Giant stone anchoring matrix type debris flow blocking structure and construction method thereof

Abstract

The invention belongs to the field of debris flow impact prevention and control, and particularly relates to a giant stone anchoring matrix type debris flow blocking structure and a construction method thereof. The giant stone anchoring matrix type debris flow blocking structure comprises at least three rows of giant stone anchor cable structures arranged in a channel of a debris flow circulation area, and the giant stone anchor cable structures are arranged in the channel in a quincunx shape or a rectangle shape to form a system blocking group. The construction method of the giant stone anchoring matrix type debris flow blocking structure comprises the steps of cleaning a channel unconsolidated bed, moving the giant stones, installing the NPR anchor cables, tensioning the anchor cable steel strands and the like. According to the invention, the original giant stone source of the channel is innovatively constructed into a blocking structure group, so that the motion control of the giant stone can be realized, and the disaster scale is reduced; meanwhile, the constant-resistance large-deformation mechanical property of the giant NPR anchor cable is utilized, the gravitational force of the giant stone can be utilized to the maximum extent to intercept material source particles, the continuous material source deposition effect is formed in a debris flow channel, solid particles are intercepted, and the debris flow disaster scale is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of debris flow impact prevention and control, and in particular relates to a boulder anchored matrix type debris flow blocking structure. Background Art

[0002] Debris flow is a natural disaster caused by the movement of solid-liquid two-phase bodies under the action of gravity and hydrodynamics. In recent years, extreme weather and earthquake events have caused a sharp increase in the scale of debris flow disasters, bringing huge challenges to the field of debris flow prevention and control engineering. The impact of boulders carried by debris flow is the main factor causing damage to buildings and prevention and control structures. According to investigations, in the Sanyangou debris flow disaster in Zhouqu, Gansu, the strong earthquake caused a large number of boulders larger than 1 meter to remain in the ditch. The maximum size of the boulders carried by the debris flow reached 12.9m×8.6m×7.2m, causing damage to 9 retaining structures in the ditch. The prevention and control of the impact of boulders in debris flow has become a difficult point in the prevention and control of debris flow disasters due to the great uncertainty and high-intensity impact of the boulders.

[0003] In order to reduce the impact damage of debris flow, rigid structures constructed with mortar masonry and reinforced concrete, such as retaining dams, grating dams, gap dams, valley squares, anti-impact rib walls, sand storage reservoirs, stepped channels, diversion dikes, etc.; and flexible nets constructed with reinforced materials, such as flexible retaining nets and gabions, are comprehensively used in the prevention and control of debris flow disasters. In order to meet the safety reserve of boulder impact, a large number of debris flow prevention and control structures need to be built. If traditional dams and protective net projects are used, in addition to requiring a large amount of construction materials, a large number of rigid structures will also have an adverse effect on the ecological environment of debris flow valleys. In terms of using natural materials to construct debris flow prevention and control structures, it is commonly used to fill the channel with pebbles to form channel protection, or to form a natural protection system with stepped deep pools through channel boulders. However, these boulder structures mainly rely on their own gravity or the joint locking of boulders / binge cages to achieve system stability, and there is a possibility of being swept away by debris flow.

[0004] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a boulder-anchored matrix debris flow barrier structure, which uses the gravity of natural boulders and the constant resistance and large deformation characteristics of NPR anchor cables to anchor natural boulders to the bedrock of the ditch bed, and realizes dual control of boulder movement and solid particle deposition through matrix layout, thereby achieving the purpose of reducing debris flow impact disasters.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] At least three rows of boulder anchor cable structures in the channel of the flow zone, wherein the boulder anchor cable structures are arranged in a quincunx shape or a rectangular shape in the channel to form a system barrier group;

[0008] The boulder anchor cable structure includes an anchoring structure fixed in the ditch bed, an NPR anchor cable and a boulder with a size not less than 1.5m×1.5m×1.5m. The NPR anchor cable includes an anchor cable steel strand, an anchor assembly, a constant resistance sleeve and a constant resistance body located in the constant resistance sleeve. The constant resistance sleeve is fixed in the boulder, the first end of the anchor cable steel strand passes through and is fixed in the constant resistance body, and the second end of the anchor cable steel strand is fixed to the anchoring structure through the anchor assembly.

[0009] Furthermore, the length of the anchor cable steel strand is greater than 8.0m and less than 30m; the angle between the extension direction of the anchor cable steel strand and the ditch bed is 15° to 30°; and the tension load of the anchor cable steel strand is 90% of the tensile strength of the anchor cable.

[0010] Furthermore, the anchoring force of the NPR anchor cable is not less than the designed anchoring force of the anchor cable, and the designed anchoring force of the anchor cable is:

[0011]

[0012] Where: T k is the anchorage force of the anchor cable, m b is the mass of the boulder, g is the acceleration of gravity, θ is the slope of the ditch bed, μ is the friction coefficient between the ditch bed and the boulder, α d is the debris flow impact correction coefficient, which is generally taken as 1.0~1.5; ρ is the debris flow density, v is the debris flow movement speed, and a and b are the side lengths of the boulder facing the water respectively.

[0013] Furthermore, the distance between the boulders and the edge of the channel is not less than 3.0m, the distance between adjacent boulders in the same row is not less than 1.0m and not more than 0.7 times the size of the largest boulder; the distance between two adjacent rows of boulders is 3 to 4 times the average size of the two rows of boulders, and the maximum does not exceed 2.5 times the size of the largest boulder in the two rows.

[0014] Furthermore, the anchor cable steel strands are multiple 1×7 unbonded prestressed steel strands, each of which is sheathed with a corrugated tube; all the anchor cable steel strands are passed through a casing, a first end of the casing is fixed in a boulder, an anchor cable isolation bracket is installed at the second end of the casing, some of the anchor cable isolation brackets extend beyond the casing and are installed with casings, and the casing is fixed in an anchoring structure; the middle part of the casing is erected on the bedrock of the ditch bed through a pier.

[0015] Furthermore, the anchoring structure includes an anchor arranged in the bedrock of the trench bed.

[0016] Furthermore, the anchoring structure includes an anchor stone, which is a stone existing in the channel with a size of 1.5m×1.5m×1.5m or more. The anchoring assembly is an NPR anchor cable constant resistance structure fixed in the anchor stone, so that the boulder anchor cable structure forms a boulder tension anchor cable structure.

[0017] Furthermore, the boulder-anchored matrix debris flow retaining structure is arranged in the middle and upper reaches of the main ditch and the middle and lower reaches of the branch ditch in the debris flow flow area; the size range of the boulders is 1.5m×1.5m×1.5m~6m×6m×6m, and the ratio of the sum of the spacing between boulders in the same row to the channel width is 0.4~0.7.

[0018] The present invention also proposes a construction method using the boulder anchoring matrix type debris flow retaining structure, comprising the following steps:

[0019] (1) Design the anchoring structure and boulder location; clean the loose layer in the channel and move the boulder to the predetermined location; calculate the location of the hole in the boulder for installing the constant resistance sleeve, and construct the hole and anchoring structure;

[0020] (2) Pass the first end of the anchor cable strand through the hole and out of the boulder, install the constant resistance sleeve and constant resistance device in sequence, and then tension the anchor cable strand;

[0021] (3) When the tension of the anchor cable steel strand reaches the design strength, anchor the first end of the anchor cable steel strand.

[0022] Furthermore, a single anchor cable steel strand is tensioned in stages, with each stage of tensioning load being 0.25, 0.5, 0.75, and 1.2 times the design tension. Each stage needs to be stable for 5 to 10 minutes, and the last stage needs to be stable for 2 to 3 days. When the tension reaches the design strength, the anchor cable is locked. The design tension is 75% of the tensile strength of the anchor cable.

[0023] The working principle of the present invention is to utilize the constant resistance and large deformation mechanical characteristics of NPR anchor cables to anchor natural boulders to the bedrock of the ditch, and to realize boulder movement and solid particle deposition effects through matrix layout, thereby consuming the kinetic energy of the debris flow impact process and achieving the purpose of reducing debris flow impact disasters.

[0024] (a) When the debris flow impact begins, the NPR anchor cable begins to respond. When the impact pressure and the intercepted particle load do not exceed 75% of the tensile strength of the anchor cable, the boulder basically does not move and continues to intercept solid particles;

[0025] (b) When the impact pressure and interception particle load (P) exceed the constant resistance design of the NPR anchor cable, the constant resistance body of the NPR anchor cable begins to displace and continuously resists the impact through displacement deformation. At this time, the boulder may produce a small amount of displacement and cause part of the sediment to be lost;

[0026] (c) When the impact continues, the movement of the constant resistance body causes it to fall out of the sleeve, and the deformation of the NPR anchor cable stops. At this stage, the structural system can still resist the impact continuously. The system resistance comes from the tensile strength of the steel strand anchor cable until the anchor cable steel strand separates from the boulder and the system fails.

[0027] From the analysis of the force conditions of boulders, their movement is controlled by gravity, buoyancy, fluid drag, ditch bed friction and impact. Under the same boulder conditions, the increase in debris flow density leads to an increase in buoyancy and drag on the boulders and a decrease in friction, and the movement of the boulders accelerates. Conversely, when the density of debris flow decreases, the movement of the boulders tends to decelerate. On the basis of controlling the movement of boulders, intercepting coarse particles reduces the density of debris flow, reduces the probability of entrainment of active sources of ditch bank collapse, and reduces the ability of newly added boulders to entrain loose particles, thus achieving the protection goal.

[0028] Theoretically, the prevention and control structure will become a new source of material after failure. Therefore, when the megalithic structure is laid out in the main ditch, it needs to be located upstream of the debris flow deposition area and needs to be systematically laid out with the downstream retaining dam structure (or another set of megalithic anchored matrix type debris flow retaining structure layout).

[0029] The beneficial effects of the present invention are:

[0030] The present invention utilizes a large number of boulders to pile up in the debris flow channel, which can realize the control of the movement of boulders and reduce the scale of disasters; at the same time, by utilizing the constant resistance and large deformation mechanical characteristics of the giant NPR anchor cable, the gravity of the boulders can be utilized to the greatest extent to intercept the source particles, forming a continuous source deposition effect in the debris flow channel.

[0031] Compared with the existing debris flow barrier structure, the present invention realizes the transformation and utilization of boulder impact damage, innovatively constructs the original boulder source in the channel into a barrier structure group, intercepts solid particles and reduces the scale of debris flow disasters. It is a new green, efficient and energy-saving debris flow barrier structure technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0033] Figure 1 Schematic diagram of the arrangement of embodiment 1 of the present invention Figure 1 .

[0034] Figure 2 Schematic diagram of the arrangement of embodiment 1 of the present invention Figure 2 .

[0035] Figure 3 This is a schematic diagram of the arrangement of embodiment 2 of the present invention.

[0036] Figure 4This is a schematic diagram of the arrangement of embodiment 2 of the present invention.

[0037] Figure 5 This is a schematic structural diagram of the boulder anchor structure of Example 1 of the present invention.

[0038] Figure 6 Schematic diagram of the top view of the boulder anchor structure of Example 1 of the present invention.

[0039] Figure 7 This is a schematic structural diagram of the boulder anchor structure of Example 2 of the present invention.

[0040] Figure 8 This is a diagram of the experimental arrangement of a verification example of the present invention.

[0041] Fig. 9 This is a diagram showing the arrangement of impact force monitoring points for the rigid dam body in the verification example of the present invention.

[0042] Fig.10 This is a deployment diagram of a simulated retaining structure for a verification example of the present invention.

[0043] Fig.11 This is a diagram of the flow channel deposition results of a verification example of the present invention.

[0044] Fig.12 This is a structural diagram of the peak impact force of the rigid dam body of the verification example of the present invention.

[0045] In the figure: 11-anchor body, 12-anchor block, 13-first gasket, 14-sleeve, 15-first anchor cable lock, 16-anchor, 17-anchor cable isolation bracket, 18-anchor stone, 21-casing, 22-centering device, 23-pier, 27-anchor cable strand, 31-boulder, 32-channel, 33-anchor pad, 34-constant resistance sleeve, 35-constant resistance, 36-second gasket, 38-second anchor cable lock, 41-source box, 42-valve, 43-rigid dam body, L1-edge spacing, L2-spacing in the same row, L3-distance between rows. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0047] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0048] like Figures 1 to 7As shown, a boulder anchoring matrix type debris flow barrier structure includes at least three rows of boulder anchor cable structures arranged in a channel in a debris flow flow area;

[0049] The boulder anchor cable structure includes an anchoring structure fixed in the ditch bed, an NPR anchor cable and a boulder 31 with a size not less than 1.5m×1.5m×1.5m. The NPR anchor cable includes an anchor cable steel strand 27, an anchor assembly, a constant resistance sleeve 34 and a constant resistance body located in the constant resistance sleeve 34; the constant resistance sleeve 34 is fixed in the boulder 31, the first end of the anchor cable steel strand 27 passes through and is fixed in the constant resistance body, and the second end of the anchor cable steel strand 27 is fixed to the anchoring structure through the anchor assembly.

[0050] The boulder anchor cable structure uses NPR anchor cables as the main load-bearing components. NPR anchor cables can continuously maintain a constant resistance of about 350 kN under tension. The boulders 31 are fixed to the channel through NPR anchor cables to form boulder anchor cable units. The units can be arranged in a matrix or plum blossom form in the valley to form a system barrier group.

[0051] The boulder-anchored matrix debris flow barrier structure of the present invention utilizes natural boulders 31 to reduce the impact destructiveness of debris flow. It should be noted that, affected by the randomness of the size and spatial arrangement of the existing boulders 31 in the channel, the boulder-anchored matrix debris flow barrier structure of the present invention is not strictly and accurately arranged in a rectangular or plum blossom-shaped matrix, but when the ratio of the size of the boulder 31 to the channel width is large, the boulder 31 must be cut to balance the scale of the boulder-anchored matrix debris flow barrier structure to form a multi-structure system, avoid arranging the boulders 31 upstream of the narrow channel, and prevent the debris flow from forming a dam in front of the boulder 31.

[0052] The boulder-anchored matrix type debris flow barrier structure should be set up in the middle and upper reaches of the main ditch and the middle and lower reaches of the branch ditch in the debris flow area. The ratio of the selected maximum boulder 31 size to the groove width is generally 0.05-0.1. For boulders 31 with existing sizes greater than 1.5m in the channel, transportation should be minimized. For oversized boulders 31, cutting can be used; when the ratio of the boulder 31 size to the groove width is too low, the boulder 31 needs to be transported to achieve a system effect, otherwise it only serves to fix the boulders 31, but cannot achieve the effect of debris flow prevention and control. The layout parameters (quantity, spacing, NPR structural parameters) of the boulder-anchored matrix type debris flow barrier structure should be designed based on the debris flow classification, the primary outflow flow, the source particle grading and the layout location.

[0053] Similar to other steel or reinforced concrete baffle structures, the boulder NPR anchor cable structure system can also be used as a buffer structure in front of a dam for granular or debris flows. It can be combined with the loose body soil discharge scheme, first laid inside the loose rock and soil, and after layered rolling, a reinforcement effect is formed inside the loose body to improve stability.

[0054] Further, such as Figure 1 As shown, the distance between the boulder 31 and the edge of the channel is not less than 3.0m, the distance between adjacent boulders 31 in the same row is not less than 1.0m and not more than 0.7 times the size of the largest boulder 31; the ratio of the sum of the distances between boulders 31 in the same row to the channel width is 0.4-0.7; the distance between two adjacent rows of boulders 31 is 3-4 times the average size of the two rows of boulders 31, and the maximum does not exceed 2.5 times the size of the largest boulder 31 in the two rows. In practice, since the boulders 31 are made from local materials, the sizes of the boulders 31 are different, and the size of a single boulder 31 is 1.5m-6.0m. From the overall point of view, the boulder anchor matrix debris flow barrier structure is arranged in steps, and the boulders 31 in the same row are arranged in a single step. For example, in the same row, the sizes of adjacent boulders 31 are 1.5m and 3.0m respectively, then the maximum gap between the boulders 31 should not exceed 3.0m×0.7=2.1m. For example, the sizes of the Nth row of boulders 31 are 1.5m, 2m, and 2.5m respectively, and the sizes of the N+1th row of boulders 31 are 2.5m, 3m, and 3.5m respectively, that is, the average size of the two rows of boulders 31 is 2m and 3m, then 3 to 4 times the average size of the two rows of boulders 31 is 7.5 to 10m, and 2.5 times the size of the largest boulder 31 is 8.75m, so the distance between the two rows of boulders 31 is 7.5 to 8.75m. For another example, the sizes of the Nth row of boulders 31 are 1.5m, 2m, and 2.5m, respectively, and the sizes of the N+1th row of boulders 31 are 5m, 5.5m, and 6.0m, respectively, that is, the average size of the two rows of boulders 31 is 2m and 5.5m, then 3 to 4 times the average size of the two rows of boulders 31 is 11.25 to 15m, and 2.5 times the size of the largest boulder 31 is 15m, so the distance between the two rows of boulders 31 is 7.5 to 8.75m.

[0055] The anchor cable strand 27 is arranged along the general extension direction of the channel, and the angle between the anchor cable strand 27 and the flow direction of the debris flow cannot exceed 15°; the length of the anchor cable strand 27 is greater than 8.0m and less than 30m, and the length of the strand is calculated based on the angle and the longitudinal spacing of the boulder anchor cable structure; the angle between the anchor cable strand 27 and the channel bed is 15° to 30°. The tension load of the anchor cable strand 27 is 90% of the tensile strength of the anchor cable. The anchor cable strand 27 uses high-strength and low-relaxation steel strands, and the specifications of the steel strands should comply with GB / T 5224; the anchoring force of the NPR anchor cable is not less than the designed anchoring force of the anchor cable, and the designed anchoring force of the anchor cable is:

[0056]

[0057] Where: T k is the anchorage force of the anchor cable, m b is the mass of the boulder, g is the acceleration of gravity, θ is the slope of the ditch bed, μ is the friction coefficient between the ditch bed and the boulder, α d is the debris flow impact correction coefficient, which is generally taken as 1.0~1.5; ρ is the debris flow density, v is the debris flow movement speed, and a and b are the side lengths of the boulder facing the water respectively.

[0058] Specifically, the anchor cable strand 27 is a plurality of 1×7 unbonded prestressed strands; the diameter Φ=15.24 mm, and the tensile strength design value f of the prestressed strand is py =1320MPa, strength standard value f ptk =1860MPa; the number of prestressed steel strands is selected according to the "Design Code for Landslide Prevention and Control"

[0059] (GB / T38509-2020) stipulates:

[0060]

[0061] Where: n is the number of steel strands that make up the anchor cable, in units of roots; F b is the safety factor of anchor cable pullout, which is taken as 2.0; T k The anchoring force for the anchor cable is designed based on the weight of the boulder 31 and the topographic and geological conditions of the channel. m is the anchor efficiency coefficient, which takes a value of 0.95; F m It is the maximum force of a single steel strand.

[0062] The present invention also proposes a construction method of a boulder-anchored matrix debris flow retaining structure, comprising the following steps:

[0063] (1) Design the anchoring structure and the position of the boulder 31; clean the loose layer in the channel and move the boulder 31 to the predetermined position; calculate the position of the hole 32 in the boulder 31 for installing the constant resistance sleeve 34, and construct the hole 32 and the anchoring structure;

[0064] (2) The first end of the anchor cable strand 27 is passed through the hole 32 and out of the boulder 31, and the constant resistance sleeve 34 and the constant resistor 35 are installed in sequence, and then the anchor cable strand 27 is tensioned; a single anchor cable strand 27 is tensioned in stages, and the tensioning load of each stage is 0.25, 0.5, 0.75, and 1.2 times the design tension. Each stage needs to be stable for 5 to 10 minutes, and the last stage needs to be stable for 2 to 3 days; when the tension reaches the design strength, the anchor cable is locked; the design tension is 75% of the tensile strength of the anchor cable;

[0065] (3) When the tension of the anchor cable steel strand 27 reaches the designed strength, the first end of the anchor cable steel strand 27 is anchored.

[0066] The foundation of the anchoring system is similar to the foundation design of a general prevention and control structure, and is determined by the size of the boulder 31, the type of anchor cable, and the topographic and geological conditions of the channel. The boulder 31 is large in size and the anchor cable has a large tension, so the foundation of the anchoring system requires higher requirements, and the channel bed with a smaller loose layer thickness should be selected as much as possible to lay the anchoring system. When the loose layer of the local stratum is thin, it is necessary to remove the loose layer and enter 1m of the medium-weathered bedrock; when the loose layer is thick and the removal cost is too high, it can be completed through foundation treatment technology, and the design can refer to the "Technical Specifications for Building Foundation Treatment" JGJ 79-2012. The present invention provides two types of anchoring structure embodiments, which are described below.

[0067] Example 1

[0068] In this embodiment, the anchoring structure is based on a concrete anchor 16 .

[0069] like Figure 5 , Figure 6 As shown, the anchoring structure includes an anchor 16, a steel sleeve 14, a cable anchor isolation bracket for separating multiple anchor cable strands 27 in an orderly manner, a first anchor cable lock 15, a first washer 13, an anchor block 12, and an anchor body 11.

[0070] The construction process is:

[0071] Clean the loose layer in the channel and move the boulder 31 to the predetermined position; design the installation position of the constant resistance sleeve 34 based on the position of the anchor 16 and the boulder 31, and perform the drilling construction of the hole 32 of the boulder 31; install the NPR constant resistance structure (including the constant resistance sleeve 34 and the constant resistor 35 and other necessary devices, etc.);

[0072] After excavating the foundation, the anchor 16 foundation and the concrete anchor body 11 are constructed, and a steel sleeve 14 is pre-buried on the upper part of the concrete anchor body 11; when the anchor body concrete 11 reaches a certain strength, the anchor cable steel strand 27 is installed; the angle between the anchor cable steel strand 27 and the ditch bed is 15° to 30°, and the length of the steel strand is calculated based on the angle and the longitudinal spacing of the boulder anchor cable structure. The angle between the steel strand of the boulder anchor cable structure and the flow direction of the debris flow shall not exceed 15°;

[0073] First, the first end of the anchor cable strand 27 is installed in the NPR constant resistance structure in the boulder 31; the second end of the anchor cable strand 27 passes through the corrugated pipe, stainless steel or steel casing 21, sleeve 14 and anchor block 12; one end of the casing 21 is fixed to the hole 32 of the boulder 31 with a second washer 36; the other end of the casing 21 is installed with an anchor cable isolation bracket 17 and connected to one end of the sleeve 14, and the first washer 13 is used to install the casing 21 in the anchor 16 / sleeve 14; centering devices 22 are arranged at regular intervals in the casing 21, and the anchor cable strand 27 passes through each centering device 22 in turn, and the centering device 22 is used to straighten the anchor cable strand 27 in the casing 21.

[0074] The anchor block 12 is covered on the other end of the sleeve 14, and then the second end of the anchor steel strand 27 is tensioned and fixed on the anchor block 12 with the first anchor lock 15, and the excess part of the anchor steel strand 27 at the outlet position is cut off; after the sleeve 14 and the anchor steel strand 27 are treated with grease for corrosion protection, the inside of the sleeve 14 is poured to close the anchoring structure; the position of the pier 23 is selected according to the terrain of the channel and the length of the casing 21, and the pier 23 can be a concrete pier 23 or a steel pier 23.

[0075] Figure 1 and Figure 2 This is a typical layout diagram of the plum blossom matrix of the boulder anchor matrix type debris flow retaining structure of this embodiment. Figure 1 L1 represents the distance between the boulder 31 and the edge of the channel, L2 represents the distance between adjacent boulders 31 in the same row, and L3 represents the distance between two adjacent rows of boulders 31; that is, L1 ≥ 3.0 m; L2 ≥ 1.0 m, L2 is not greater than 0.7 times the size of the largest boulder 31; L3 is 3 to 4 times the average size of the boulders 31 in the two adjacent rows, and the maximum does not exceed 2.5 times the size of the largest boulder 31 in the two rows.

[0076] The constant resistance large deformation anchor cable in this embodiment can also be replaced by a simple prestressed anchor cable, but the service life of the system is reduced and the stability is reduced.

[0077] Example 2

[0078] When the channel strata are loose and thick, and there are many large boulders 31, the anchoring system can use the existing boulders 31 in the channel to replace them, forming a boulder 31 pulling anchor cable structure. When the upstream coarse-grained material is continuously deposited in the gaps between the boulders 31, a "bed" is formed. The bed-laying effect will lead to the drag reduction effect of laminar flow and accelerated movement, reducing the scale of debris flow disasters.

[0079] like Figure 7As shown, in this embodiment, the anchoring structure includes an anchor stone 18, which is a stone existing in the channel with a size of 3.0m×3.0m×3.0m or more, and should be at least 2.0 times larger than the size of the boulder 31. The anchoring assembly is an NPR anchor cable constant resistance structure fixed in the anchor stone 18, that is, both ends of the anchor cable steel strand 27 are fixed in the boulder 31 using an NPR anchor cable constant resistance structure, so that the boulder anchor cable structure formed by the boulder 31 and the anchor stone 18 in this embodiment constitutes a boulder 31 tension anchor cable structure; therefore, the line connecting the layout positions of the anchor stone 18 and the boulder 31 should be consistent with the flow or intersect at a small angle, and the angle shall not be greater than 15°.

[0080] The present invention aims at the impact prevention and control technology of debris flow, especially the problem of controlling the movement of boulders 31 in the channel, and provides a method of anchoring the boulders 31 in the channel by using NPR anchor cable structures. By arranging the boulders 31 in a matrix in the channel, the movement of the boulders 31 can be controlled while intercepting the debris flow source, increasing the movement resistance of the debris flow source, and reducing the impact destructiveness of the debris flow.

[0081] The construction process is:

[0082] According to the position of the existing boulder 31 in the channel, the boulder 31 and the anchor stone 18 are selected and adjusted, and the direction of the steel strand and the installation position of the two NPR constant resistance structures are designed;

[0083] The first end of the anchor cable strand 27 is installed in the NPR constant resistance structure in the boulder 31; the second end of the anchor cable strand 27 passes through the corrugated pipe, stainless steel or steel casing 21, sleeve 14 and anchor block 12; one end of the casing 21 is fixed in the hole 32 of the anchor stone 18 by the first washer 13, and one end of the casing 21 is fixed in the hole 32 of the boulder 31 by the second washer 36, so that the hole 32 in the anchor stone 18 and the boulder 31 is connected with the casing 21 to form a channel for the anchor cable strand 27, and the connection between the hole 32 and the casing 21 is sealed by the first washer 13 and the second washer 36 respectively; the casing 21 is provided with centering devices 22 at certain intervals, and the anchor cable strand 27 passes through each centering device 22 in turn, and the centering device 22 is used to separate and straighten the anchor cable strand 27 in the casing 21;

[0084] After the anchor cable strand 27 is tensioned, it is fixed on the constant resistance body of the NPR constant resistance structure in the anchor stone 18, and the exposed excess anchor cable strand 27 is cut off; after the constant resistance sleeve 34 and the anchor cable strand 27 are treated with grease for corrosion protection, the opposite ends of the constant resistance sleeve 34 are sealed with a plugging structure to prevent rainwater and debris from entering the constant resistance sleeve 34. The position of the pier 23 is selected according to the terrain of the channel and the length of the casing 21. The pier 23 can be a concrete pier or a steel pier.

[0085] Figure 3This is a boulder anchor matrix type debris flow barrier structure in the form of a plum blossom matrix in this embodiment. In actual construction, according to the position of the existing boulders 31 in the channel, the following can be used: Figure 4 The matrix retaining structure of the embodiment 1 shown in the figure, which uses anchors 15 to anchor the boulder, and the boulder 31 in this embodiment, which is a mixed arrangement of the anchor cable structure. Figures 1 to 4 The hollow arrow in the figure indicates the flow direction of the debris flow.

[0086] Verification Example

[0087] In order to illustrate the effect of the present invention, a similar simulation experiment was carried out indoors.

[0088] Experimental design: Figure 8-Figure 11 As shown in the figure, the boulder-anchored matrix debris flow barrier structure is arranged in a rectangular water tank with an inclination angle of 19° and a size of 4000mm×400mm×600mm. The top of the water tank has a volume of 0.6m 3 The source box 41 is provided with a valve 42 to control the release of debris flow sources. The end of the water tank is connected to a deposition platform with a size of 1400mm×800mm×300mm, and a rigid dam body 43 is provided at the end of the platform. Sensors are arranged on the water-facing surface of the rigid dam body 43 to monitor the impact intensity of the debris flow.

[0089] In natural debris flows, the ratio of the size of boulder 31 to the width of the debris flow channel rarely exceeds 0.1-0.2, and is generally between 0.02-0.05; the ratio of the maximum boulder 31 size to the debris flow depth does not exceed 0.2-0.5; therefore, the size of the experimental boulder 31 is designed to be 5.0 cm. Debris flows contain particles from colloids, silts, clay, gravel and pebbles. In this verification example, the debris flow source boulder 31 is simulated by natural pebbles (marked in red and blue), and the anchoring boulder 31 is simulated by cubic sandstone with a side length of 5 cm. The debris flow source is composed of soil particles of 6 particle groups, and the particle grading curvature coefficient C c =2.38, particle unevenness coefficient C u =10.5; the proportions of various particle groups are: S1 coarse gravel (20-25mm, 20%), S2 medium gravel (10-0mm, 30%), S3 medium gravel (5-10mm, 20%), S4 fine gravel (1-5mm, 10%), S5 fine sand (0.075-1mm, 3%) and S6 silt (less than 0.075mm, 7%).

[0090] The simulated structure of the NPR anchor cable consists of an NPR cone, Φ1mm stainless steel strand, an NPR casing, a tray and a nut. The NPR cone is made of 304 stainless steel, and the other parts are 3D printed using high-toughness resin materials. According to repeated tests on an electric tensile machine, the constant resistance of the NPR anchor cable simulation structure is approximately 25N. The NPR anchor cable model structure is installed on a 5cm cubic sandstone to form a model structure of the boulder anchor cable structure. In this verification example, the simulated boulder anchor matrix debris flow retaining structure in the flow channel is used as follows Figure 10-11 The 3-2-3 plum blossom matrix is ​​deployed as shown; the control group channel has no blocking structure; Fig.10 As shown, the boulder anchor cable structure is 100mm apart laterally, 400mm apart longitudinally, and the length of the steel strand is 520mm. The constant mass of the debris flow source is 50kg. In order to simulate debris flows exhibiting different flow states, the source mass fractions (mass ratio of particle mass to fluid) are 30%, 40% and 50%, respectively; the control group experimental numbers are: 30%-T, 40%-T, 50%-T; the boulder anchor cable group experimental numbers are: 30%-NB-NPR, 40%-NB-NPR, 50%-NB-NPR. To ensure the flow uniformity of the debris flow source, before opening the source valve 42, a spiral mixer is used to fully stir and ensure that the boulders 31 in the source are in a suspended state, and the dam break release method is adopted, that is, the source valve 42 is opened within 5 seconds. The experimental results are shown in Table 1. Figure 11-12 shown.

[0091] The experimental results show that in the control group, the natural boulders 31 (natural pebbles painted blue or red) arranged before the experiment were transformed into the material source of the debris flow. After the debris flow impact was completed, no particles were deposited in the channel trough.

[0092] like Figure 11-12 The experimental results show that the boulder anchoring matrix effectively intercepts debris flow particles. A large amount of solid sources are intercepted within the boulder anchoring matrix, and the particle deposition behavior shows similarity. As the mass fraction of the source increases, the particle deposition area upstream of the boulder anchoring retaining structure increases. When the mass fraction increases from 30% to 50%, the particle deposition range upstream of the first row of retaining structures increases from 400mm to 1000mm, indicating the sensitivity of the particle deposition effect of the boulder anchoring retaining structure to the mass fraction of the source. It is worth noting that in both experiments, the boulder 31 retaining structure successfully intercepted boulder 31 in the debris flow source, which is of great significance for the protection of the sedimentation area and reducing the impact of the downstream retaining structure. The deposition of the particle source upstream of the retaining structure forms a slope in front of the retaining structure, which reduces the difficulty of the escape of boulder 31 in the source.

[0093] Table 1 Test results of simulated debris flow movement

[0094]

[0095] Fig. 9 P1, P2, P3, P4, P5, and P6 in FIG. 4 are six impact force monitoring points set on the rigid dam body 43. The six monitoring points are arranged on the dam body in two rows and three columns. Fig.12 The comparison of the peak impact force of the control group shows that the peak impact force of the boulder anchor cable experimental group is significantly lower than that of the uncontrolled control group. The peak impact force of the boulder anchor cable experimental group can be reduced by 22% to 96%, with a minimum reduction of 22%. P2 and P6 in the 30%-NB-NPR experiment are slightly larger than P2 and P6 in the control group. The reason is that these two monitoring points are located at the lower part of the left and right sides of the water-facing surface of the rigid dam body 43. When the debris flow source fraction is low, the interception effect of the retaining structure on the solid particles of the debris flow causes the fluid to impact the two sides of the dam body more. Although P2 and P6 in the 30%-NB-NPR experiment are slightly higher than those in the control group, their impact is still far lower than the maximum value of the peak impact force of the dam body.

[0096] From a macroscopic perspective, the boulder anchoring structure controls the movement of the boulder 31 while intercepting particles, resulting in a 35% reduction in the mass of particles impacting the dam body, a significant reduction in the density of the debris flow, and a significant reduction in the impact strength. From the perspective of the internal stress of the debris flow, the boulder anchoring structure increases particle shear and increases the friction between the debris flow and the channel.

[0097] According to the working principle of the present invention and the indoor experimental results of the verification example, it can be known that the present invention can effectively block the debris flow and reduce the scale of the disaster caused by the debris flow to the downstream.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A boulder anchored matrix debris flow barrier structure, characterized in that: It comprises at least three rows of boulder anchor cable structures arranged in a channel in a debris flow flow area, wherein the boulder anchor cable structures are arranged in a plum blossom shape or a rectangular shape in the channel to form a system barrier group; The boulder anchor cable structure includes an anchoring structure fixed in the ditch bed, an NPR anchor cable and a boulder with a size not less than 1.5m×1.5m×1.5m. The NPR anchor cable includes an anchor cable steel strand, an anchor assembly, a constant resistance sleeve and a constant resistance body located in the constant resistance sleeve. The constant resistance sleeve is fixed in the boulder, the first end of the anchor cable steel strand passes through and is fixed in the constant resistance body, and the second end of the anchor cable steel strand is fixed to the anchoring structure through the anchor assembly.

2. The boulder anchoring matrix debris flow barrier structure according to claim 1 is characterized in that: The length of the anchor cable steel strand is greater than 8.0m and less than 30m; the angle between the extension direction of the anchor cable steel strand and the ditch bed is 15° to 30°; the tension load of the anchor cable steel strand is 90% of the tensile strength of the anchor cable.

3. The boulder anchoring matrix debris flow barrier structure according to claim 1 is characterized in that: The anchoring force of the NPR anchor cable is not less than the designed anchoring force of the anchor cable, which is: Where: T k is the anchorage force of the anchor cable, m b is the mass of the boulder, g is the acceleration of gravity, θ is the slope of the ditch bed, μ is the friction coefficient between the ditch bed and the boulder, α d is the debris flow impact correction coefficient, which is generally taken as 1.0~1.5; ρ is the debris flow density, v is the debris flow movement speed, and a and b are the side lengths of the boulder facing the water respectively.

4. The boulder anchoring matrix debris flow barrier structure according to claim 1 is characterized in that: The distance between the boulders and the edge of the channel is not less than 3.0m, the distance between adjacent boulders in the same row is not less than 1.0m and not more than 0.7 times the size of the largest boulder; the distance between two adjacent rows of boulders is 3 to 4 times the average size of the two rows of boulders, and the maximum does not exceed 2.5 times the size of the largest boulder in the two rows.

5. The boulder anchoring matrix debris flow barrier structure according to claim 5 is characterized in that: The anchor cable steel strands are multiple 1×7 unbonded prestressed steel strands, each of which is sheathed with a corrugated tube; all the anchor cable steel strands are passed through a casing, a first end of the casing is fixed in a boulder, an anchor cable isolation bracket is installed at the second end of the casing, some of the anchor cable isolation brackets extend beyond the casing and are installed with casings, and the casing is fixed in an anchoring structure; the middle part of the casing is erected on the bedrock of the ditch bed through a pier.

6. The boulder anchored matrix debris flow barrier structure according to claim 1, characterized in that: The anchoring structure includes an anchor disposed in bedrock of a trench bed.

7. The boulder anchored matrix debris flow barrier structure according to claim 1, characterized in that: The anchoring structure includes an anchor stone, which is a stone existing in the channel with a size of 1.5m×1.5m×1.5m or more. The anchoring assembly is an NPR anchor cable constant resistance structure fixed in the anchor stone, so that the boulder anchor cable structure forms a boulder tension anchor cable structure.

8. The boulder anchoring matrix debris flow barrier structure according to claim 1, characterized in that: The boulder-anchored matrix debris flow retaining structure is arranged in the middle and upper reaches of the main ditch and the middle and lower reaches of the branch ditch in the debris flow flow area; the size range of the boulders is 1.5m×1.5m×1.5m~6m×6m×6m, and the ratio of the sum of the spacing between boulders in the same row to the channel width is 0.4~0.

7.

9. The construction method of the boulder anchor matrix type debris flow barrier structure according to claim 1, characterized in that: The following steps are involved: (1) Design the anchoring structure and boulder location; clean the loose layer in the channel and move the boulder to the predetermined location; calculate the location of the hole in the boulder for installing the constant resistance sleeve, and construct the hole and anchoring structure; (2) Pass the first end of the anchor cable strand through the hole and out of the boulder, install the constant resistance sleeve and constant resistance device in sequence, and then tension the anchor cable strand; (3) When the tension of the anchor cable steel strand reaches the design strength, anchor the first end of the anchor cable steel strand.

10. The construction method of the boulder anchor matrix type debris flow barrier structure according to claim 9, characterized in that: The single anchor cable steel strand is tensioned in stages, with each stage of tensioning load being 0.25, 0.5, 0.75, and 1.2 times the design tension. Each stage needs to be stable for 5 to 10 minutes, and the last stage needs to be stable for 2 to 3 days. When the tension reaches the design strength, the anchor cable is locked. The design tension is 75% of the tensile strength of the anchor cable.

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