Integrated loess landslide reinforcement and drainage method

Abstract

The invention discloses an integrated loess landslide reinforcement and drainage method, which belongs to the technical field of loess landslide reinforcement and drainage methods, utilizes the functions of an anchor rod and drainage of a self-starting siphon drainage device, combines self anchoring of a high and steep loess slope with a drainage structure, drains the slope, reduces the underground water level line of the slope, and improves the drainage effect of the loess landslide. The purpose of slope treatment is achieved, drainage and reinforcement are integrated, and the stability of the slope is guaranteed; the drainage-reinforcement device is made of a novel material which is different from a traditional metal material, a PVC base material is also suitable for a high-corrosion soil body, meanwhile, the technological processes such as grouting are reduced, the construction cost is reduced, high efficiency and convenience are achieved, in addition, the self weight of a device body is reduced, the integrity is high, and the effectiveness and stability of treatment are improved; a traditional drainage-reinforcement device mainly depends on the fact that water flows into a drainage channel, but when the permeability of a soil body is low, the drainage effect is seriously reduced.

Description

Technical Field

[0001] The invention relates to a loess landslide reinforcement and drainage method, in particular to an integrated loess landslide reinforcement and drainage method, and belongs to the technical field of loess landslide reinforcement and drainage methods. Background Art

[0002] Loess soil has unique engineering properties and is prone to strength degradation when exposed to water. Loess slopes within human activity areas often develop into high-angle slopes due to human engineering damage. Furthermore, rising groundwater levels due to rainfall or irrigation can ultimately lead to slope instability. Therefore, it is necessary to effectively lower the groundwater level and reinforce the slope. Common slope management methods currently include gravity retaining structures, anchor support, curtain grouting, and drainage systems. However, most of these methods suffer from the following problems:

[0003] The drainage and reinforcement functions are separated, the construction process is complicated, and the construction period is long;

[0004] Traditional drainage systems mostly use metal pipes, which are susceptible to corrosion and have a short service life;

[0005] The lack of real-time response capabilities to groundwater dynamics results in unsatisfactory early landslide prevention and control efforts;

[0006] The drainage efficiency is low and it is difficult to meet the demand for large amounts of seepage water discharge under sudden heavy rainfall conditions.

[0007] Therefore, an integrated loess landslide reinforcement and drainage method is designed to solve the above problems. Summary of the Invention

[0008] The main purpose of the present invention is to provide an integrated loess landslide reinforcement and drainage method.

[0009] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0010] An integrated loess landslide reinforcement and drainage method comprises the following steps:

[0011] Step 1: Using geophysical exploration methods, determine the natural groundwater level on the steep loess slopes and the changes in water level caused by human activities;

[0012] Step 2: Establish a dynamic relationship model between soil permeability coefficient and drainage hole spacing to determine the optimal drainage hole layout;

[0013] Step 3: Set up a self-starting siphon drainage system with coupled drainage and anchoring effects;

[0014] Step 4: Based on the geological parameters and hydrological conditions of the slope, calculate the thickness of the potential sliding surface and determine the drilling depth range;

[0015] Step 5: According to the changes in groundwater levels in different areas, dynamically adjust the drainage device layout angle, frame length and sealing plug position to establish a drainage structure.

[0016] Preferably, the self-starting siphon drainage system in step 2 includes a filter-water collection component, which is composed of a non-perforated PVC tubular frame, a perforated PVC tubular frame and a geotextile;

[0017] The frame is provided with openings;

[0018] The drainage assembly includes a siphon drain pipe 4 and an adjustable sealing plug provided in the non-perforated PVC tubular frame and the perforated PVC tubular frame;

[0019] and a water collection tank at the foot of the slope connected to the non-perforated PVC tubular frame through a siphon drain pipe 4;

[0020] The anchoring assembly adopts an anchor rod structure made of the same material as the supporting frame. A sliding self-expanding anchor head is set at the bottom of the perforated section of the PVC tubular frame, and an anchor rod pad is set at the top of the non-perforated section of the PVC tubular frame.

[0021] Preferably, the slope parameter calculation includes:

[0022] Potential sliding surface identification algorithm based on Mohr-Coulomb criterion;

[0023] Seepage analysis is performed using the modified Darcy's law based on the nonlinear seepage characteristics of soil;

[0024] The impact of drainage system on seepage field is simulated and stability evaluated based on finite element method.

[0025] Preferably, in step 5, the layout parameters of the drainage device are dynamically adjusted as follows:

[0026] By monitoring the groundwater level distribution and combining it with the calculated potential sliding surface depth, the angle and depth of drainage boreholes at different locations on the slope are changed;

[0027] Based on the slope moisture gradient and numerical simulation results, a parameter optimization algorithm was used to adjust the sealing plug position to ensure the siphon start-up effect;

[0028] A three-dimensional model was created based on the slope topography. The model included the actual water level inside the slope and the layout of the drainage device. The numerical simulation results verified the coordinated working status of the drainage anchor system and the stability of the slope after construction, thereby optimizing the design solution.

[0029] Preferably, the filtration-water collection assembly is formed by wrapping a composite filtration layer consisting of an outer coarse filtration geotextile and an inner fine filtration membrane around the outside of a perforated PVC tubular skeleton;

[0030] The sliding self-expanding anchor head is provided with an annular tooth groove.

[0031] Beneficial technical effects of the present invention:

[0032] The present invention provides an integrated loess landslide reinforcement and drainage method, which utilizes the anchor rod and drainage functions of the self-starting siphon drainage device to combine the anchoring and drainage structure of the steep loess slope to drain the slope and lower the groundwater level of the slope, thereby achieving the purpose of slope management, integrated drainage and reinforcement, and ensuring the stability of the slope; the drainage-reinforcement device adopts new materials, which are different from traditional metal materials. The PVC substrate is also suitable for highly corrosive soils, while reducing grouting and other process processes, reducing construction costs and being efficient and convenient. In addition, the weight of the device body is reduced, the integrity is strong, and the effectiveness and stability of management are improved; the traditional drainage-reinforcement device mainly relies on water flowing into the drainage channel, but when the soil permeability is low, The drainage effect is seriously reduced, the drainage time is increased, and the risk of instability of high and steep loess slopes is seriously increased. The self-starting siphon drainage described in the present invention has a negative pressure effect, which will produce a suction effect, which can effectively increase the drainage flow rate and improve the drainage capacity of the device. At the same time, it has a certain compaction effect on the surrounding soil. Therefore, the device is also suitable for drainage and reinforcement of low-permeability soils. In terms of applicability, traditional slope anchoring force and stability calculations often use the limit equilibrium method. This method is simple in concept, but it is difficult to apply to the stability analysis of slopes after drainage-reinforcement projects. The finite element strength reduction method can take into account the slope stability analysis under various complex working conditions, but it is relatively profound and not suitable for ordinary front-line engineering personnel. Therefore, the present invention combines the oblique strip method with the numerical simulation method to provide a concise empirical formula for analyzing the stability of slopes after drainage-reinforcement and optimizing the design and layout of drainage-reinforcement devices.

[0033] During slope control construction, drainage anchor rods of different lengths and angles are arranged according to the depth and location of the potential sliding surface and the distribution of groundwater levels to achieve the optimal drainage effect under different working conditions. In addition, ordinary anchor rods can be appropriately added to utilize their strength to improve the overall reliability of the drainage-reinforcement system and enhance the effectiveness of the control project. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the overall layout of a drainage-reinforcement device according to a preferred embodiment of an integrated loess landslide reinforcement and drainage method of the present invention;

[0035] Figure 2 The figure is a schematic structural diagram of a drainage-reinforcement device according to a preferred embodiment of an integrated loess landslide reinforcement and drainage method of the present invention.

[0036] In the figure: 1-potential sliding surface of the slope, 2-anchor pad, 3-groundwater level of the slope, 4-siphon drainage pipe, 5-tilted drainage borehole, 6-slope foot collection tank, 7-sealing plug, 8-non-perforated PVC tubular frame, 9-perforated PVC tubular frame, 10-geotextile, 11-sliding self-expanding anchor head. DETAILED DESCRIPTION

[0037] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is further described in detail below with reference to embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0038] The steps include:

[0039] Step 1: Using geophysical exploration methods, determine the natural groundwater level on the steep loess slopes and the changes in water level caused by human activities;

[0040] Step 2: Establish a dynamic relationship model between soil permeability coefficient and drainage hole spacing to determine the optimal drainage hole layout;

[0041] Step 3: Set up a self-starting siphon drainage system with coupled drainage and anchoring effects;

[0042] Step 4: Based on the geological parameters and hydrological conditions of the slope, calculate the thickness of the potential sliding surface and determine the drilling depth range;

[0043] Step 5: According to the changes in groundwater levels in different areas, dynamically adjust the drainage device layout angle, frame length and sealing plug 7 position to establish a drainage structure.

[0044] In this embodiment, the self-starting siphon drainage system in step 2 includes a filter-water collection assembly, which is composed of a non-perforated PVC tubular frame 8, a perforated PVC tubular frame 9 and a geotextile 10;

[0045] The frame is provided with openings;

[0046] Drainage assembly, including a siphon drain pipe 4 and an adjustable sealing plug 7 disposed within a non-perforated PVC tubular frame 8 and a perforated PVC tubular frame 9;

[0047] and a water collection tank 6 at the foot of the slope connected to a non-perforated PVC tubular skeleton 8 through a siphon drain pipe 4;

[0048] The anchoring assembly adopts an anchor rod structure made of the same material as the supporting frame. A sliding self-expanding anchor head 11 is provided at the bottom of the punched section PVC tubular frame 9, and an anchor rod pad 2 is provided at the top of the non-punched section PVC tubular frame 8.

[0049] In this embodiment, the slope parameter calculation includes:

[0050] Potential sliding surface identification algorithm based on Mohr-Coulomb criterion;

[0051] Seepage analysis is performed using the modified Darcy's law based on the nonlinear seepage characteristics of soil;

[0052] The impact of drainage system on seepage field is simulated and stability evaluated based on finite element method.

[0053] In this embodiment, in step 5, the layout parameters of the drainage device are dynamically adjusted as follows:

[0054] By monitoring the groundwater level distribution and combining it with the calculated potential sliding surface depth, the angle and depth of drainage boreholes at different locations on the slope are changed;

[0055] Based on the slope moisture gradient and numerical simulation results, a parameter optimization algorithm is used to adjust the position of the sealing plug 7 to ensure the siphon start-up effect;

[0056] A three-dimensional model was created based on the slope topography. The model included the actual water level inside the slope and the layout of the drainage device. The numerical simulation results verified the coordinated working status of the drainage anchor system and the stability of the slope after construction, thereby optimizing the design solution.

[0057] In this embodiment, the filtration-water collection assembly is formed by wrapping a composite filtration layer consisting of an outer coarse filtration geotextile and an inner fine filtration membrane around the outside of a perforated PVC tubular skeleton 9;

[0058] The sliding self-expanding anchor head 11 is provided with an annular tooth groove.

[0059] Empirical model of drainage hole spacing L:

[0060] When there is a lack of measured data, the drainage pipe influence radius R is generally calculated according to formula (1) in engineering.

[0061]

[0062] Where: R is the impact radius (m); s is the water level drawdown (m); K is the permeability coefficient (m / s); H is the aquifer thickness (m).

[0063] At this time, the drainage hole spacing L (m) can be temporarily set as:

[0064] L=2R(2)

[0065] Siphon start restrictions:

[0066] Previous studies have shown that the maximum lift of siphon in the Loess Plateau is about 8.4m.

[0067] Z·sinθ≤8.4(m)(3)

[0068] Where Z is the length of the drainage borehole and θ is the horizontal inclination angle of the drainage borehole.

[0069] General requirements:

[0070] According to the principles of anchor bolt layout in engineering construction, the overall layout of anchor bolts needs to produce the best anti-slip effect on the slope sliding body, and generally should meet the following basic requirements:

[0071] (1) The spacing and length of anchor rods should be determined based on the overall stability of the ground surrounding the anchoring project.

[0072] (2) In addition to meeting the anchor rod stress requirements, the anchor rod spacing must also be greater than 1.5 m to avoid a reduction in anchoring force due to the group anchor effect. The group anchor effect refers to the fact that rock and soil anchor rods usually appear in groups. If the anchor rods are arranged densely, the overlap of the stress-bearing areas in the stratum will cause stress superposition and anchor rod displacement, thereby preventing the anchor rod's ultimate pull-out resistance from being effectively exerted. The ultimate pull-out force of the anchor rod will be reduced by the group anchor effect, which is related to factors such as the anchor rod spacing, diameter, length, and stratum shape.

[0073] The spacing of the drainage-anchoring integrated anchor rods of the present invention is also affected by the groundwater level 3 of the slope. If the spacing used is less than 1.5m, the inclination angles of adjacent anchor rods should be adjusted to a difference of at least 3°.

[0074] (3) The distance between the anchor rod and the adjacent foundation or underground facilities should be greater than 3.0m.

[0075] (4) The anchor bolt anchoring section should be within the stable soil outside the potential sliding surface, and the thickness of the overlying soil layer should not be less than 4.5m to avoid the influence of repeated loads on the slope top. The drainage-anchoring integrated anchor bolt anchoring section described in the present invention mainly refers to the conical anchor head.

[0076] (5) For nearly vertical slopes, the angle of anchor rod placement must take into account the surrounding conditions, the location of the anchoring stratum, and the construction method. Generally, the inclination angle of anchor rods should be no less than 13° and no greater than 45°. The greater the inclination angle, the weaker the anti-slip ability will be. Therefore, the appropriate anchor rod placement angle is 15-35°.

[0077] For slopes damaged by sliding, the layout angle of the anchor rod should give full play to the anti-slip effect of the anchor rod. Under feasible construction conditions, the anchor rod inclination angle can generally be calculated as follows:

[0078]

[0079] Among them, θ is the anchor rod inclination angle (i.e. the horizontal inclination angle of the drainage borehole mentioned above), β is the slope gradient, is the internal friction angle of soil.

[0080] (6) In general, the appropriate length of the anchor section in loess is 6-12 m. The length of the free section of the anchor should be determined based on the distance between the anchor and the potential sliding surface and the slope surface, and should generally not be less than 5.0 m. In addition, the free section should penetrate the potential sliding surface for at least 1.5 m to ensure the overall stability of the anchor system.

[0081] Based on the above formulas and explanations, parameters such as the number of drilling rows, spacing, angle, and depth can be preliminarily selected. Combined with the drainage device material and soil properties, and using limit equilibrium and numerical simulation methods, the overall stability of the drainage-anchor device and slope after construction can be verified, thereby optimizing the overall design in a timely manner.

[0082] The self-starting siphon drainage device mainly consists of the following three parts:

[0083] Filtration-water collection component: A PVC tubular skeleton with an open-pore structure is used, which is wrapped with a high-strength geotextile 10 to form an effective water filtration and collection device with pressure resistance, anti-clogging and corrosion resistance. The geotextile 10 is mainly made of a polymer protective drainage sheet composited with HDPE (high-density polyethylene) and PP (polypropylene), with high tensile strength, generally ≥15Mpa, and its vertical permeability coefficient is generally 1×10-3cm / s.

[0084] Drainage assembly: It consists of a siphon drain pipe 4 inserted into the bottom of the hole, equipped with a sealing plug to increase the water head, and the top is connected to the water collection tank 6 at the foot of the slope along the slope to form a siphon path;

[0085] Anchoring assembly: A sliding self-expanding anchor head 11 is set at the bottom of the device, and an anchor pad 2 is set at the top. By connecting it with the supporting frame as a whole, an anchoring system is formed, which has both pull-out and shear resistance.

[0086]

Construction process

[0087] Obtain the structural parameters, permeability coefficient and groundwater change trend of the slope through monitoring, geological survey and indoor testing;

[0088] Using the above model and empirical statistics, the drainage hole spacing L, layout angle θ and drilling depth Z at different locations are determined;

[0089] Use drilling equipment to drill appropriate drainage holes;

[0090] Install a siphon drainage device so that the water head at the water collection end of the device is higher than the orifice section to meet the siphon start-up conditions;

[0091] After the drainage is started, the device automatically drains the seepage water, and at the same time the anchoring effect of the sliding anchor head enhances the overall stability of the slope;

[0092] Regularly check the system operation status and optimize the deployment plan based on data feedback.

[0093] The above is only a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and concepts of the present invention within the scope disclosed by the present invention, which fall within the scope of protection of the present invention.

Claims

1. An integrated loess landslide reinforcement and drainage method, characterized by: The steps include: Step 1: Using geophysical exploration methods, determine the natural groundwater level on the steep loess slopes and the changes in water level caused by human activities; Step 2: Establish a dynamic relationship model between soil permeability coefficient and drainage hole spacing to determine the optimal drainage hole layout; Step 3: Set up a self-starting siphon drainage system with coupled drainage and anchoring effects; Step 4: Based on the geological parameters and hydrological conditions of the slope, calculate the thickness of the potential sliding surface and determine the drilling depth range; Step 5: According to the changes in groundwater levels in different areas, dynamically adjust the drainage device layout angle, frame length and sealing plug (7) position to establish a drainage structure.

2. The integrated loess landslide reinforcement and drainage method according to claim 1, characterized in that: In step 2, the self-starting siphon drainage system includes a filter-water collection component, which is composed of a non-perforated PVC tubular frame (8), a perforated PVC tubular frame (9) and a geotextile (10); The frame is provided with openings; A drainage assembly includes a siphon drain pipe 4 and an adjustable sealing plug (7) disposed in a non-perforated PVC tubular frame (8) and a perforated PVC tubular frame (9); and a water collection tank (6) at the foot of the slope connected to a non-perforated PVC tubular frame (8) via a siphon drain pipe 4; The anchoring assembly adopts an anchor rod structure made of the same material as the supporting frame, a sliding self-expanding anchor head (11) is provided at the bottom of the punched section PVC tubular frame (9), and an anchor rod pad (2) is provided at the top of the non-punched section PVC tubular frame (8).

3. The integrated loess landslide reinforcement and drainage method according to claim 1, characterized in that: The slope parameter calculation includes: Potential sliding surface identification algorithm based on Mohr-Coulomb criterion; Seepage analysis is performed using the modified Darcy's law based on the nonlinear seepage characteristics of soil; The impact of drainage system on seepage field is simulated and stability evaluated based on finite element method.

4. The integrated loess landslide reinforcement and drainage method according to claim 1, characterized in that: In step 5, the layout parameters of the drainage device are dynamically adjusted as follows: By monitoring the groundwater level distribution and combining it with the calculated potential sliding surface depth, the angle and depth of drainage boreholes at different locations on the slope are changed; Based on the slope moisture gradient and numerical simulation results, the parameter optimization algorithm is used to adjust the position of the sealing plug (7) to ensure the siphon start-up effect; A three-dimensional model was created based on the slope topography. The model included the actual water level inside the slope and the layout of the drainage device. The numerical simulation results verified the coordinated working status of the drainage anchor system and the stability of the slope after construction, thereby optimizing the design solution.

5. The integrated loess landslide reinforcement and drainage method according to claim 2, characterized in that: The filtration-water collection component is formed by wrapping a composite filtration layer consisting of an outer coarse filtration geotextile and an inner fine filtration membrane on the outside of a perforated PVC tubular skeleton (9); The sliding self-expanding anchor head (11) is provided with an annular tooth groove.

Images