Method for stabilizing moving avalanche and landslide covers on complex terrain

Abstract

FIELD: construction; engineering protection of territories; environmental management.SUBSTANCE: invention relates to the construction, engineering protection of territories and environmental management of avalanche-prone slopes, as well as from landslides, rocks, etc. The method for stabilizing moving avalanche and landslide covers on complex terrain includes the installation of a support structure, which consists of posts and power anchor piles, as well as retaining nets placed up and down the slope. Retaining barriers are installed in rows across the potential avalanche or landslide, which contain retaining nets in the form of a triangular cable-stayed structure made of steel cables, one of which is placed with its horizontal side on the surface of the slope and the tip upwards, and the other with its tip installed on the slope and the horizontal side upwards, these nets are alternately secured with bolted connections to each other and to supports in the form of steel tubular racks, which are located at the base of the slope. The support structure has additional anchors installed up and down the slope, and steel cables to connect these anchors to the steel tubular posts. To ensure the distribution of load transfer on the terrain surface, a foundation block with a socket for a hinged connection with them, as well as with power anchor piles, is installed under each tubular post, and the distance between the tubular posts and the step between the rows of retaining barriers are set depending on the thickness of the mobile slope cover in the exit zone and the slip coefficient, ensuring adaptability to complex terrain and variable loads.EFFECT: increasing the efficiency and reliability of protecting territories and linear objects from moving avalanches and landslides due to stabilization in the zone of their potential descent, and also significantly reducing the material and labour intensity of installation work.1 cl, 4 dwg

Description

[0001] The invention relates to construction, engineering protection of territories and environmental protection of avalanche-prone slopes, as well as protection from landslides, rocks, etc.

[0002] A method of protection against snow avalanches is known, comprising an avalanche cutter itself, made in the form of a triangular structure in plan, consisting of two side walls mounted on a frame and forming a cutting edge with an angle, L, wherein the avalanche cutter is installed on the surface of the snow cover in the period preceding the predicted time of the avalanche, cutting and diverting the avalanche flow from the protected object and at least one anchor, securing the avalanche cutter with a cable in a stable position on the surface of the snow cover, wherein the device is made of some durable material, for example, composite, metal, etc., in the form of collapsible movable structures assembled from individual elements (blocks) (SU No. 2462550 C1, IPC E01F7 / 00, 2011). However, this method of protecting slopes from snow avalanches involves installing a barrier in the path of an already moving avalanche to cut it and divert it, rather than prevent it.

[0003] A method for retaining snow and landslides is known, which includes installing a rigid frame on which a main mesh and an additional, finer mesh are fixed, wherein the frame of the mesh panel is a supporting steel frame, made in the form of a trapezoid and provided with fastening elements symmetrically located relative to the horizontal and vertical axis of the panel, in order to be able to connect the panels together in a row, wherein the main mesh is made of intersecting reinforcing bars, and the additional mesh is made flexible and is a fine-mesh double-twisted wire connected to a layer of mesh geotextile, jointly fixed on a support cable stretched over the supporting steel frame, located along the perimeter of the panel (RU No. 174847 U1, IPC E01F 7 / 04, E01 F 7 / 04, 2017).

[0004] The disadvantage of this invention for snow and landslide detention is that the rigid frame of the panel is not able to adapt to complex, uneven terrain, requiring labor-intensive adjustment or slope planning, and the design does not have a built-in mechanism for dynamic load distribution, therefore, the rigid transfer of forces to the anchors can lead to local overloads and damage.

[0005] The closest in technical essence to the proposed invention is the technical solution set out in patent RU No. 90453 U1, IPC E01F7 / 04, 2008., the essence of which is a method for preventing snow avalanches, including the installation of posts and anchors made of metal pipes, as well as a mesh filling secured with its lower slope edge to the upper ends of the posts, with its upper slope edge laid on the ground and secured to it, characterized in that the mesh filling is made of individual flat rectangular mesh elements, and the upper ends of the posts and anchors are provided with diametrical grooves for mechanical fastening of the mesh filling, also when installing terraces in rows across the slope, the upper slope edges of the meshes are secured to the ground at the upper ends of the anchors, and on all posts and anchors, except for the outermost ones in the row, the edges of two adjacent meshes are simultaneously secured, and when installing terraces in rows along the slope, the upper slope edge of the mesh is secured to the ground by the bases of the posts of the above-located tier of the terrace, and the upper edge of the mesh of the highest tier along the slope is secured to the upper ends of the anchors.

[0006] The disadvantage of this method is that without hinge joints and flexible elements, the structure is vulnerable to ground movement and sudden loads, which increases the risk of damage to the supports. Installation of the system also requires significant labor costs and special slope preparation, and the lack of modularity complicates transportation and assembly in hard-to-reach areas.

[0007] The technical result of the proposed invention is an increase in the efficiency and reliability of protecting territories and linear objects from moving avalanches and landslides due to stabilization in the zone of their potential descent, as well as a significant reduction in the material intensity and labor intensity of installation work compared to traditional methods aimed at stopping an already moving avalanche and landslide.

[0008] The technical result is achieved in that in the method for stabilizing the moving covers of an avalanche and a landslide on a complex terrain, including the installation of a support structure, which consists of racks and power anchor piles, as well as retaining nets placed up and down the slope, characterized in that the retaining barriers are installed in rows across the potential descent of an avalanche or landslide and contain retaining nets in the form of a triangular cable-stayed structure made of steel cables, one of which is placed with the horizontal side on the surface of the slope and the tip upward, and the other - with the tip installed on the slope and the horizontal side upward, these nets are alternately secured with bolted connections to each other and to supports in the form of steel tubular racks, which are located at the base of the slope, and the support structure has additional anchors installed up and down the slope and steel cables for connecting these anchors with steel tubular racks,In this case, to ensure the distribution of load transfer on the surface of the terrain, a foundation block with a socket for a hinged connection with them, as well as with power anchor piles, is installed under each tubular post, and the distance between the tubular posts and the step between the rows of retaining barriers are set depending on the thickness of the mobile slope cover in the exit zone and the slip coefficient, ensuring adaptability to complex terrain and variable loads.

[0009] A comparative analysis showed that the claimed method, in comparison with the prototype, ensures the stability of the layer of mobile cover in the zone of a potential avalanche, thereby preventing the launch of the avalanche itself, rather than weakening its impact, and at the same time reduces the material and labor intensity of installation on complex terrain.

[0010] The novelty of the claimed method lies in the creation of a flexible and durable barrier that effectively distributes the load over its area and adapts to the unevenness of the slope and provides the maximum opportunity to prevent the initiation of an avalanche with minimal material consumption and complexity of installation of the structure, which is modular, easily transported and assembled.

[0011] According to the patent and technical literature, no technical solution similar to the claimed one has been found, which allows us to judge the inventive level of the proposed landslide prevention system.

[0012] The essence of the invention is explained by the drawing, where Fig. 1 is a plan of the arrangement of retaining barriers, Fig. 2 is a section profile A-A, Fig. 3 is a typical diagram of the device of retaining barriers, side view, Fig. 4 is a typical diagram of the device of retaining barriers, top view.

[0013] The method for stabilizing moving avalanche and landslide covers on complex terrain is implemented using a system that includes retaining barriers 1 consisting of retaining nets 2, which are the main retaining element, which are attached to supports made in the form of steel tubular posts 3 (Fig. 3). Power anchor piles 4, which perceive vertical loads from the tubular steel post 3 and horizontal loads from the system of cables 6 (Figs. 2, 3). Retaining barriers 1 are installed in rows. Retaining nets 2 have the form of triangular cable-stayed structures made of steel cables installed alternately, one of which is placed with the horizontal side on the slope surface and the tip upward, and the other is installed with the tip on the slope and the horizontal side upward (Figs. 3, 4). In Fig. 3 grids 2 are secured with bolted connections (not shown in the figure) between themselves and with steel tubular posts 3, which are located at the base of the slope.The supporting structure has additional anchors 5 installed up and down the slope and steel cables 6 for connecting these anchors 5 with steel tubular posts 3. In order to ensure the distribution of load transfer on the surface of the terrain, a foundation block 7 with a socket (not shown in the Fig.) for tubular posts 3 is installed under each tubular post 3, which are installed vertically with the ability to change the angle of inclination. The distance between the tubular posts 3 and the step between the rows of retaining barriers 1 are set depending on the thickness of the mobile slope cover in the exit zone and the slip coefficient, ensuring adaptability to complex terrain and variable loads. Rows of retaining barriers 1 are installed in the avalanche origin center 8, retaining structures 9 in the form of walls on a pile foundation, which are intended to strengthen the slope and prevent landslides, are located along the designed highway 10 (Fig. 1).To protect metal elements (anchors) from corrosion, polyethylene pipes 11 are used (Fig. 3).

[0014] The claimed method is implemented as follows: first, the construction site is thoroughly prepared, including clearing trees and grading the ground while preserving the natural topsoil. Following this, the anchor piles 4 are marked and installed. They are placed upslope along the perimeter of the future retaining barrier 1 at intervals of 3.5-4.0 m, determined by the thickness of the movable cover and the slip coefficient. Boreholes are drilled for the anchor piles to the design depth, then reinforcement cages made of class AIII (A400) rebar are installed, and concreting is performed using the vertically moving pipe method. Concrete of class B25 with W6 water resistance and F200 frost resistance grades is used. In parallel with the installation of the power piles 4, additional anchors 5 are installed, placing them fan-shaped up and down the slope from the future position of the tubular steel posts 3.Special attention is given to additional anchors 5 installed downslope, as they bear the main thrust load. Foundation blocks 7 are installed on the finished load-bearing piles 4, fixing the position of the tubular support posts 3 and ensuring uniform load transfer into the soil base. Installation of the supports begins with the installation of steel tubular posts 3. They are secured to the foundation blocks 7 via articulated ball joints in the block sockets (not shown in the figure), which allows the system to deform under uneven shear loads. Steel tubular posts 3 are aligned vertically, taking into account the slope angle of up to 40°. Retaining meshes 2 of the triangular cable-stayed structure are alternately installed between posts 3 at intervals of 3.5-4.0 m. The first mesh is laid with the horizontal side on the ground and the acute angle upwards; the next one is installed in an inverted position, with the acute angle in the ground. The grids 2 are connected to each other by bolted connections (not shown in the figure).To ensure spatial rigidity, a cable stabilization system is installed, comprising 6 galvanized steel cables. The 6 steel cables connect the upper portions of the struts 3 to the additional upper and lower anchors 5. All cable connections are made using thimbles and KP-1M clamps. After all components are installed, the tension of the 6 cables is adjusted using turnbuckles, monitoring the force with a torque wrench. The final step is to backfill the sinuses with local soil and compact them layer by layer, and a two-layer waterproofing coating is applied to all concrete surfaces in contact with the ground. The completed retention barrier is a flexible modular system capable of effectively withstanding the dynamic loads of snow loads and preventing avalanches in their potential initiation zone.

[0015] An example of a specific implementation of the claimed method

[0016] To confirm the effectiveness of the proposed method, a pilot section of the highway in the Ober Khutor area, the "Daphne" section, was selected. The design site is located on the northern slopes of the Aibga ridge at altitudes of 860-1300 m. Geologically, up to 38 m, grusty-blocky soils with sandy loam-loamy filler predominate (III complexity category according to GOST 25100-2020). Seasonally variable groundwater levels are noted. The climate is humid, the average annual precipitation is 1974 mm (maximum up to 188 mm / day), which provokes erosion. Seismicity is 8 points (MSK-64), 8.2 points are taken for calculations. Landslides are actively developing (with a volume of up to 10,000 m 3), linear erosion, and flooding. The slope stability assessment results show that the stability coefficient for the basic load combination is 0.981 (according to the Shakhunyants method) and 1.080 (according to the Bishop method), while for a special load combination taking into account seismic impact of 8 points, it decreases to 0.958 and 0.997, respectively, which is below the standard value of 1.21, confirming the need for stabilization measures. The physical and mechanical properties of the soils, determined during laboratory tests, include the angle of internal friction from 24° to 32°, cohesion from 8 to 32 kPa, deformation modulus from 15 to 41 MPa, as well as moisture, density, and porosity indicators, which are taken into account when modeling the structure's performance.The soil's corrosiveness to metal elements (including steel cables and anchors) is assessed as predominantly moderate, necessitating special protective measures such as galvanizing the cables and using polyethylene pipes to insulate the anchors. These initial data form the basis for calculating the parameters of the adaptive retaining system, including the selection of element types and geometry, installation spacing, anchorage depth, and material requirements. The core of the system consists of 1200 mm diameter bored anchor piles, placed in two rows at 2500 mm intervals along the slope. The piles are 24 meters long, ensuring their embedment in stable soils below potential sliding surfaces.The piles are made of B25 grade concrete with standardized water resistance and frost resistance properties and are reinforced with spatial frames: longitudinal reinforcement of class A500C makes up 3% of the pile's cross-sectional area, while transverse reinforcement of 14 mm diameter stirrups spaced 90 mm apart provides shear force absorption. A monolithic reinforced concrete grillage (similar to the foundation block in the patent) is installed on top of the piles, 1200 mm high and 4500 mm wide, which serves to unite the piles into a single frame and uniformly distribute the loads. The grillage is reinforced in the tension zone with five 32 mm diameter bars of class A500C, laid according to the standard "Type 8" scheme. On a grillage with a variable pitch, determined by calculations for local loads, steel tubular posts (supports of retaining barriers) are installed, which are connected to the foundation block through hinge joints, which allows them to adaptively deflect under uneven soil pressure.Retaining barriers are installed directly on the slope. They consist of triangular cable-stayed structures made of galvanized steel cables, which are alternately attached to tubular posts. One mesh is laid with its base facing the slope, and the other with its inverted base facing upward, forming an intersecting load-bearing grid. The mesh elements are connected and secured to the posts using bolts with controlled tightening force. The system is stabilized in the longitudinal and transverse directions by a system of prestressed cables that connect the upper portions of the posts to additional anchors installed up and down the slope. The anchors are type 103 / 43 with a borehole diameter of 175 mm and a length of 21 to 39 meters, depending on their position in the section. Their minimum estimated material load-bearing capacity is 2150 kN.The anchor installation spacing is set at 2,500 mm, and their inclination angle to the horizontal is 30 degrees, which optimizes the pull-out performance. To protect against corrosion, all metal components, including anchor tie rods and connections, are encased in polyethylene pipes, and exposed concrete surfaces are coated with a waterproofing material. System parameters, such as the spacing between posts, pile reinforcement density, and the length and number of anchors, are determined using numerical modeling in the Plaxis software package, taking into account variability in soil conditions and dynamic loads. This ensures the structure's adaptability to local terrain features and time-varying impacts.

[0017] Ensuring the reliability and durability of the system is based on a set of design checks carried out in accordance with the requirements of SP 381.1325800.2018, SP 63.13330.2018, and other regulatory documents. Primary priority is the verification of the overall slope stability, for which the calculated stability coefficient kst is defined as the ratio of the sums of the restraining and shear moments or forces along the critical sliding surface, calculated using the finite element method in the Plaxis software package. For a specific combination of loads, taking into account seismic impact, the obtained values ​​are kst = 0.958 (using the Shakhunyants method) and kst = 0.997 (using the Bishop method). These values ​​are compared with the normalized coefficient [kst], defined as [kst] = γn ψ / γd, where γn = 1.15 is the reliability coefficient for normal-level structures, ψ = 0.95 is the load combination coefficient for a special combination, γd = 0.9 is the operating conditions coefficient. Thus, [kst] = 1.15 · 0.95 / 0.9 ≈ 1.21. Since the condition kst ≤ [kst] is met, the need for the designed retaining structure to bring the stability margin to the standard level is confirmed. The strength of reinforced concrete elements (piles, grillage, retaining wall) is checked based on the condition ψ · F ≤ γd · R / γn, where F is the calculated force (longitudinal force, bending moment, shear force) obtained from the Plaxis model, and R is the bearing capacity of the section established in accordance with SP 63.13330.2018 depending on the section geometry, concrete class B25 and reinforcement characteristics A500C. For bored piles with a diameter of 1200 mm with a reinforcement percentage of 3%, a check is performed for the combined action of the longitudinal force and bending moment, confirming sufficient bearing capacity. The load-bearing capacity of anchor devices for the rod material is checked based on the condition Na ≤ Rs · As, where Rs is the calculated resistance of the anchor steel, As is its cross-sectional area.For type 103 / 43 anchors used in the system, the accepted minimum required bearing capacity is 2150 kN. A simultaneous check of the anchor's pull-out bearing capacity in soil is performed, taking into account the shear resistance along the cylindrical surface in the soil and the resistance under the anchor's heel. Seismic effects are taken into account by introducing into the calculation an additional horizontal ground acceleration ah, determined by the formula ah = K1 Ko A. For site conditions with a design seismicity of 8 points, the following is adopted: coefficient K1 = 0.5 (accounts for permissible damage to the retaining structure), coefficient Ko = 1.1 (accounts for the normal level of responsibility), parameter A = 2.0 m / s. 2 . Thus, ah = 0.5·1.1·2.0 = 1.1 m / s 2In the Plaxis model, this acceleration is specified by the dimensionless coefficient kh = ah / g = 1.1 / 10 = 0.11, which is applied to the entire calculated soil mass and structures. All calculations are performed for two main load combinations: the primary load (self-weight, live load from traffic) and the secondary load (with added seismic impact), which ensures the system's performance is verified both under operating conditions and under rare extreme events. The calculation results confirm that the adopted design parameters of the system (geometry, spacing, reinforcement) ensure the fulfillment of all strength, stability, and deformability conditions, laying the foundation for its adaptability to real-world variable loads and complex terrain.

Claims

A method for stabilizing the moving covers of an avalanche and a landslide on a complex terrain, including the installation of a support structure, which consists of racks and power anchor piles, as well as retaining nets placed up and down the slope, characterized in that retaining barriers are installed in rows across the potential avalanche or landslide, which contain retaining nets in the form of a triangular cable-stayed structure made of steel cables, one of which is placed with the horizontal side on the surface of the slope and the tip upward, and the other with the tip installed on the slope and the horizontal side upward, these nets are alternately secured with bolted connections to each other and to supports in the form of steel tubular racks, which are located at the base of the slope, and the support structure has additional anchors installed up and down the slope, and steel cables for connecting these anchors to the steel tubular racks,In this case, to ensure the distribution of load transfer on the surface of the terrain, a foundation block with a socket for a hinged connection with them, as well as with power anchor piles, is installed under each tubular post, and the distance between the tubular posts and the step between the rows of retaining barriers are set depending on the thickness of the mobile slope cover in the exit zone and the slip coefficient, ensuring adaptability to complex terrain and variable loads.

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