bottom of the pile group exceeding the sliding surface accounts for 1 / 3 of the total pile length L; Secondly, excavate the soil from top to bottom within the "circular" area to fabricate and install precast reinforced concrete lining segments with a segment thickness of d. g Water-permeable holes are pre-set on the lining segments on the squeezing side of the landslide front. The diameter of the water-permeable holes is 130-150mm. Radial water collection pipes with a length of L=1-3m are excavated and installed outside the water-permeable holes. Then, excavate to the vicinity of the slip surface and excavate to construct reinforced concrete anti-slip keys; the anti-slip force provided by the small-diameter pile group is R. fm Anti-slip key anti-slip force R fk The combined landslide resistance is R. fcouple ; Corresponding calculation formula: R fm =nτ fm =n([τ] ms A ms +[t] mc A mc ) (3) R fk =t fk =([t] ks A ks +[t] kc A kc ) / cosα (4) R fcouple =R fm +R fk +E p (5) in: n—the total number of the aforementioned small-diameter pile groups; [τ] ms —Shear strength of steel in small-diameter piles; A ms —Cross-sectional area of ​​reinforcement for a single small-diameter pile; [τ] mc —Shear strength of concrete in a single small-diameter pile; A mc —Cross-sectional area of ​​concrete in a single small-diameter pile; [τ] ks —Shear strength of antislip key steel; A ks —Cross-sectional area of ​​anti-slip key reinforcement; [τ] kc —Shear strength of anti-slip key concrete; A kc —Cross-sectional area of ​​the anti-slip key concrete; α — the angle between the sliding surface and the horizontal line; E p —The passive earth pressure borne by a single "circular" ring within its diameter (D-2d); Finally, the inclined water collection pipe is connected to the drainage and anti-slip structure lining segments, and drilling continues to penetrate the lining to the bottom of the slope. Drill holes to install the drainage pipe outside the slope, forming a "seepage-collection-drainage" anti-slip combined three-dimensional structure system; the angle of the water collection pipe is equal to the angle of the sliding surface, both being α; the drainage capacity of the "seepage-collection-drainage" anti-slip combined three-dimensional structure system is calculated using formula (6): in: —Based on the overall permeability coefficient, the water collection pipe passes through layers of rock and soil i = 1, 2, 3, ..., m, with a soil thickness h. i , K i Let be the permeability coefficient of the i-th layer of rock and soil; H h —Comprehensive water level of a single "circle", H h = (H1+H2) / 2, where H1 and H2 are the distances from the front and rear sides of the "circular" ring to the top of the anti-slip key; H w —The distance from the highest water level in the slope to the top of the anti-slip key; L—Length of the radial water collection pipe; m — the number of radial water collection pipes; b1—Equivalent drainage radius, when the radial water collection pipes L are of equal length. When the radial water collection pipes L are of unequal length L i Let be the length of the i-th water collection pipe; b2—Maximum radius of influence, refers to the shortest horizontal distance from the center of the "circle" to the highest water level within the slope.

2. The construction method of a combined drainage and anti-sliding structure for a major landslide disaster according to claim 1, characterized in that, It consists of the following four steps: (1) Construction of lightweight structures with small-diameter pile groups that can be mechanically and quickly drilled The specific steps are as follows: construction preparation → pile position measurement → drilling rig positioning and casing drilling → steel reinforcement cage installation → fine stone concrete pouring → casing insertion and grouting → casing extraction → forming a "circular" retaining wall → construction of connecting beams on top of retaining wall piles. (2) Soil excavation and assembly of seepage-collection lining structure The method adopted is the assembly mode of lining segments, in which permeable holes are pre-set on the lining segments; the specific steps are: excavate the soil in the "circular" circle from top to bottom → install the primary reinforced concrete lining → install the secondary reinforced concrete lining → install the self-drilling water collection pipe, and pay attention to pumping out the water that has already seeped into the pit. (3) Construction of reinforced concrete anti-slip keys Excavation → Formwork installation → Reinforcing steel reinforcement → Concrete pouring; (4) Trenchless directional drilling construction of drainage pipes Specific steps: Construction preparation → Marking and setting out the drilling rig position → Placing the positioning instrument → Drilling rig guidance and control → Drilling the drill bit → Connecting and connecting with the seepage-collection lining structure, drilling holes to install water collection pipes for water inlet → The bottom drill rod penetrates the lining to the bottom of the slope, drilling holes to install drainage pipes outside the slope.

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