Multi-layer gradient capillary barrier and pre-stressed anchor cable synergetic slope protection system and construction method thereof

Abstract

The invention relates to the field of slope protection engineering, in particular to a multi-layer gradient capillary barrier and pre-stressed anchor cable collaborative slope protection system and a construction method thereof. The geotextile bag protection wall body is arranged on a side slope, the angle of elevation between the geotextile bag protection wall body and the horizontal plane is 4-6 degrees, the tamping position of the anchor cable is the outer side of the geotextile bag protection wall body, and the extension direction of the anchor cable is from outside to inside. The geotextile bag filling aggregate is from the in-situ slope soil body, so that the slope can be supported without adding any concrete; after the anti-corrosion casing pipe, the anti-rust mortar and the anchor cable are matched for protecting the slope together, durability, high strength and high ductility are achieved, and high-strength supporting of the side slope under the extreme condition is effectively achieved under the condition of low cost. A multi-layer gradient capillary barrier is designed, the water blocking effect is enhanced through gradient change of the aggregate particle size, and meanwhile prestress distribution of the anchor cable is matched.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of slope protection engineering, in particular to a multi-layer gradient capillary barrier and prestressed anchor cable collaborative slope protection system and its construction method. BACKGROUND

[0002] The capillary barrier system CBS (Capillary Barrier System) forms a non-saturated seepage resistance zone through the hierarchical coverage of multi-grade aggregates, achieving the engineering ecological goal of "controlling slope with soil". The CBS system is constructed based on the theory of unsaturated seepage. When rainfall infiltrates, a matric suction gradient is generated at the interface between the fine aggregate layer and the coarse aggregate layer due to the sudden change in the permeability coefficient, forming a natural impermeable barrier (the measured resistance efficiency reaches 92%), effectively controlling the evolution of the slope seepage field. The soil bag is a new material technology widely used in geotechnical engineering, made of high-strength synthetic fibers, with good tensile strength and durability. The principle of the soil bag is to fill soil and reinforce the connection to form a stable structure, which can improve the strength and stability of the soil, enhance the anti-sliding and anti-erosion capacity, and is convenient to construct, suitable for different terrain conditions. Especially in complex areas, it has advantages and also has ecological and environmental performance, which can combine with vegetation to promote ecological restoration, therefore, the soil bag is usually used as the optimal carrier for building the capillary barrier system.

[0003] Anchor cable reinforcement is a geotechnical reinforcement technology for slope stability. At present, in slope reinforcement engineering, according to the stress state of the anchoring body, prestressed anchor cables are mainly divided into two categories: one is pressure dispersion type anchor cable, and the other is tension type anchor cable. Figure 1 As shown in the formula, the tension type anchor cable structure is composed of three parts: anchor head, steel strand and anchoring segment. The anchor head is exposed, which can transfer the anchoring force to the supporting members such as pile wall and apply prestress to the anchor cable. One end of the anchor cable is connected to the anchor head, and the other end is embedded in the stable rock-soil layer. The elastic deformation of the anchor cable allows it to be pre-stressed. The anchoring segment is at the end of the anchor cable. This part transmits the anchoring force of the anchor cable to the stable stratum through the grouting body. The tension type anchor cable construction technology is relatively mature, and the stress is uniform and reasonable, the anchoring force is large, and it has obvious advantages, so it is widely used in slope protection engineering. In the tension type anchor cable system, the anchor head tension P is converted into the shaft force N of the rod body, N transmits the load to the grouting body through the sufficient bonding strength of the rod body and the consolidation body interface, and then transmits the load to the soil around the hole in the form of interface shear stress τ through the interface between the consolidation body and the soil. The initial tension load P is small, the load is transmitted and balanced in the above manner, and the entire anchor cable system from the medium to the interface can be considered to be basically in the elastic stage. According to the load-displacement mutual equality theorem, with the help of Kelvin elastic displacement solution, the analytical expressions of the interface shear stress and the shaft force are obtained:

[0004]

[0005] wherein: μ is the Poisson's ratio of the rock-soil mass; D is the diameter of the borehole; E is the elastic modulus of the rock-soil mass; Ea is the elastic modulus of the consolidated mass; z is the distance from the calculation point to the starting position of the anchoring segment as the only variable.

[0006] Taking dτ / dz = 0 for formula (1) and substituting into the original formula, the maximum shear stress position and the peak shear stress in the elastic stage can be obtained:

[0007]

[0008] It can be seen from formula (3) that, in the case where the anchor cable material parameters and the rock-soil mass parameters are determined, the peak shear stress position in the elastic stage is determined, and the peak shear stress size is independent of the anchoring segment length, is proportional to the tension load P, is inversely proportional to the anchor body diameter D 2 , and is proportional to .

[0009] In the prestressed anchor cable engineering test, 0.1-0.2P is generally taken for pre-tightening before tensioning to ensure that the engineering anchor cable rod body is completely flat and the parts are in close contact. For formula (2), it is assumed that the anchoring segment axial force decays to the position of 0.1P (N = 0.1P), and the corresponding anchoring segment length is the critical anchoring segment length Lc, that is, at this time

[0010]

[0011] At this time, the interface shear stress at 0.1P is:

[0012]

[0013] From formula (4) and the composition of parameter t, the critical anchoring segment length Lc is independent of the tension load P, is proportional to the anchoring segment diameter D, and is inversely proportional to . The larger the diameter of the anchoring body and the smaller the elastic modulus of the rock-soil mass, the longer the critical anchoring segment length Lc.

[0014] Although the traditional soil bag capillary barrier system (CBS) has excellent durability and water-stopping and flow guiding functions, its relatively rigid characteristics result in a supporting strength that is 1-2 orders of magnitude lower than that of the anchor cable system. Although the anchor cable support has the advantages of high strength and high ductility, it has significant environmental sensitivity: under the condition of rainfall infiltration, the anchoring system not only faces the risk of steel corrosion, but also will cause the problem of rapid drop of the friction coefficient due to the increase of the interface water content. SUMMARY

[0015] The present application aims at the technical defects of the traditional supporting system in steep slope engineering in high rainfall area, and proposes a slope protection system with multi-layer gradient capillary barrier and prestressed anchor cable and a construction method thereof. The capillary barrier blocking layer (CBS) filled with soil bags and the prestressed anchor cable are structurally coupled to form a composite supporting system with multi-level protection function. The capillary barrier blocking layer (CBS) includes soil bags filled with fine aggregate and soil bags filled with coarse aggregate.

[0016] In order to achieve the above-mentioned target, the technical scheme adopted by the present application is as follows:

[0017] A slope protection system with multi-layer gradient capillary barrier and prestressed anchor cable, comprising a soil bag protection wall arranged on the slope and an anchor cable arranged at an angle of 4-6° with the horizontal plane, the ramming position of the anchor cable being the outer side of the soil bag protection wall, and the extension direction of the anchor cable being from outside to inside.

[0018] The soil bag protection wall, backfill soil and undisturbed foundation are sequentially arranged; the anchor cable, the corrosion-resistant sleeve and the rust-proof mortar form a mechanical interlocking structure with the soil bag protection wall; the ramming position of the anchor cable is 4-6 cm above the center point of the outer surface of the outer soil bag (i.e. the first soil bag) of the soil bag protection wall which is connected with the organic soil layer; the assembly mode of the corrosion-resistant sleeve and the anchor cable composite anchoring body is: from the outer soil bag to the inside, first set the corrosion-resistant sleeve at the position to be passed through by the anchor cable, the corrosion-resistant sleeve is hot-welded with the soil bag, the anchor cable is rammed into the corrosion-resistant sleeve, then the rust-proof mortar is filled into the corrosion-resistant sleeve, the rust-proof mortar is mixed by C50 mortar and a small amount of nitrite (such as sodium nitrite), the addition amount of nitrite is 1%-2% of the mass of the mortar; the end of the anchor cable is connected with a screw end rod, the screw end rod is exposed outside the soil bag protection wall; the anchor cable uses fiber reinforced plastic (FRP) as the main body of the anchor cable; the corrosion-resistant sleeve is a PVC or HDPE pipe.

[0019] The screw end rod is firmly combined with the main body of the anchor cable, and cooperates with the anchor (such as nut, anchor plate) to realize the final anchoring of the anchor cable.

[0020] When installing the corrosion-resistant sleeve, a pre-opening is pre-opened on the outer soil fabric of the soil bag, the corrosion-resistant sleeve passes through the pre-opening, and the connection between the corrosion-resistant sleeve and the outer soil fabric of the soil bag is sealed and fixed by hot melting or adhesive; the outer soil fabric refers to the bag body; the upper end of the soil bag protection wall is provided with a covering water stop layer, and the first layer of soil bags of the soil bag protection wall from top to bottom are all soil bags filled with fine aggregate; the covering water stop layer covers the first layer of soil bags.

[0021] The earthwork bag protection wall is composed of a plurality of earthwork bag capillary barrier units, each of which is sequentially arranged by a first earthwork bag filled with fine aggregate, a second earthwork bag filled with coarse aggregate, a third earthwork bag filled with fine aggregate and a fourth earthwork bag filled with coarse aggregate, the fourth earthwork bag is larger than the first to third earthwork bags, and the first earthwork bag is connected with an organic soil layer; the fine aggregate or the coarse aggregate is an unsaturated soil body obtained by screening and compaction of the in-situ excavated soil body of the slope; the earthwork bag is connected with an earthwork grid; all the earthwork bags filled with fine aggregate form a drainage layer, and all the earthwork bags filled with coarse aggregate form a water-blocking layer; the fourth earthwork bag filled with coarse aggregate is adjacent to the backfill soil.

[0022] The fine aggregate has a particle size of 0.075-0.25 mm, and 0.5%-2% nano-silicon dioxide is added to the fine aggregate; the coarse aggregate has a particle size of 0.5-1 mm, and 10%-40% bentonite, 0.1%-2% organosilane (such as methyl triethoxysilane, octyl triethoxysilane, etc.) and 0.5%-2% nano-silicon dioxide are added to the coarse aggregate; the mass ratio of the nano-silicon dioxide to the fine aggregate is 0.5%-2%, the mass ratio of the bentonite to the coarse aggregate is 10%-40%, and the mass ratio of the organosilane to the coarse aggregate is 0.1%-2%.

[0023] The slope of the flow guide surface of the earthwork bag protection wall is 25-35°; and the earthwork bags of different earthwork bag capillary barrier units are arranged in a staggered manner.

[0024] The corrosion-resistant sleeve is inserted from the center point of the outer surface of the outer earthwork bag of a certain earthwork bag capillary barrier unit connected with the organic soil layer to a position 4-6 cm above the center point (referring to the center of the corrosion-resistant sleeve being inserted to a position 4-6 cm above the center point of the outer surface), and sequentially passes through the other three earthwork bags of the earthwork bag capillary barrier unit, and is then hot-welded with the earthwork bags; the anchor cable is inserted into the corrosion-resistant sleeve from the center of the corrosion-resistant sleeve, and the corrosion-resistant sand mortar is filled between the corrosion-resistant sleeve and the anchor cable, and the anchor cable is finally anchored in the backfill soil; the anchor cable and the corrosion-resistant sleeve are located in the four earthwork bags of a certain earthwork bag capillary barrier unit, and the end of the anchor cable is anchored in the backfill soil. The high-strength corrosion-resistant anchoring system composed of the corrosion-resistant sleeve, the anchor cable and the sand mortar is located in the four earthwork bags of the first earthwork bag layer of a certain earthwork bag capillary barrier unit, so as to fully fix the earthwork bag capillary barrier unit and maximize the service life of the anchor cable, the end of the anchoring section of the anchor cable is located in the backfill soil, and the anchoring strength and the stability of the anchor cable are improved.

[0025] Another object of the present application is to disclose a construction method of the aforementioned multi-layer gradient capillary barrier and prestressed anchor cable cooperative slope protection system, which comprises the following steps:

[0026] a. Hot-welding the anticorrosion sleeve with the geotextile bag, the diameter of the anticorrosion sleeve is 9-11 cm, the center of the anticorrosion sleeve is located 5 cm above the center point of the outer surface of the geotextile bag connected with the organic soil layer, and the anticorrosion sleeve forms an angle of 5° with the horizontal plane; the fine aggregate or coarse aggregate obtained by screening and compaction of the in-situ excavated soil of the slope is filled into the geotextile bag after being mixed with nano-silicon dioxide, bentonite and organosilane, and the bag is sealed;

[0027] b. Using the geogrid, a plurality of geotextile bags are connected through the geogrid to form a continuous geotextile bag protection wall;

[0028] c. Using the anchor cable, the anchor cable is rammed at the center of the anticorrosion sleeve, the anchor cable forms an angle of 5° with the horizontal plane, C50 rust-proof mortar mixed with nitrite is poured into the anticorrosion sleeve, and the end of the anchor cable is welded with a screw end rod; part of the screw end rod is exposed outside the geotextile bag;

[0029] d. The geotextile bag protection wall is placed at a position needing protection, and the position needing protection includes a river bank or a slope.

[0030] The anchor cable body is a fiber-reinforced plastic (FRP).

[0031] The construction steps of the anchor cable are as follows:

[0032] (1) Anchor cable positioning: the center of the anticorrosion sleeve is selected as the anchor cable ramming point;

[0033] (2) Anchor cable body determination: 15.6 mm high-strength fiber-reinforced plastic (FRP) arranged in a 1×7 structure is used as the anchor cable body;

[0034] (3) Angle control: the anchor cable forms an angle of 5° with the horizontal plane, so that the setting angle of the anchor cable is parallel to the anticorrosion sleeve;

[0035] (4) Assembly construction: the anchor cable and the geotextile bag form a mechanical interlocking structure through vibration ramming;

[0036] (5) Grouting body pouring: after the anchor cable is rammed, C50 mortar containing nitrite is poured into the anticorrosion sleeve;

[0037] (6) End treatment: a screw end rod is welded at the end of the anchor cable, the screw end rod is subjected to galvanizing anticorrosion treatment, and the length of the screw end rod exposed outside the geotextile bag is controlled within the range of 3-5 cm.

[0038] The pedestal, screw end rod and pressure plate of the anchor cable are exposed outside the geotextile bag; the outside of the geotextile bag protection wall is covered with organic soil. The pedestal abuts against the geotextile bag protection wall and helps to fix the anchor cable; the pressure plate is located between the pedestal and the anchor.

[0039] The present application has the following advantages:

[0040] The present application solves the problems of the traditional anchor cable slope protection system under the condition of rainfall penetration, such as the risk of steel corrosion, and the sudden drop of the friction coefficient caused by the increase of the interface moisture content, under the premise of safety, stability, greenness and environmental protection. The inventor found that the geotextile bag capillary barrier unit of the present application can effectively reduce the interface moisture content under the condition of penetration, thereby overcoming the above problems of the traditional anchor cable slope protection system. The corrosion-resistant sleeve and anchor cable composite anchoring body provide sufficient pullout friction resistance, so that the entire slope protection system has sufficient strength to cope with various adverse weather, and even some extreme conditions. In the case of geogrid stabilizing geotextile bag unit, the use of anchor cable further strengthens the integrity and stability of the geotextile bag system.

[0041] The geotextile bag in the system of the present application is integrally produced and assembled, and the filling aggregate comes from the in-situ slope soil, without adding any concrete to realize the support of the slope; after being matched with anchor cable for slope protection, due to the excellent tensile strength and ductility of the anchor cable, the in-situ soil does not need to bear the main support, the amount of excavated in-situ soil is greatly reduced, thereby the excavation cost is greatly reduced. At the same time, the slope protection system also has good environmental protection performance, and the application of in-situ soil eliminates the pollution that may be caused by concrete from the root. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic diagram of the structure of the corrosion-resistant sleeve and anchor cable composite anchoring body;

[0043] Figure 2 is a side sectional view of the slope protection system;

[0044] Meaning of reference signs in the drawing:

[0045] Wherein, 1 is a pedestal, 2 is an anchor device, 3 is a pressure plate, 4 is the outer side of the geotextile bag protection wall, 5 is a corrosion-resistant sleeve, 6 is a fiber-reinforced plastic (FRP), 8 is a rust-proof mortar, 9 is a corrosion-resistant sleeve and anchor cable composite anchoring body, 10 is backfill soil, 11 is an undisturbed foundation, 12 is coarse aggregate, 13 is fine aggregate, 14 is a cover water stop layer, 15 is an organic soil layer, 17 is a geogrid, 18 is a geotextile bag B unit, and 19 is a geotextile bag A unit. DETAILED DESCRIPTION

[0046] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0047] As Figure 2As shown, a slope protection system combining a multi-layer gradient capillary barrier and prestressed anchor cables includes a geotextile protective wall installed on the slope and a composite anchor body 9 consisting of a PVC anti-corrosion sleeve and an anchor cable set at an elevation angle of 4-6° to the horizontal plane. The PVC anti-corrosion sleeve is positioned on the outside of the geotextile protective wall, and the anchor cables are driven into the wall from the outside in.

[0048] In the preferred embodiment, the geotextile protective wall, backfill soil 10, and undisturbed foundation 11 are sequentially installed; the anchor cables, anti-corrosion sleeves, and anti-rust mortar form a mechanically interlocking structure with the geotextile protective wall; the anti-corrosion sleeves are positioned at the outer surface of the outer geotextile (i.e., the first geotextile) that connects to the organic soil layer (i.e., the outer surface 4 of the geotextile protective wall, equivalent to...). Figure 2 The outermost geotextile bag (the first geotextile bag) is positioned 4-6 cm above its center point on the right side. The assembly method is as follows: Assemble from the outermost geotextile bag inwards. First, install a corrosion-resistant sleeve at the point where the anchor cable will pass through. This sleeve is heat-welded to the geotextile bag. Then, ram the anchor cable into the sleeve, ensuring it is inside. Next, fill the sleeve with rust-resistant mortar, which is a mixture of mortar and a small amount of nitrite (1%–2% of the mortar mass). The anchor cable ends are connected to screw rods, which protrude outside the geotextile bag protective wall, with a length controlled within 3-5 cm. The anchor cable uses fiber-reinforced plastic (FRP) as its main body. The corrosion-resistant sleeve is made of PVC or HDPE pipe.

[0049] like Figure 1 As shown, the anchor cable includes a base 1, a bolt end rod, a pressure plate 3, an anti-corrosion sleeve 5 (with a tube body and a hollow interior), fiber reinforced plastic (FRP) material 6, and anti-rust mortar 8 (which serves as the grouting body). Figure 1 The length L of the free segment is also shown. f Except for the free section, the remaining part of the anchor cable is the anchorage section L. a .

[0050] The screw end rod is firmly connected to the anchor cable body and cooperates with the anchor 2 (such as a nut or anchor plate) to achieve the final anchoring of the anchor cable. The screw end rod is blocked by the anchor 2, so it is not in the anchor cable body. Figure 1 The component is marked in the text.

[0051] When installing the anti-corrosion sleeve, a hole is pre-drilled in the outer geotextile of the geobag, the anti-corrosion sleeve passes through the pre-drilled hole, and the connection between the anti-corrosion sleeve and the outer geotextile of the geobag is sealed and fixed by hot melting or adhesive. The outer geotextile refers to the bag body.

[0052] Further, the upper end of the earthwork bag protection wall is provided with a covering water stop layer 14, and the earthwork bag protection wall is filled with fine aggregate from top to bottom, that is, the top of the slope is a water guide layer. The covering water stop layer is formed by planting grass or laying a water stop curtain, and is composed of fine aggregate, which further enhances the water stop function of the slope protection system and prevents the infiltration of rainwater on the slope (rainfall in Fujian and other regions is large, so the slope top anti-seepage project is considered; arranging fine aggregate at the upper end can effectively prevent vertical infiltration of rainfall into the slope, so as to enable seepage along the slope).

[0053] The earthwork bag protection wall is composed of a plurality of earthwork bag capillary barrier units, each of which is sequentially arranged by a first earthwork bag filled with fine aggregate, a second earthwork bag filled with coarse aggregate, a third earthwork bag filled with fine aggregate, and a fourth earthwork bag filled with coarse aggregate, the fourth earthwork bag being larger than the first to third earthwork bags, and the first earthwork bag being connected with the soil layer; the fine aggregate or the coarse aggregate is an unsaturated soil body obtained by screening and compaction of the in-situ excavated soil body of the slope; the earthwork bag is connected with the earthwork geogrid; all the earthwork bags filled with fine aggregate form a drainage layer, and all the earthwork bags filled with coarse aggregate form a water blocking layer; the fourth earthwork bag filled with coarse aggregate is adjacent to the backfill soil.

[0054] The fine aggregate has a particle size of 0.075-0.25 mm, and 0.5%-2% nano silicon dioxide is added to the fine aggregate; the coarse aggregate has a particle size of 0.5-1 mm, and 10%-40% bentonite, 0.1%-2% organic silane, and 0.5%-2% nano silicon dioxide are added to the coarse aggregate, the mass ratio of the nano silicon dioxide to the fine aggregate being 0.5%-2%, the mass ratio of the bentonite to the coarse aggregate being 10%-40%, and the mass ratio of the organic silane to the coarse aggregate being 0.1%-2%.

[0055] The adjacent earthwork bags are connected and separated by the earthwork geogrid; all the earthwork bags filled with fine aggregate 13 form a drainage layer, and all the earthwork bags filled with coarse aggregate form a water blocking layer; the fourth earthwork bag filled with coarse aggregate 12 is adjacent to the backfill soil.

[0056] Preferably, the slope of the flow guide surface of the earthwork bag protection wall is 25-35°; and the earthwork bags of different earthwork bag capillary barrier units in the earthwork bag protection wall are arranged in a staggered manner.

[0057] From the front, in the slope protection system of the present application, the multi-layer gradient capillary barrier cooperates with the prestressed anchor cable, and the earthwork bag protection wall is composed of a plurality of earthwork bag capillary barrier units.

[0058] In the side sectional view of the slope protection system, Figure 2 the soil sample is divided in a stepped manner, and each layer of earthwork bag (a total of four) forms an earthwork bag capillary barrier unit.

[0059] From right to left, the soil samples are organic soil, fine aggregate, coarse aggregate, fine aggregate, coarse aggregate, backfill soil and undisturbed ground (where the undisturbed ground and backfill soil constitute the slope, and the backfill soil is also part of the foundation). The soil samples and the soil samples (i.e. between the geotextile bags) are separated by geogrids, and the anti-corrosion sleeve, anchor cable and mortar reinforce each layer of geotextile bag and the foundation structure. The backfill soil is selected from soil with particle size at the boundary between coarse and fine aggregate. The height of the geotextile bag protection wall is the same as that of the undisturbed ground.

[0060] Example 1

[0061] Bag: The geotextile bags included in the present application have two sizes, which are named as geotextile bag A unit 19 and geotextile bag B unit 18. Geotextile bag A unit: length 1500mm, width 600mm, height 300mm; geotextile bag B unit: length 1500mm, width 300mm, height 300mm. The first to third geotextile bags are geotextile bag B units; the fourth geotextile bag is a geotextile bag A unit.

[0062] Filler: The filler of the geotextile bag in the multi-layer gradient capillary barrier and prestressed anchor cable coordinated slope protection system is the in-situ soil of the slope (so that the filler fills the geotextile bag A unit and the geotextile bag B unit), and the in-situ excavation can greatly reduce the cost of filling the geotextile bag with soil particles. After the in-situ soil of the slope is sieved into coarse and fine aggregates, the two types of in-situ soil obtained by excavation are compacted by ramming, at which time the density of the in-situ soil of the slope increases and the integrity is enhanced; at the same time, the compaction makes the in-situ soil in a non-saturated state, and the soil in a non-saturated state has a certain water resistance; the coarse and fine aggregate soil particles are combined in a special form to play the capillary barrier effect, which has a diversion effect and can prevent rainwater and the like from infiltrating into the interior of the slope soil and causing damage to the internal structure of the slope.

[0063] Geotextile bag protection wall: formed by arranging and combining a plurality of geotextile capillary barrier units composed of geotextile bags. In principle, each geotextile capillary barrier unit is composed of three geotextile bag B units filled with aggregate and one geotextile bag A unit filled with aggregate, as seen from the cross-sectional view. Each geotextile capillary barrier unit is formed by one layer of geotextile bags stacked from left to right, which are a geotextile bag A unit filled with compacted in-situ soil (the geotextile bag fills coarse aggregate), a geotextile bag B unit (the geotextile bag fills fine aggregate), a geotextile bag B unit (the geotextile bag fills coarse aggregate) and a geotextile bag B unit (the geotextile bag fills fine aggregate); wherein each geotextile capillary barrier unit is laid horizontally outside the outer side of the geotextile capillary barrier unit above it by 0.3m (which can also be understood as Figure 2The soil bags are stacked in this way. The soil bag capillary barrier units are arranged in turn in this arrangement, and the unique arrangement can form two drainage-water barriers with large and small (large on the inside and small on the outside), so as to fully exert the capillary barrier effect of unsaturated soil, and play a role in water stopping and seepage prevention. Specifically, the first soil bag and the second soil bag form the first drainage-water barrier, and the third soil bag and the fourth soil bag form the second drainage-water barrier. Specifically, the seepage on the slope top passes through the fine-grained soil in the first soil bag on the outside of the slope, and the coarse-grained soil in the second soil bag can play a role in water stopping, thereby forming the first drainage-water barrier. When the rainfall is large, the third soil bag filled with fine-grained soil in the second layer of drainage-water barrier can play a role in drainage along the slope, and the fourth soil bag filled with coarse-grained soil can play a role in the last and most solid water stopping barrier.

[0064] A slope top water guide layer is further arranged above the first soil bag capillary barrier unit. The water guide layer is composed of three soil bag A units filled with fine aggregate.

[0065] Capillary barrier effect of unsaturated soil: In the unsaturated state, the permeability coefficient of sand decreases exponentially with the decrease of water content. The coarser the particles, the faster the rate of decrease. After excavation is completed, the in-situ soil body of the slope part is in an unsaturated state due to ramming. According to the unsaturated seepage theory, when rainfall infiltrates, the interface between the fine aggregate layer and the coarse aggregate layer generates a matric suction gradient due to the sudden change of the permeability coefficient, thereby forming a natural impermeable barrier (the measured retardation efficiency reaches 92%), which effectively controls the evolution of the seepage field of the slope. In addition, the porosity of the compacted soil is reduced, and its permeability is significantly reduced compared to before compaction. This arrangement effectively prevents deep soil saturation, thereby increasing the stability of the slope protection. In the present application, the arrangement of soil particles in the soil bag and the stacking of the soil bags are combined to form a complete capillary barrier of unsaturated soil, which can guide the flow along the slope to the slope bottom in response to rainfall and the like, thereby preventing rainfall and the like from infiltrating the slope soil.

[0066] The geotextile bag capillary barrier unit connection structure: the slope protection structure adopts the modular design concept, and the main body is constructed by standardizing the geotextile bag unit through the staggered lap joint process. Each unit is arranged in a staggered manner along the horizontal direction, and the slope protection system is optimized to a design value of 30° by accurately matching the geometric parameters of the geotextile bag unit and the staggered spacing. The angle parameter is determined based on the principle of unsaturated soil mechanics, which can fully play the characteristics of the capillary barrier structure: forming a double hydraulic barrier (water-blocking layer and drainage layer, wherein the water-blocking layer is coarse aggregate and the drainage layer is fine aggregate) on the slope surface, and building a continuous drainage channel. This structural design realizes the synergistic effect of rainfall infiltration resistance and directional drainage of pore water by regulating the distribution of matric suction. The adjacent units are separated by bidirectional tensile geogrids (nominal tensile strength ≥ 80 kN / m). In terms of layered construction: ① a standard geotextile bag fixing layer (i.e. geogrid) is arranged at the top of the geotextile bag capillary barrier unit, and a warp-knitted polyester geogrid (mesh size 40x40mm) is used for positioning and restraint. The rightmost geotextile bag B unit filled with fine aggregate reserves a grid-free construction window to ensure the smooth installation of the anchor cable; ② the bottom of the unit is fully wrapped and reinforced (i.e. the geogrid completely covers the bottom of the geotextile bag capillary barrier unit), and the lower geotextile bag is covered by high-strength polyester welded geogrid (elongation ≤ 5%) to form a continuous stress surface layer. The connection structure adopts the grid-anchor composite anchoring technology: the longitudinal geogrids (diameter ≥ 2mm) are used to realize the interlocking connection between units, and the transverse pre-stressed anchor cables are used to establish a three-dimensional constraint system. This combined structure forms a grid-like structure of the geotextile bag unit under bidirectional stress, which is verified by finite element analysis to have a shear strength 42% higher than that of the traditional structure (without using geotextile bags and capillary barriers, directly anchoring the cable for reinforcement), and the displacement control effect reaches the AA level standard of the industry. After adding the corrosion-resistant sleeve and rust-resistant mortar, the shear strength is further improved.

[0067] The geotextile bag is provided with an opening, allowing the PVC corrosion-resistant sleeve to pass through the geotextile bag and be heat-welded. The invention provides "triple corrosion protection" for the anchor cable: an integrated corrosion-resistant sleeve (such as PVC, heat-welded with the geotextile bag) is provided inside the geotextile bag at the position where the anchor cable passes through, preventing water from contacting the anchor cable; the sleeve is filled with rust-resistant mortar (adding nitrite or nano titanium dioxide), further isolating oxygen; the coarse aggregate in the geotextile bag is added with a water repellent (such as organosilane) to reduce water penetration around the anchor cable.

[0068] The present application designs a "multi-layer gradient capillary barrier" to enhance the water-blocking effect by gradient change of aggregate particle size, while adapting to the prestress distribution of anchor cable. Among them, the gradient aggregate design: the earthwork bag protective wall is from outside to inside: ① surface drainage layer (fine aggregate, particle size 0.075-0.25mm, add nano silicon dioxide, improve water permeability and anti-blocking ability); ② deep water-blocking layer (coarse aggregate, particle size 0.5-1mm, add bentonite, swell when water, enhance water-blocking effect). Set two layers of fine and coarse aggregate water stop layer. The blocking efficiency of the multi-layer gradient structure is increased, and it can adapt to the deformation of the earthwork bag caused by the prestress of the anchor cable (reduce the loosening of the aggregate). Adjust the particle size of the aggregate of the corresponding layer of the earthwork bag, set the upper layer of the earthwork bag to be thin, and the lower layer of the earthwork bag to be thick, so that the top drainage layer quickly leads away the rainwater, and avoids the corrosion of the anchor cable at the top; the bottom water-blocking layer prevents water from penetrating into the anchoring section, and maintains the friction coefficient.

[0069] The present application strengthens the "prestressed characteristics of anchor cable", and the anchor cable uses fiber reinforced plastic (FRP) (instead of steel strand), which reduces the extrusion damage to the earthwork bag (the characteristics of high strength and ductility of FRP are more matched with the earthwork bag, and the deformation coordination rate is higher).

[0070] Anchor cable: after the installation process of the earthwork bag and the PVC corrosion-resistant sleeve is completed, the anchor system construction is carried out according to the following steps:

[0071] (1) Anchor cable positioning: select the center of the PVC corrosion-resistant sleeve as the anchor cable ramming point (the grid construction window is on the outer side of the earthwork bag of part of the capillary barrier unit of the earthwork bag protective wall, the width of the window is equivalent to the ramming width of the anchor cable);

[0072] (2) Parameter design: based on the mechanical analysis of formula (5), when the anchor body diameter D increases, the rock-soil body elastic modulus E decreases in inverse proportion, resulting in a significant increase in the critical anchoring section length Lc. In order to further strengthen the "prestressed characteristics of anchor cable", 15.6mm high-strength fiber reinforced material (FRP) with 1×7 structure arrangement is determined as the anchor cable main body;

[0073] (3) Angle control: set the anchor cable to form a 5° upward angle with the horizontal plane to ensure the optimal stress transmission path;

[0074] (4) Ramming and pouring: form a mechanical interlocking structure between the anchor cable and the earthwork bag through the vibration ramming process, and then pour C50 rust-proof mortar (add nitrite) into the sleeve, so as to build a composite protection system with cooperative deformation characteristics.

[0075] (5) End treatment: weld a special screw end rod at the end of the anchor cable, the end rod is subjected to galvanized corrosion-resistant treatment, and the length of the exposed screw end rod is controlled within 3-5cm, so as to build a composite protection system with cooperative deformation characteristics.

[0076] According to the Technical Regulation of Rock Anchors (CECS 22:2005), the spacing between anchor cables should not be less than 1.5m, so the anchor cables are arranged at a spacing of not less than 1.5m.

[0077] The PVC anticorrosion sleeve, the C50 rustproof mortar, the anchor cable and the geotextile bag are integrated, so as to reinforce the geotextile bag integrated body. The quantitative relationship between the anchoring parameters and the mechanical response of the rock mass is established by the parametric design method, and the embedded sleeve-anchor-geotextile bag integrated structure is innovatively adopted, so as to form a three-dimensional space anchoring network. The screw end rod design not only ensures the connection reliability of the exposed part, but also realizes the mechanical engagement with the geotextile fabric.

[0078] The geotextile bag system is relatively rigid, can form a water-stopping and flow-guiding layer, and has low supporting strength; the anchor cable can have a free end to allow certain deformation, and the supporting strength is greatly increased after the anchor cable is combined with the PVC anticorrosion sleeve, the C50 rustproof mortar and the geotextile bag, and the defects of poor durability and easy rust are overcome. The final formed slope protection system has durability and high strength and high ductility, and effectively realizes high-strength support of the slope in an extreme condition (rainfall infiltration working condition) at low cost. The slope protection structure is suitable for high-slope and high-hazard slope protection engineering in mountainous and hilly regions such as Fujian.

[0079] The surface green plant slope protection structure: due to the existence of the slope gradient, the organic soil part is exposed in a stepped manner, so as to facilitate the planting of green plants. The organic soil layer is consistent with the original angle of the slope.

[0080] As can be seen from the above examples, the slope protection system with the multi-layer gradient capillary barrier and the prestressed anchor cable has a wide application range, good application prospect and rich practical value. It not only can effectively improve the safety and stability of civil engineering, but also meets the environmental protection requirements, and is a slope engineering protection method worthy of promotion and application.

[0081] The above examples are only used to illustrate the technical solutions of the present application, and those skilled in the art should understand that the above examples do not limit the present application in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. A multi-layer gradient capillary barrier in conjunction with a pre-stressed cable for slope protection system, characterized in that, The soil bag protection wall is arranged on the slope, and the anchor cable is arranged at an angle of 4-6 degrees with the horizontal plane, the ramming position of the anchor cable is the outer side of the soil bag protection wall, and the extension direction of the anchor cable is from the outside to the inside.

2. A multi-layered gradient capillary barrier in conjunction with pre-stressed cable for slope protection system according to claim 1, characterized in that, The soil bag protection wall, backfill soil and undisturbed foundation are sequentially arranged; the anchor cable, the corrosion-proof sleeve and the rust-proof mortar form a mechanical interlocking structure with the soil bag protection wall; the ramming position of the anchor cable is 4-6 cm above the center point of the outer surface of the soil bag connected with the organic soil layer; the assembly mode of the corrosion-proof sleeve and the anchor cable composite anchoring body is: from the outer side of the soil bag to the inside, the corrosion-proof sleeve is arranged at the position to be passed through by the anchor cable, the corrosion-proof sleeve is hot-welded with the soil bag, the anchor cable is rammed into the corrosion-proof sleeve, then the rust-proof mortar is filled into the corrosion-proof sleeve, the rust-proof mortar is mixed by mortar and a small amount of nitrite, the addition amount of the nitrite is 1%-2% of the mass of the mortar; the end of the anchor cable is connected with a screw end rod, the screw end rod is exposed outside the soil bag protection wall; the anchor cable uses fiber reinforced plastic (FRP) as the main body of the anchor cable; the corrosion-proof sleeve is a PVC or HDPE pipe.

3. A multi-layered gradient capillary barrier in conjunction with pre-stressed cable for slope protection system according to claim 2, characterized in that, When the corrosion-proof sleeve is installed, a pre-opening is pre-opened on the outer soil fabric of the soil bag, the corrosion-proof sleeve passes through the pre-opening, and the connection between the corrosion-proof sleeve and the outer soil fabric of the soil bag is sealed and fixed by hot melting or adhesive; the outer soil fabric refers to the bag body; the upper end of the soil bag protection wall is provided with a covering water stop layer, and the first layer of soil bags from top to bottom of the soil bag protection wall are all soil bags filled with fine aggregate; the covering water stop layer covers the first layer of soil bags.

4. The multi-layered gradient capillary barrier in conjunction with pre-stressed cable system for slope protection of claim 1, wherein, The soil bag protection wall is composed of a plurality of soil bag capillary barrier units, each soil bag capillary barrier unit is sequentially arranged by a first soil bag filled with fine aggregate, a second soil bag filled with coarse aggregate, a third soil bag filled with fine aggregate, and a fourth soil bag filled with coarse aggregate, the fourth soil bag is larger than the first to third soil bags, and the first soil bag is connected with the organic soil layer; the fine aggregate or the coarse aggregate is an unsaturated soil body obtained by screening and compaction of the in-situ excavated soil body of the slope; the soil bag is connected with a geogrid; all soil bags filled with fine aggregate form a drainage layer, and all soil bags filled with coarse aggregate form a water-blocking layer; the fourth soil bag filled with coarse aggregate is adjacent to the backfill soil. The particle size of the fine aggregate is 0.075-0.25 mm, 0.5%-2% nano silicon dioxide is added to the fine aggregate; the particle size of the coarse aggregate is 0.5-1 mm, 10%-40% bentonite, 0.1%-2% organic silane, 0.5%-2% nano silicon dioxide, 10%-40% bentonite, and 0.1%-2% organic silane are added to the coarse aggregate; the mass ratio of nano silicon dioxide to fine aggregate is 0.5%-2%, the mass ratio of bentonite to coarse aggregate is 10%-40%, and the mass ratio of organic silane to coarse aggregate is 0.1%-2%.

5. The multi-layered gradient capillary barrier in conjunction with pre-stressed cable system for slope protection of claim 1, wherein, The slope of the flow guide surface of the soil bag protection wall is 25-35 degrees; the soil bags of different soil bag capillary barrier units in the soil bag protection wall are arranged in a staggered manner.

6. A multi-layered gradient capillary barrier in conjunction with a pre-stressed cable for slope protection system according to claim 4, wherein, The anticorrosion sleeve is inserted from the center point of the outer surface of the outer geotextile bag connected with the organic soil layer of a geotextile bag capillary barrier unit to a position 4-6 cm above the center point, and sequentially passes through the other three geotextile bags of the geotextile bag capillary barrier unit, the anchor cable is inserted into the anticorrosion sleeve, the anticorrosion sleeve is filled with rust-proof mortar between the anchor cable, and the anchor cable is finally anchored in the backfill soil; the anchor cable and the anticorrosion sleeve are located in the four geotextile bags of the geotextile bag capillary barrier unit, and the end of the anchor cable is anchored in the backfill soil.

7. A method for constructing a slope protection system of a multi-layer gradient capillary barrier in cooperation with a pre-stressed anchor cable according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: a. Hot welding the anticorrosion sleeve with the geotextile bag, the diameter of the anticorrosion sleeve is 9-11 cm, the center of the anticorrosion sleeve is located 5 cm above the center point of the outer surface of the outer geotextile bag connected with the organic soil layer, and the anticorrosion sleeve forms an angle of 5° with the horizontal plane; the fine aggregate or coarse aggregate obtained by screening and compaction of the in-situ excavated soil of the slope is mixed with nano-silicon dioxide, bentonite and organosilane respectively, and then filled into the geotextile bag body, and sealed; b. Using the geogrid, a plurality of geotextile bags are connected through the geogrid to form a continuous geotextile bag protection wall; c. Using the anchor cable, the anchor cable is rammed at the center of the anticorrosion sleeve, the anchor cable forms an angle of 5° with the horizontal plane, C50 rust-proof mortar mixed with nitrite is poured into the anticorrosion sleeve, and the end of the anchor cable is welded with a screw end rod; part of the screw end rod is exposed outside the geotextile bag; d. The geotextile bag protection wall is placed at the position to be protected, and the position to be protected includes the river bank or the slope.

8. The construction method according to claim 7, characterized in that, The anchor cable body is made of fiber reinforced plastic (FRP).

9. The construction method according to claim 7, characterized in that, The construction steps of the anchor cable are as follows: (1) Anchor cable positioning: the center of the anticorrosion sleeve is selected as the anchor cable ramming point; (2) Anchor cable body determination: 15.6 mm high-strength fiber reinforced plastic (FRP) arranged in 1×7 structure is used as the anchor cable body; (3) Angle control: the anchor cable forms an angle of 5° with the horizontal plane, so that the setting angle of the anchor cable is parallel to the anticorrosion sleeve; (4) Assembly construction: the anchor cable and the geotextile bag form a mechanical interlocking structure through vibration ramming; (5) Grouting body pouring: after the anchor cable is rammed, C50 mortar containing nitrite is poured into the anticorrosion sleeve; (6) End treatment: a screw end rod is welded at the end of the anchor cable, the screw end rod is subjected to galvanizing anticorrosion treatment, and the length of the screw end rod exposed outside the geotextile bag is controlled within the range of 3-5 cm.

10. The construction method according to claim 7, characterized in that, The anchor cable pedestal, screw end rod and pressure bearing plate are exposed outside the geotextile bag; the outside of the geotextile bag protection wall is covered with organic soil.

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