Landslide prevention and control structure units and systems, design methods and construction methods

Abstract

The present invention discloses a landslide prevention and control construction unit and system, design method and construction method. In order to solve the problem of prevention and control of high-steep and thick landslide bodies, the landslide prevention and control construction unit of the present invention is arranged within the front 1 / 3 of the landslide body, including an entrance tunnel and a side tunnel that are perpendicular to each other to form a T-shaped plane. The entrance tunnel opens on the slope surface and extends horizontally into the slope body to the sliding surface. The end of the entrance tunnel is connected to the side tunnel. Micro steel pipe piles are arranged in the side tunnel. The micro steel pipe piles extend upward into the landslide body and downward into the slope body below the sliding surface. The construction unit can be expanded into a landslide prevention and control construction system. The present invention also provides a design method and a construction method for the landslide prevention and control construction unit. The landslide prevention and control construction unit of the present invention combines the two technologies of the tunnel system and the micro steel pipe pile system. Both the construction structure itself and the construction method have the obvious advantage of small environmental deflection, and are particularly suitable for promotion and adoption in high-steep and thick landslide body prevention and control projects.

Description

Technical Field

[0001] The invention relates to a landslide prevention and control construction unit and system and a design method and a construction method thereof, and in particular to a landslide prevention and control construction unit for a high and steep slope with a landslide body thickness of not less than 50m, belonging to the field of mountain environmental disaster prevention and control engineering. Background Art

[0002] A high-steep slope with landslide risk and a landslide body thickness of not less than 50m can be referred to as a "high-steep and thick landslide body". Its accumulation body type is not limited to loose layer accumulation body, but also includes other accumulation body types such as rock layer and weak rock layer. This type of landslide body poses a greater threat to traffic buildings such as roads passing under it than general landslide bodies.

[0003] At present, active prevention and control engineering measures for landslide disasters include slope excavation, slope reinforcement, slope drainage, slope environmental protection, etc. Among them, slope reinforcement is a commonly used landslide control measure. Slope reinforcement generally uses retaining structures such as anti-slide pile wall systems to reinforce the landslide body to achieve the purpose of reducing the probability of landslides. However, in the prevention and control technology for high, steep and thick landslide bodies, when implementing common prevention and control engineering plans, there are usually problems such as difficulty in transporting equipment and materials, excessive excavation depth, and inability to accurately avoid huge hard rocks during construction.

[0004] Take the most commonly used anti-slide piles in existing landslide prevention and control structures as an example: anti-slide piles are commonly used slope reinforcement structures in active landslide disaster control technology. Their main structure is a pile-shaped structure that connects the upper and lower strata of the sliding surface. The main technical idea of ​​the anti-slide pile prevention and control scheme is to bury reinforced concrete piles at appropriate locations of the landslide body, with the lower end reaching a certain depth of the stable stratum below the sliding surface, to anchor the landslide body to prevent it from sliding downward and improve anti-slide stability. There are some defects in the application of anti-slide pile structure in high mountain canyon areas where there are high, steep and thick landslides: First, the construction problem. For the thick landslides in these areas, the anti-slide piles need to be very long, and the large excavation equipment and various materials are difficult to transport to the construction site. There may also be some huge hard blocks in the thick landslides that hinder the digging process, increasing the difficulty of the construction of traditional anti-slide piles; second, the safety problem. Due to the large hole depth required, the disturbance to the soil layer of the landslide body is large, and the risk of landslides during the excavation process also increases accordingly; third, the structural stability problem. Due to the increase in the length of the anti-slide piles, multiple sections of steel bars need to be welded to complete the entire structure, which reduces the toughness of the welds of the steel bar structure. Sectional pouring is also required during the pouring process, resulting in the overall performance of the anti-slide piles not being as good as one-time pouring. There may be internal breakage, and when the length of the anti-slide piles is too long, some of their benefits will be lost. Summary of the invention

[0005] The object of the present invention is to provide a single landslide prevention and control structure, a system, and their design and construction methods in view of the deficiencies of the prior art. This single landslide prevention and control structure can be better applied to the landslide prevention and control engineering conditions of high-steep and thick landslide bodies.

[0006] To achieve the above object, the present invention first provides a single landslide prevention and control structure, and its technical solution is as follows:

[0007] A single landslide prevention and control structure, characterized in that it is arranged within the first 1 / 3 range in front of the landslide body; it includes an entrance adit and a flank adit that are perpendicular to each other to form a T-shaped plane; the entrance adit opens on the slope surface and extends horizontally into the slope body to the sliding surface; the end of the entrance adit is connected to the flank adit, and a group of micro steel pipe piles are arranged in the flank adit; the group of micro steel pipe piles extends upward into the landslide body and downward into the slope body below the sliding surface.

[0008] The single landslide prevention and control structure of the present invention anchors the landslide body on the sliding surface by using a group of micro steel pipe piles that are respectively buried in the landslide body and the stable layer below the sliding surface up and down, which can provide sufficient anti-sliding force for the landslide body. And because the steel pipe piles are arranged at a position close to the sliding surface, the up and down extension lengths of the steel pipe piles are much smaller than the lengths of anti-slide piles driven from the top. The probability of encountering huge hard boulders and the drilling difficulty are reduced, and the number of welding times required for each steel pipe to meet the length requirements is greatly reduced. This not only reduces the construction difficulty and construction cost but also improves the overall performance of the steel pipe piles, so that the entire structural system achieves the purpose of safety, economy, speed, and efficiency.

[0009] In the single landslide prevention and control structure, the entrance adit extends from the slope surface into the mountain body (negative y-axis direction) to a position close to the sliding surface. The height of the adit can be as small as possible under the condition of meeting the equipment entry requirements, so as to reduce the disturbance to the soil mass (generally 2m - 4m), which is very beneficial for construction under the environmental conditions of high-steep and thick landslide bodies. The flank adit extends to both sides in the direction perpendicular to the entrance adit (x-axis direction). The purpose is to ensure that the adit position is close to the sliding surface, reduce the embedment depth of the group of steel pipe piles, and save manpower and material resources. This can also reduce construction disturbance and is beneficial for implementation under the environmental conditions of steep and thick landslide bodies.

[0010] Under the optimized technical solution, in the above single landslide prevention and control structure, the group of micro steel pipe piles can be arranged in two rows in a staggered pattern; there is a steel bar truss between the groups of micro steel pipe piles. Two groups of steel pipe piles are implanted in the cubic pile of concrete for the group of micro steel pipe piles. The latter group of steel pipe piles is close to the slope body, and the former group of steel pipe piles is close to the slope surface. The steel pipe pile includes an outer peripheral geological pipe, the lower part of the geological pipe is processed into a slotted pipe, the center of the geological pipe is a steel bar bundled in a staggered pattern, and mortar is poured between the geological pipe and the steel bar.

[0011] Furthermore, since a large part of the seepage water inside the landslide body will infiltrate toward the adit space with low pressure, which becomes an important factor in the instability of the landslide body, necessary drainage pipes can be arranged in the adit system to connect to the outside world. Draining water through drainage pipes is not only beneficial to the safety and stability of the adit, but also conducive to improving the stability of the entire landslide body.

[0012] Based on the landslide prevention and control construction monomer of the present invention, the present invention also provides a landslide prevention and control construction system, and its technical solution is as follows:

[0013] A landslide prevention and control construction system, characterized in that: it comprises a plurality of the above-mentioned landslide prevention and control construction units, and the vertical distance h2 between the upper and lower adjacent landslide prevention and control construction units is The H is the length of the micro steel pipe pile group.

[0014] The present invention also provides a design method for a landslide prevention and control structure unit, and its technical solution is as follows:

[0015] A design method for a landslide prevention and control structure unit is characterized by being implemented according to the following steps:

[0016] Step S1: Determine basic data

[0017] Field survey of the landslide body determines the thickness of the landslide body A, the depth of the sliding surface B, and the friction angle within the landslide body The average weight of the landslide body γ, the height of the landslide body before the pile H1,

[0018] According to the field survey data of the landslide body, determine the minimum height H for the construction equipment to enter the adit min , determine the outer diameter d of the geological pipe,

[0019] According to the Code for Design and Construction of Landslide Prevention Engineering (DZT0219-2006), the length H of the micro steel pipe pile group, the spacing a1 of the micro steel pipe pile group in the direction of the entrance tunnel, the spacing b1 of the micro steel pipe pile group in the direction of the wing tunnel, the number m of the rear group of steel pipe piles embedded in the concrete-cast cubic pile, and the number n of the front group of steel pipe piles embedded in the concrete-cast cubic pile are determined.

[0020] According to the Technical Specifications for Building Pile Foundations (JGJ94-2008), the mutual influence coefficient η between piles is determined. i , Pile top constraint effect coefficient η r , horizontal resistance effect coefficient of lateral soil of capping platform η l , Friction effect coefficient of the foundation bottom η b , characteristic value of horizontal bearing capacity of steel pipe pile R ha , the thickness of the concrete protective layer of the concrete poured cubic pile c,

[0021] The structural coefficient ζ of the micro steel pipe pile group connecting beam is determined by experimental measurement of the physical structure model scaled according to the similarity principle;

[0022] Step S2: Determine the entrance tunnel parameters

[0023] The height of the entrance tunnel opening from the ground is H min , determine the internal space structure parameters of the entrance adit according to the landslide body shape and the sliding surface depth B;

[0024] Step S3: Determine the parameters of the micro steel pipe pile group

[0025] Step S31: Calculate and determine a and b

[0026]

[0027] S1=(md+id+c)*b Formula 2

[0028] a=1.5b Formula 3

[0029] S=ab Formula 4

[0030] Where, S is the cross-sectional area of ​​micro steel pipe piles, in m 2 ,

[0031] S1—cross-sectional area of ​​the bending resistance zone of micro steel pipe pile group, unit: m 2 ,

[0032] m—number of rows of steel pipe piles in the rear group embedded in the concrete-cast cubic pile, determined in step S1,

[0033] d—geological pipe outer diameter, in mm, determined in step S1,

[0034] i—calculation coefficient, ranging from 1.5 to 2.0,

[0035] c—concrete cover thickness, in mm, determined in step S1,

[0036] a—The length of the micro steel pipe pile group in the direction of the entrance tunnel, in m.

[0037] b—the length of the micro steel pipe pile group in the direction of the flank tunnel, in m;

[0038] Step S32: Calculate and determine h1, h, x

[0039] According to Formula 5, the embedding depth h1 of the micro steel pipe pile group extending downward into the slope below the sliding surface is determined:

[0040] h1=λH Formula 5

[0041] Where, h1 is the embedding depth of the steel pipe pile group into the slope below the sliding surface, in m.

[0042] λ—embedded depth coefficient, value

[0043] Calculate the height h of the concrete poured cubic pile according to formula 6:

[0044] h=μH Formula 6

[0045] Where, h is the height of the concrete poured cubic pile, in m.

[0046] μ—concrete pile proportion coefficient. If the thickness of the landslide body A is less than 50m, μ is 0.2; if the thickness of the landslide body A is greater than 100m, μ is 0.5; if the thickness of the landslide body A is between 50m and 100m, μ is between 0.2 and 0.5 according to a linear growth relationship;

[0047] Determine the transverse center spacing x of each row of steel pipe piles embedded in the concrete poured cubic piles = 3d to 6d, where d is the outer diameter of the geological pipe, as determined in step S1;

[0048] Step S33: Calculate and determine k

[0049] The width W of the flank tunnel is calculated and determined according to formula 7, formula 8, formula 9 and formula 10:

[0050]

[0051] R h =(1+ζ)(η i η r +η l +η b )R ha Formula 8

[0052]

[0053]

[0054] Where, W is the width of the micro steel pipe pile group in the side tunnel near the slope, in m.

[0055] F—horizontal force per meter of the landslide body, unit KN / m,

[0056] R h — Characteristic value of horizontal bearing capacity of micro steel pipe pile group, unit Kp a ,

[0057] η i —Inter-pile interaction coefficient, determined in step S1,

[0058] η r —Pile top constraint effect coefficient, determined in step S1,

[0059] ηl —Horizontal resistance effect coefficient of lateral soil of the cap, determined in step S1,

[0060] η b — Friction effect coefficient of the bottom of the cap, determined in step S1,

[0061] ζ—micro steel pipe pile group connecting beam structure coefficient, determined in step S1,

[0062] R ha — Characteristic value of horizontal bearing capacity of steel pipe pile, unit Kp a , step S1 determines,

[0063] γ—average weight of landslide mass, unit KN / m 3 , step S1 determines,

[0064] H1—height of the landslide body in front of the pile, in meters, determined in step S1.

[0065] K a —active earth pressure coefficient,

[0066] —friction angle of the landslide body, in degrees, determined in step S1;

[0067] The number k of micro steel pipe piles arranged near the slope in the flank adit is determined by formula 11:

[0068]

[0069] Where, k is the number of micro steel pipe piles arranged close to the slope in the side tunnel.

[0070] b—the length of the micro steel pipe pile group in the flank direction, in meters, determined in step S2.

[0071] b1—the spacing of the micro steel pipe pile groups in the flank direction, in m, determined in step S1;

[0072] Step S4: Determine the side tunnel parameters

[0073] The length L of the wing tunnel is calculated according to formula 12, and the width D of the wing tunnel is calculated according to formula 13. The height of the wing tunnel is the same as the height of the entrance tunnel:

[0074] L=W+l Formula 12

[0075] D=2a+a1+l Formula 13

[0076] Where, l is the construction operation space, in m, determined based on the project site conditions.

[0077] The present invention also provides a construction method for a landslide prevention and control structure unit, and its technical scheme is as follows:

[0078] A construction method for a landslide prevention and control structure unit, characterized in that:

[0079] First, determine the opening coordinates of the entrance tunnel and excavate the tunnel into the landslide body according to the operating specifications;

[0080] Secondly, when the excavation of the entrance tunnel reaches the designed length / depth, side tunnels are excavated to the left and right sides, and the side tunnels are symmetrical along the axis of the entrance tunnel.

[0081] Next, cast the first row of micro steel pipe piles and install the steel truss on the side of the wing adit, and if necessary, move b1 to the slope side to cast the second row of micro steel pipe piles and install the steel truss.

[0082] Finally, deformation monitoring equipment is installed on the micro steel pipe pile group, and drainage pipes are installed inside the entrance tunnel and / or the side tunnel.

[0083] Compared with the prior art, the beneficial effects of the present invention are: (1) the single-unit adit system (including the entrance adit and the side adit) of the landslide prevention and control structure is located in an easily accessible and relatively stable area, which facilitates the transportation of materials and the entry and exit of workers, reduces the risk of landslides caused by excavating too deep pile holes, and increases safety and convenience; the existence of the adit makes it possible to install monitoring equipment and drainage equipment, reduces the factors that cause the instability of the landslide body, and is also conducive to maintenance. (2) Micro steel pipe piles only need to be buried near the sliding surface, which greatly reduces the depth of the piles, the probability of encountering boulders and the difficulty of drilling, and saves construction costs; the new method of embedding micro steel pipe piles inside the tunnel can effectively shorten the length of the piles, so that the high-steep and thick landslides that were originally not suitable for the pile method can choose the pile anchoring method; the micro steel pipe piles buried in the landslide body and the stratum under the sliding surface allow the landslide body to undergo slight deformation, which is conducive to the stability of the connection between the landslide body and the micro steel pipe pile group system; the two rows of steel pipe piles arranged in the tunnel are connected by a truss structure, which greatly improves the shear resistance and anti-slip ability of the anti-slide piles; compared with ordinary anti-slide pile structures, the concrete cast cubic piles of the micro steel pipe piles are shorter in length and the diameter of the steel pipe piles followed by drilling is smaller, which significantly reduces the disturbance to the soil layer around the landslide body. (3) The landslide prevention and control structure can be expanded into a multi-layer system according to the terrain needs, which is easy to design a landslide prevention and control plan for the entire landslide body. (4) Provides the design and construction methods of landslide prevention and control structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 It is a schematic diagram of the side section structure of the landslide body and the landslide prevention and control structure.

[0085] Figure 2 It is a schematic diagram of the top section structure of the landslide body and the landslide prevention and control structure.

[0086] Figure 3 It is a schematic plan view of the plane structure of a group of micro steel pipes (a group of steel pipe piles are shown by the dotted line box).

[0087] Figure 4 It is a schematic cross-sectional view of the steel pipe pile.

[0088] Figure 5 It is a schematic structural view of the landslide prevention and control construction system.

[0089] The numerical markings in the attached drawings are respectively:

[0090] 1 Entrance adit 11 Entrance of the entrance adit 12 End of the entrance adit 2 Flank adit 3 Group of micro steel pipes 31 Concrete-cast cubic pile 32 Steel pipe pile 321 Geological pipe 322 Steel bar 4 Steel bar truss 5 Slope surface 6 Slip surface Specific implementation manners

[0091] The preferred embodiments of the present invention will be further described below with reference to the attached drawings.

[0092] Embodiment 1

[0093] Construct the landslide prevention and control construction monomer of the present invention on a certain landslide body.

[0094] A certain landslide body is located in the high-intensity seismic area of Sichuan-Tibet. Through on-site survey of the landslide body, it is determined that the landslide accumulation layer mainly consists of a small amount of yellowish-brown and grayish-brown silty clay with broken stones in the surface layer and gravel in the lower part. The bedrock is metamorphic sandstone, which is suitable for the landslide prevention and control construction monomer of the present invention. The slope is 35°, the thickness A of the landslide body is 50 m, and the depth B of the slip surface is 50 m. It belongs to a high-steep and thick landslide body.

[0095] Figure 1 It is a schematic side-sectional view of the landslide body and the landslide prevention and control construction monomer, Figure 2 It is a schematic top-sectional view of the landslide body and the landslide prevention and control construction monomer. The landslide prevention and control construction monomer is arranged within the first 1 / 3 range in front of the landslide body; it includes an entrance adit 1 and a flank adit 2 that are perpendicular to each other to form a T-shaped plane; the entrance of the entrance adit 1 is on the slope surface and horizontally extends into the landslide body to the slip surface; the end 12 of the entrance adit is connected to the flank adit 2, and a group of micro steel pipes 3 are arranged in the flank adit 2; the group of micro steel pipes 3 extends upward into the landslide body and downward into the slope body below the slip surface. The group of micro steel pipes 3 is arranged in two rows in a triangular pattern. The first row of the group of micro steel pipes 3 is closer to the landslide body, and the second row of the group of micro steel pipes 3 is closer to the slope surface and the number of the micro steel pipes 3 at both ends is reduced by one group compared with the first row; there is a steel bar truss 4 between the groups of micro steel pipes 3.

[0096] Figure 3The micro steel pipe pile group 3 has two groups of steel pipe piles 32 embedded in the concrete-cast cubic piles 31, the rear group of steel pipe piles 32 is close to the slope, and the front group of steel pipe piles 32 is close to the slope surface.

[0097] Figure 4 The steel pipe pile 32 comprises an outer geological pipe 321, the lower part of the geological pipe 321 is processed into a flower pipe, the center of the geological pipe 321 is a steel bar 322 bundled in a shape of a triangle, and mortar is poured between the geological pipe 321 and the steel bar 322.

[0098] The design method of the landslide prevention and control structure is as follows:

[0099] Step S1: Determine basic data

[0100] Field survey to determine the friction angle of landslide body The average weight of the landslide is γ = 26.5 kN / m 3 , the height of the landslide body in front of the pile is H1=50m.

[0101] According to the field survey data of the landslide body, determine the minimum height H for the construction equipment to enter the adit min =60m, which is the height of the landslide prevention and control structure unit from the ground, and determines the outer diameter of the geological pipe 321 d=146mm.

[0102] According to the Code for Design and Construction of Landslide Prevention and Control Projects (DZT0219-2006), the length of the micro steel pipe pile group 3 is H=35m, the spacing of the micro steel pipe pile group 3 in the direction of the entrance tunnel 1 (x-axis direction) is a1=4m, the spacing of the micro steel pipe pile group 3 in the direction of the side tunnel 2 (y-axis direction) is b1=6m, the number of rows of the rear group of steel pipe piles 32 implanted in the concrete-cast cubic piles 31 is m=2, and the number of rows of the front group of steel pipe piles 32 implanted in the concrete-cast cubic piles 31 is n=1.

[0103] According to the Technical Specifications for Building Pile Foundations (JGJ94-2008), the mutual influence coefficient η between piles is determined. i =0.84, Pile top constraint effect coefficient η r =2.2, horizontal resistance effect coefficient of lateral soil of capping platform η l =0.015, friction effect coefficient of the bottom of the cap η b =0.008, characteristic value of horizontal bearing capacity of steel pipe pile R ha =37.5Kpa, concrete cast cubic pile 31 concrete protection layer thickness c = 70mm.

[0104] The structural coefficient of the micro steel pipe pile group connecting beam ζ=0.5 was determined by experimental measurement of the physical structure model scaled by similarity principle.

[0105] Step S2: Determine the entrance tunnel parameters

[0106] The height of the entrance tunnel opening 11 from the ground is H min According to the shape of the landslide body and the depth B of the sliding surface, the coordinate position of the entrance of the entrance tunnel is determined to be in the middle of the landslide body. The internal spatial structure parameters of the entrance tunnel include length / depth 71.4m, space height 3m, and left and right width 2m.

[0107] Step S3: Determine the parameters of the micro steel pipe pile group

[0108] Step S31: Calculate and determine a and b

[0109] Substitute m = 2, d = 146, i = 1.5d (the specific value is selected in consideration of reducing the cross-sectional area of ​​a single pile and making the bending resistance as high as possible), c = 70mm into formula 1, formula 2, formula 3, and formula 4, and we can calculate S1 = 1.2m 2 , a=3m, b=2m.

[0110] Step S32: Calculate and determine h1, h, x

[0111] Will (The specific value takes into account that the bedrock is metamorphic sandstone, and the deposit is mainly fragmented stone and soil, and the connectivity between the deposit and the bedrock needs to be improved), H is substituted into formula 5, and h1=14m, μ=0.2, H is substituted into formula 6, and h=7m, and the lateral center spacing x of each row of steel pipe piles 32 is determined to be 3d=438mm (the specific value takes into account reducing the cross-sectional area of ​​the piles and improving the strength of the single pile body).

[0112] Step S33: Calculate and determine k

[0113] Set ζ、η i , η i , η r , η b , R ha Substituting into formula 8, we have R h =105.24Kpa, Substituting δ, γ, and H1 into equations 9 and 10 yields K a =0.17, F = 5631KN / m, F, R h Substituting into formula 7, we have W = 56m.

[0114] Substituting b, b1, and W into equation 11, we have k=7.

[0115] Step S4: Determine the side tunnel parameters

[0116] According to the conditions of the project site, the construction operation space l = 2m is determined. The length of the wing tunnel L (x-axis direction) = 56m is calculated according to formula 12, and the width of the wing tunnel D (y-axis direction) = 12m is calculated according to formula 13. The height of the wing tunnel is the same as the height of the entrance tunnel, which is 3m.

[0117] Embodiment 2

[0118] Construction of landslide prevention and control structure units.

[0119] First, determine the coordinates of the entrance tunnel opening 11, and excavate the tunnel into the landslide body according to the operation specifications (construction along the x-axis direction);

[0120] Secondly, when the excavation entrance tunnel reaches the designed length / depth, side tunnels are excavated to the left and right sides (constructed along the y-axis direction), and the side tunnels are symmetrical along the axis of the entrance tunnel.

[0121] Next, cast the first row of micro steel pipe piles and install the steel truss on the side of the wing adit, and if necessary, move b1 to the slope side to cast the second row of micro steel pipe piles and install the steel truss.

[0122] Finally, deformation monitoring equipment (including displacement, crack, and tilt monitoring equipment directly installed on the micro-steel pipe pile group body) is installed on the micro-steel pipe pile group, and drainage pipes are installed inside the entrance tunnel and / or the side tunnel.

[0123] Embodiment 3

[0124] A landslide prevention and control structure unit is added on the basis of the first embodiment to form a landslide prevention and control structure system.

[0125] Figure 5 The landslide prevention and control system includes a plurality of landslide prevention and control structures in the first embodiment, each of which is arranged in a high and low position along the sliding direction of the landslide body, and the vertical distance h2 between the upper and lower adjacent landslide prevention and control structures is H is the length of the micro steel pipe pile group 3. The specific value of h1 can be Therefore, in the first embodiment, the value of h1 is Then the value of h2 in this system is

Claims

1. A single-body design method for landslide prevention and control structures, characterized in that: The landslide prevention and control structure is arranged within the front 1 / 3 of the landslide body, and includes an entrance tunnel (1) and a wing tunnel (2) which are perpendicular to each other and form a T-shaped plane; the entrance tunnel (1) opens on the slope surface and extends horizontally into the slope body to the sliding surface; the end (12) of the entrance tunnel is connected to the wing tunnel (2), and a micro steel pipe pile group (3) is arranged in the wing tunnel (2); the micro steel pipe pile group (3) extends upward into the landslide body and downward into the slope below the sliding surface, and the micro steel pipe pile group ( 3) two groups of front and rear steel pipe piles (32) are implanted in the concrete poured cubic piles (31), the rear group of steel pipe piles (32) is close to the slope, and the front group of steel pipe piles (32) is close to the slope surface; the steel pipe piles (32) include an outer geological pipe (321), the lower part of the geological pipe (321) is processed into a flower pipe, the center of the geological pipe (321) is a steel bar (322) bundled in a triangular shape, and mortar is poured between the geological pipe (321) and the steel bar (322); the landslide prevention and control structure monomer is implemented according to the following steps: Step S1: Determine basic data Field survey of the landslide body determines the thickness of the landslide body A, the depth of the sliding surface B, and the friction angle within the landslide body φ , average weight of landslide γ , Height of landslide in front of pile H 1, According to the field survey data of the landslide, determine the minimum height for the construction equipment to enter the adit H min , determine the outer diameter d of the geological pipe (321), According to the "Design and Construction Specifications for Landslide Prevention Engineering DZT0219-2006", the length of the micro steel pipe pile group (3) is determined H , the spacing a1 of the micro steel pipe pile group (3) in the direction of the entrance tunnel (1), the spacing b1 of the micro steel pipe pile group (3) in the direction of the wing tunnel (2), the number m of rows of the rear group steel pipe piles (32) implanted in the concrete cast cubic piles (31), the number n of rows of the front group steel pipe piles (32) implanted in the concrete cast cubic piles (31), Determine the mutual influence coefficient between piles according to the Technical Specifications for Building Pile Foundations (JGJ94-2008) η i , Pile top constraint effect coefficient η r , Horizontal resistance effect coefficient of lateral soil of cap η 1. Friction effect coefficient of the bottom of the cap η b , Characteristic value of horizontal bearing capacity of steel pipe pile R ha , concrete cast cubic pile (31) concrete cover thickness c, Determination of micro steel pipe pile group connection beam structural coefficients by experimental measurement of physical structure model scaled according to similarity principle ζ ; Step S2: Determine the entrance tunnel parameters Height of entrance tunnel opening (11) from ground level H min , determine the internal space structure parameters of the entrance adit according to the landslide body shape and the sliding surface depth B; Step S3: Determine the parameters of the micro steel pipe pile group Step S31: Calculate and determine a and b Formula 1 Formula 2 Formula 3 Formula 4 In the formula, S —Cross-sectional area of ​​micro steel pipe piles, unit: m 2 , S 1—Cross-sectional area of ​​the bending resistance zone of the micro steel pipe pile group, unit: m 2 , m—the number of rows of the rear group of steel pipe piles (32) implanted in the concrete-cast cubic pile (31), determined in step S1, d—outer diameter of the geological pipe (321), in mm, determined in step S1, i—calculation coefficient, ranging from 1.5 to 2.0, c—concrete cover thickness, in mm, determined in step S1, a—length of the micro steel pipe pile group (3) in the direction of the entrance tunnel (1), in meters, b—the length of the micro steel pipe pile group (3) in the direction of the flank tunnel (2), in meters; Step S32: Calculate and determine h1, h, x The embedding depth h1 of the micro steel pipe pile group (3) extending downward into the slope below the sliding surface is determined by calculation according to Formula 5: Formula 5 Where, h1 is the embedding depth of the steel pipe pile group into the slope below the sliding surface, in m. λ —Embedment depth coefficient, ranging from 1 / 3 to 1 / 2; Calculate the height h of the concrete poured cubic pile (31) according to formula 6: Formula 6 Where, h is the height of the concrete cast cubic pile (31), in meters. μ —Concrete pile proportional coefficient, if the thickness of the landslide body A is less than 50m μ Take the value as 0.

2. If the thickness of the landslide body A is greater than 100m, μ Take the value as 0.

5. If the thickness of the landslide body A is between 50m and 100m, μ The value is taken between 0.2 and 0.5 according to the linear growth relationship; Determine the transverse center spacing x of each row of steel pipe piles (32) implanted in the concrete cast cubic piles (31) = 3d to 6d, where d is the outer diameter of the geological pipe (321), step S1 determines; Step S33: Calculate and determine k The width W of the wing tunnel (2) is calculated and determined according to Formula 7, Formula 8, Formula 9 and Formula 10: Formula 7 Formula 8 Formula 9 Formula 10 Where W is the layout width of the micro steel pipe pile group (3) near the slope side in the side tunnel (2), in meters. F—horizontal force per meter of the landslide body, unit KN / m, R h — Characteristic value of horizontal bearing capacity of micro steel pipe pile group, unit Kp a , η i — Mutual influence coefficient between piles, determined in step S1, η r —Pile top constraint effect coefficient, determined in step S1, η 1—Horizontal resistance effect coefficient of lateral soil of the cap, determined in step S1, η b — Friction effect coefficient of the bottom of the cap, determined in step S1, ζ —Micro steel pipe pile group connection beam structure coefficient, determined in step S1, R ha — Characteristic value of horizontal bearing capacity of steel pipe pile, unit Kp a , step S1 determines, γ —Average weight of landslide mass, unit: KN / m 3 , step S1 determines, H 1 — Height of the landslide body in front of the pile, in meters, determined in step S1, K a —active earth pressure coefficient, φ —friction angle of the landslide body, in degrees, determined in step S1; The number k of the micro steel pipe pile group (3) arranged near the slope in the side tunnel (2) is determined by calculation according to formula (11): Formula 11 Where k is the number of micro steel pipe piles (3) arranged close to the slope in the side tunnel (2). b—the length of the micro steel pipe pile group (3) in the direction of the flank tunnel (2), in meters, determined in step S2, b1—the distance between the micro steel pipe pile group (3) in the direction of the flank tunnel (2), in m, determined in step S1; Step S4: Determine the side tunnel parameters Determine the length of the side tunnel according to formula 12 L , the side tunnel width D is determined by formula 13, and the side tunnel height is the same as the entrance tunnel height: Formula 12 Formula 13 In the formula, l —Construction operation space, unit: m, determined based on construction site conditions.

2. The method for designing a single unit of a landslide prevention and control structure according to claim 1, characterized in that: The micro steel pipe pile groups (3) are arranged in two rows in a triangular shape; and steel bar trusses (4) are provided between the micro steel pipe pile groups (3).

3. The method for designing a single unit of a landslide prevention and control structure according to claim 1, characterized in that: The embedding depth h1 of the steel pipe pile group extending into the slope below the sliding surface is 1 / 2 to 1 / 3 of the length H of the micro steel pipe pile group (3).

4. The method for designing a single unit of a landslide prevention and control structure according to claim 1, characterized in that: The landslide body is a high and steep slope with a landslide body thickness of not less than 50 m.

5. The method for designing a single unit of a landslide prevention and control structure according to claim 1, characterized in that: Drainage pipes are arranged in the entrance tunnel (1) and / or the side tunnel (2) to communicate with the outside.

6. The method for designing a single unit of a landslide prevention and control structure according to claim 1, characterized in that: The landslide prevention and control structural units are arranged in a high and low order along the sliding direction of the landslide body, and the vertical distance h2 between the upper and lower adjacent landslide prevention and control structural units is 1 / 2H to 2 / 3H, where H is the length of the micro steel pipe pile group (3).

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