High-speed remote landslide dynamic process prediction method

Abstract

The invention relates to the technical field of geological disaster prediction, and discloses a high-speed remote landslide dynamic process prediction method, which comprises the following steps: S1, selecting a landslide research area, and obtaining physical and mechanical parameters of solid-phase particles, ice, water, gas, a solid skeleton and a sliding mass of the landslide area; s2, according to the physical and mechanical parameters, establishing a mechanical equilibrium equation, a material conservation equation and an energy conservation equation, and establishing a high-speed remote landslide heat-water-force-steam coupling kinetic model for describing the whole process of ice-water-steam phase change in the cold region; and S3, performing simulation prediction on the dynamic process of the high-speed long-distance landslide through the thermal-water-force-steam coupling dynamic model of the high-speed long-distance landslide to obtain a prediction result. According to the invention, a heat-water-force-steam coupling modeling framework combining solid ice melting and pore water vaporization processes is adopted, the method is suitable for simulating a multi-stage phase change process caused by rapid temperature rise in a landslide shear zone, and transition behaviors among freezing, melting and vaporization stages can be continuously described.

Description

Technical Field

[0001] The present invention relates to the technical field of geological disaster prediction, and in particular to a method for predicting the dynamic process of high-speed and long-distance landslides. Background Art

[0002] The world's cold regions primarily consist of high-latitude permafrost zones, high-altitude glaciers, and perennial snow-covered areas. These regions, covering over 20% of the landmass, are among the most sensitive to environmental change in the context of global warming [see References 1, 2; see references at the end of the background article for a list of references]. According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) [Reference 3], the Arctic region has warmed at a rate of 2 to 3 times the global average over the past 30 years, while the Qinghai-Tibet Plateau has warmed at a rate exceeding 1.5 times the global average. As a result, the cold region's environment is experiencing significant changes, including permafrost degradation, glacier retreat, and increased periglacial landform instability [References 4, 5]. This has led to a significant increase in the frequency and intensity of geological hazards such as landslides, collapses, and debris flows [Reference 6]. Among the many geological hazards in cold regions, high-speed and long-range landslides, due to their suddenness, long travel distances, and significant destructive power, have become a key challenge in disaster prevention and mitigation [Reference 7]. These landslides often exhibit an extremely low equivalent friction coefficient (defined as the ratio of vertical drop to horizontal distance traveled) and travel distances far exceeding those predicted by traditional friction theory, exhibiting a "low friction paradox" [Reference 8]. Because these landslides often occur in alpine snow-covered areas, existing monitoring methods that rely on ground-based sensors or optical remote sensing are unable to efficiently obtain real-time information, posing significant challenges to landslide early warning and management.

[0003] To understand the dynamics of high-speed, long-distance landslides in cold regions, existing research has proposed a variety of theories, including air cushion lubrication, granular debris flow, and frictional heating and drag reduction [References 9-11]. However, most of these theories are based on landslide hazards under normal temperature conditions and lack comprehensive consideration of the ice-water-vapor phase transition within the shear zone of cold-region landslides. Consequently, they struggle to effectively characterize the rapid accumulation of pore pressure and the sharp attenuation of frictional resistance during high-speed sliding.

[0004] Prior art 1:

[0005] Vardoulakis proposed a thermal-hydraulic-mechanical coupled landslide dynamics model based on the mechanism of pore water pressure accumulation caused by frictional heat generation in shear bands [Reference 12]. This model takes the shear band as the research core and combines the three governing equations of mass conservation, energy conservation, and momentum conservation to systematically describe the entire process of temperature rise, hydrothermal expansion, and pore pressure increase caused by frictional heat accumulation during shear. In this model, the shear band is simplified as a one-dimensional thin layer of medium, and the shear deformation is simulated by linear velocity gradient approximation. The evolution of pore water pressure is controlled by the coupling of heat conduction and seepage, and the temperature change is directly related to the shear power dissipation. This model proposed for the first time the feedback path of "frictional heat-hydraulic pressure accumulation-effective stress reduction", providing a quantitative explanation for the long-range characteristics of landslides.

[0006] The shortcomings of prior art 1 are as follows:

[0007] Although the Vardoulakis model lays the theoretical foundation for coupled thermal-hydraulic-mechanical landslide modeling, it is primarily applicable to saturated soil environments under ambient temperature conditions and fails to account for the ice phase component commonly found in shear zones of cold-region landslides. This model fails to account for the latent heat absorption and multiphase structural evolution associated with ice-water phase transitions, leading to deviations in the simulation of shear zone temperature and pore pressure evolution under low-temperature freezing conditions. Furthermore, this model ignores the potential for water vapor conversion processes at elevated temperatures, making it difficult to describe the high-temperature vaporization behavior induced by intense frictional heating during high-speed, long-distance landslides in cold regions.

[0008] Prior art 2:

[0009] He et al. [Ref. 13] introduced the ice-water phase transition mechanism based on the Vardoulakis model and established a coupled thermo-hydraulic-mechanical model suitable for frozen soil landslides in cold regions. This model considers the melting behavior of ice during shear zone temperature rise and uses a temperature-driven saturation relationship to describe the transition from ice-dominated to water-dominated pore structure. Furthermore, the model incorporates a latent heat term due to the ice-water phase transition to modify the temperature field distribution, thereby more accurately characterizing the shear zone heat balance and its influence on pore pressure evolution. This approach significantly improves the simulation accuracy of frozen soil landslides during the initiation and acceleration phases, and can preliminarily reflect the coupled mechanism of "thermal-induced phase transition, pore pressure response, and flow enhancement" in frozen soil landslides.

[0010] The shortcomings of the second prior art are as follows:

[0011] While He et al.'s model considers the ice-water phase transition process, expanding the applicability of traditional models to cold-region landslides, it still fails to account for the phase transition behavior of water vapor under high-temperature conditions. Furthermore, the model fails to fully account for the dynamic effects of temperature strain and plastic deformation on the effective stress of the soil, making it difficult to accurately reflect the true mechanical response of the shear zone.

[0012] Prior art three:

[0013] Zhao Nenghao et al. [Reference 14] proposed a coupled thermal-hydraulic-mechanical-vapor dynamic model of landslides that considers the water vapor phase transition process, addressing the potential high-temperature water vapor phase transition phenomenon within shear zones of high-speed landslides. Building on the traditional three-field coupling framework, this model further incorporates gas phase components to construct the water-vapor two-phase mass conservation and Darcy flow governing equations. Parameters such as the latent heat of water vapor phase transition, vapor saturation, gas density, and dynamic viscosity are incorporated into the energy equations and pore pressure evolution expressions. This model is able to describe the localized vaporization behavior caused by frictional heating in shear zones and its enhanced effect on pore pressure and sliding response, preliminarily revealing the nonlinear evolutionary path of "shear heating-pore water vaporization-pore pressure jump-slip acceleration."

[0014] The shortcomings of prior art three are as follows:

[0015] Although Zhao et al.'s model considers high-temperature vaporization effects, it does not yet couple the ice-water phase transition process. In actual high-speed landslides in cold regions, shear zones often undergo a dynamic evolution from a mixed ice-water-vapor state, with the phase transition characterized by both staged and continuous processes. Therefore, modeling the ice-water-vapor three-phase process separately may result in an incomplete depiction of the transition zone.

[0016] References:

[0017] [1]Gruber S.Derivation and analysis of a high-resolution estimate ofglobal permafrost zonation[J].The Cryosphere,2012,6(1):221-233.

[0018] [2]Shen H.Colde Regions Science and Marine Technology[M].EolssPublishers Company Limited Oxford,UK,2015.

[0019] [3]IPCC.Summary For Policymakers[M] / / Masson-Delmotte V,Zhai P,PiraniA,et al.Cambridge,United Kingdom and New York,NY,USA:Cambridge UniversityPress,2021:3-32.

[0020] [4] Gao Yang, Li Bin, Feng Zhen, et al. Analysis of global climate change and geological disaster response [J]. Journal of Geomechanics, 2017, 23(01): 65-77.

[0021] [5] Lu Jianying, Yu Guoan, Huang Heqing. Research and prospects on the formation mechanism of debris flow in high mountainous areas under the influence of climate change [J]. Journal of Glaciology and Geocryology, 2021, 43(02): 555-567.

[0022] [6] Yang Qingqing, Zheng Xinyu, Su Zhiman, et al. Research progress on high-speed and long-range ice-rock debris flows[J]. Earth Science, 2022, 47(3): 935-949.

[0023] [7] Wang Yufeng, Lin Qiwen, Li Kun, et al. Research progress on dynamics of high-speed long-distance landslides[J]. Journal of Earth Sciences and Environment, 2021, 43(01): 164-181.

[0024] [8]Heim A.Bergsturz und menschenleben[M].Fretz&Wasmuth,1932.

[0025] [9]Shreve R L.Leakage and fluidization in air-layer lubricatedavalanches[J].Geological Society of America Bulletin,1968,79(5):653-658.

[0026]

[10] Davies TR H.Spreading of rock avalanche debris by mechanicalfluidization[J].Rock Mechanics,1982,15(1):9-24.

[0027]

[11] Voight B,Faust C. Frictional heat and strength loss in some rapidlandslides[J].Geotechnique,1982,32(1):43-54.

[0028]

[12] Vardoulakis I.Dynamic thermo-poro-mechanical analysis ofcatastrophic landslides[J].Geotechnique,2002,52(3):157-171.

[0029]

[13] He C, Liu E, He S, et al. On the supraglacial rock avalanches: Thermo-hydro-mechanical analysis considering ice-water phase transition [J]. Geomorphology, 2023, 422: 108550.

[0030]

[14] Zhao Nenghao. Research on high-speed landslide dynamics model based on shear band friction-heat generation-pressurization and engineering application[D]. China University of Geosciences, 2019. Summary of the Invention

[0031] In order to overcome or alleviate one or more of the above technical problems, the purpose of the present invention is to provide a method for predicting the dynamic process of high-speed long-distance landslides. This prediction method is based on the frictional heating effect of the shear band and takes into account the entire ice-water-vapor phase transition process, and establishes a thermal-hydraulic-mechanical-vapor coupled dynamic model of high-speed long-distance landslides in cold regions. Based on the influence of frictional heating on shear band temperature and water pressure, this model further describes the evolution of pore pressure caused by the phase transition process and its feedback mechanism on effective stress and sliding friction, thereby effectively simulating the initiation and movement process of high-speed long-distance landslides in cold region freeze-thaw environments. This model can provide a theoretical basis and technical support for landslide disaster prediction, risk assessment, and prevention and control design.

[0032] The present invention provides the following technical solutions:

[0033] A method for predicting the dynamic process of high-speed long-distance landslides comprises the following steps:

[0034] S1: Select a landslide area for study and obtain the physical and mechanical parameters of solid particles, ice, water, gas, solid skeleton, and sliding body in the landslide area;

[0035] S2: Based on the physical and mechanical parameters, a high-speed, long-distance landslide thermal-hydraulic-mechanical-vapor coupled dynamic model is constructed to describe the entire process of ice-water-vapor phase transition in cold regions by establishing mechanical equilibrium, material conservation, and energy conservation equations; the mechanical equilibrium equations include the sliding body mechanical equilibrium equation and the shear band mechanical equilibrium equation; the material conservation equations include the liquid phase material conservation equation and the gas phase material conservation equation; the energy conservation equation includes calculating the equivalent thermodynamic parameters of the three-phase mixture of rock and soil when the shear band is below and above 0°C, respectively, and establishing energy conservation equations at different temperatures during the plastic deformation heat release process in the shear band during the sliding of the sliding body;

[0036] S3: The high-speed long-distance landslide dynamic process is simulated and predicted by the high-speed long-distance landslide thermal-hydraulic-mechanical-steam coupled dynamic model to obtain a prediction result.

[0037] Further, the step S2 includes the following steps:

[0038] S21: Establishing the sliding body mechanical equilibrium equation in the landslide area

[0039] According to Newton's second law, the motion equation of the sliding body is expressed as:

[0040]

[0041] Where ρ is the density of the sliding body, D is the thickness of the sliding body, v is the speed of the sliding body along the slope, t is the time of landslide movement, g is the acceleration of gravity, β is the inclination angle of the sliding surface, τ h is the shear stress within the shear band;

[0042] Shear stress τ h is generated by the friction effect between the sliding body and the substrate, and its expression is

[0043]

[0044] Among them, μ C is the coefficient of friction of the sliding surface, defined as μ C =tanδ, δ is the landslide friction angle, σ' is the normal stress in the shear zone, p = χ L p L +(1-χ L )p C is the average pore pressure, χ L is the liquid water saturation, p L and p C are pore water pressure and pore ice pressure respectively;

[0045] Substituting Equation (2) into Equation (1) and dividing by the thickness per unit mass ρD, the final form of the sliding body motion equation is obtained:

[0046]

[0047] S22: Establishing the shear band mechanical equilibrium equation

[0048] When the shear band temperature is less than or equal to 0°C, the momentum conservation equation is:

[0049]

[0050] Where σ represents the total stress tensor, φ is the porosity, ρs, ρ L , ρ Crepresents the density of solid particles, water, and ice, respectively. According to the pre-thaw dynamics theory, there is some unfrozen water below the freezing point in frozen soil, that is, supercooled water. The porous ice cannot form a continuous skeleton to bear the shear stress. Therefore, the effective stress principle of the ideal frozen soil three-phase continuous medium proposed by Bishop is adopted, that is:

[0051]

[0052] Where α = 1-K d / K S represents the Biot coefficient, K d represents the bulk modulus of the frozen soil skeleton, K S represents the stiffness of soil particles, δ ij represents the Kronecker function, which is 1 when i=j and 0 when i≠j;

[0053] When the shear band temperature is greater than 0°C, the momentum conservation equation is:

[0054]

[0055] Where, ρ V Indicates gas density;

[0056] Bishop's effective stress principle also applies to the coexistence of water vapor:

[0057]

[0058] Where p V represents the pore pressure;

[0059] S23: Establishing the liquid phase substance conservation equation

[0060] When the shear zone temperature is less than or equal to 0°C, since liquid water and pore ice exist in the pores at the same time, the overall governing equation for the changes in pore water pressure and pore ice pressure under small deformation conditions is obtained based on the conservation of state equation for liquid phase matter:

[0061]

[0062] Among them, p L 、p C represent pore water pressure and pore ice pressure respectively, K L , K C are the bulk moduli of liquid water and solid ice, S cryo It represents the low-temperature suction caused by the surface tension of ice / water in frozen soil and is defined as S cryo =max(p C -p L ,0),β S , β L , β Care the thermal expansion coefficients of solid particles, liquid water, and ice particles, respectively. θ is the temperature of the frozen soil in the shear zone. v LS represents the velocity of the liquid phase relative to the solid phase, ε v is the volume strain of the shear band;

[0063] When the shear band temperature is greater than 0°C, the following pore water pressure governing equation is obtained by considering the small strain assumption:

[0064]

[0065] Where S represents matrix suction, which is defined as S = p V -p L ;m L→V represents the rate of water vapor phase change;

[0066] S24: Establishing the gas phase conservation equation

[0067] According to the gas phase conservation equation and the state equation, the pore pressure control equation under small deformation conditions is obtained as follows:

[0068]

[0069] Where K V is the bulk modulus of the gas, K V ≈p V β V is the thermal expansion coefficient of water vapor, defined as β V =1 / θ; v VS It represents the velocity of the gas phase relative to the solid phase;

[0070] S25: Establish the energy conservation equation

[0071] Assuming that the shear zone is in a state of local thermal equilibrium, that is, the temperatures of the solid, liquid and gas phases are equal, and considering that the permeability of the shear zone is extremely low and the landslide movement time is short, the contribution of thermal convection to heat transport is negligible. Therefore, the energy conservation equation of the shear zone without considering the thermal convection term is:

[0072]

[0073] Where ρ is the density of the mixed material in the frozen soil, C p and λ m represents the specific heat capacity and thermal conductivity of the mixture, Q is the heat source term;

[0074] When the shear zone temperature is lower than or equal to 0℃, the equivalent thermodynamic parameters of the three-phase mixture of rock and soil are expressed as:

[0075]

[0076] Where C S , CL , C C and λ S ,λ L ,λ C are the specific heat capacity and thermal conductivity of the solid, liquid and ice phases respectively;

[0077] When the shear zone temperature is greater than 0℃, the equivalent thermodynamic parameters of the three-phase mixture of rock and soil are

[0078]

[0079] Where C V and λ V are the heat capacity and thermal conductivity of the gas phase respectively;

[0080] During the sliding process of the sliding body, the plastic deformation in the shear zone will lead to energy dissipation. The plastic deformation includes shear deformation and volume deformation, most of which is released in the form of frictional heat, thereby significantly increasing the shear zone temperature. As the temperature rises, the pore ice in the permafrost shear zone will begin to undergo a phase change, that is, solid ice melts into liquid water. This phase change process will absorb a large amount of latent heat and thus offset part of the temperature rise caused by frictional heat. When the shear zone temperature rises to a certain level, the liquid water in the pores will undergo a water vapor phase change reaction, which is also accompanied by heat absorption. Therefore, the heat source term in the energy conservation equation at different temperatures is composed of two parts: phase change heat and plastic power dissipation. Its expression is:

[0081]

[0082] in, is the plastic volume strain rate, d is the thickness of the shear band; L LC L is the latent heat of ice-water phase change, which represents the heat released by unit mass of water during the freezing process, usually about 333.5kJ / kg; LV It represents the latent heat of water vapor phase change, that is, the heat absorbed by unit mass of water when it changes from liquid to gas. Its value is affected by temperature and is expressed as:

[0083] L LV =2.501×10 6 -2369.2θ (15).

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] (1) This paper proposes a thermal-hydraulic-mechanical-vapor coupled modeling framework that uniformly considers the melting of solid ice and the vaporization of pore water. This framework is suitable for simulating the multi-stage phase transition process caused by the rapid temperature increase in the landslide shear zone and can continuously describe the transition behavior between the freezing, melting, and vaporization stages.

[0086] (2) This paper establishes a model of the landslide drag reduction mechanism driven by shear band frictional heat generation, clarifies the impact path of temperature change on pore pressure evolution, and regulates the energy conservation process through the latent heat of ice-water-vapor phase transition, effectively reflecting the coupling mechanism between the pore pressure accumulation rate and the acceleration response of the sliding body;

[0087] (3) The present invention effectively compensates for the shortcomings of existing technologies in characterizing low-temperature freezing and high-temperature vaporization by constructing a high-speed, long-distance landslide thermal-hydraulic-mechanical-vapor coupled dynamic model that considers the entire ice-water-vapor phase transition process. Compared with previous models that can only describe ice-water phase transition or water vapor phase transition, the present invention can continuously capture the dynamic process of pore water in the sliding body melting from a frozen state and further vaporizing based on the shear band friction heat generation theory, thereby more accurately reflecting the rapid accumulation of pore pressure and the nonlinear attenuation behavior of sliding friction resistance. In the landslide dynamic evolution analysis, the model significantly improves the ability to capture the high-temperature pressure mechanism in the shear band, and can more realistically reproduce the suddenness and remoteness characteristics of cold-region landslides. In addition, the present invention has achieved numerical solution in a multi-physics field simulation platform and can be directly used for process simulation, disaster-causing capacity assessment and risk control analysis of landslide disasters, with good engineering applicability and promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 A schematic diagram of the evolution of motion characteristic parameters of a landslide during the acceleration phase provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0089] The present invention is described in detail below with reference to the embodiments and accompanying drawings. However, it should be understood that the embodiments and accompanying drawings are merely exemplary descriptions of the present invention and do not constitute any limitation on the scope of protection of the present invention. All reasonable variations and combinations within the scope of the inventive concept of the present invention fall within the scope of protection of the present invention.

[0090] To implement the high-speed remote landslide dynamics prediction method proposed in the present invention, the following implementation steps are carried out in combination with actual landslide areas:

[0091] The landslide area selected in this embodiment is located in a certain place in the Himalayas of India. It is a typical high-altitude cold area with significant initial high drop, long-range accumulation characteristics and obvious thermal disturbance phenomenon. The slope morphology, rock and soil structure and thermophysical properties of the landslide area are obtained through remote sensing image analysis (such as Sentinel-2, Landsat-8), on-site geological surveys and geophysical data. The surface morphology and initial temperature distribution of the sliding body are obtained by means of unmanned aerial vehicle laser scanning (UAV-LiDAR) and thermal infrared aerial survey (TIR), and the thermodynamic and mechanical parameters of solid skeletons, ice, water, gas and other media in the stratum are obtained by combining borehole tests and laboratory tests. The above data are used as an important source of model input parameters, and are gridded and pre-processed by interpolation and filtering methods to ensure the accuracy of model calculations.

[0092] This example utilizes the COMSOL Multiphysics multi-physics simulation platform, building a modular computational architecture based on the thermal-hydraulic-mechanical-steam coupled governing equations of the present invention. An unstructured mesh (tetrahedron) is used within the computational domain, and the shear band region is densified to capture phase transition behavior in high-gradient regions. A coupled solver is employed to address nonlinear terms and strong coupling. Boundary conditions include a constant temperature at the upper boundary of the sliding body, an adiabatic lower boundary, velocity continuity in the shear band, and a frozen hydrostatic pressure field as the initial state.

[0093] To validate the applicability and effectiveness of the coupled thermal-hydraulic-mechanical-vapor dynamics model for high-speed, long-distance landslides constructed in this paper, a landslide event occurring in India was selected as a representative case study, and the motion of the sliding mass during the acceleration phase was numerically simulated. This landslide, located in the Himalayan high-altitude frozen region, exhibits typical characteristics of a high initial drop, a long movement path, and long-distance accumulation. The landslide was accompanied by significant signs of thermal damage and vaporization of sliding zone material, consistent with the characteristics of the landslide type targeted by the present model.

[0094] In this example, the landslide mass was simplified to a rectangular block structure. The sliding surface inclination was set to 33° based on remote sensing interpretation and field data. The sliding mass thickness was set to 80m, and the shear zone thickness was set to 0.05m. The initial model temperature was -8°C, and the boundary conditions were set to a constant temperature at the upper boundary of the sliding mass and an adiabatic boundary at the lower boundary. The upper and lower surfaces of the shear zone met the velocity continuity condition, and the initial pore water pressure was the hydrostatic pressure distribution under the frozen stable state. Table 1 lists the basic physical and mechanical parameters used in the calculation of this landslide model.

[0095] Table 1 Calculation parameters of landslide model

[0096]

[0097] Figure 1Shows the evolution results of the motion characteristic parameters of the landslide from instability to the collision point at the bottom of the valley, including the temperature of the shear zone, the increment of pore water pressure, the liquid water saturation, the pore ice pressure, the pore air pressure value, the frictional resistance of the sliding surface, and the variation trends of the landslide body's movement speed and displacement with time. The solid line represents the results calculated using the landslide dynamics model considering high-temperature vaporization, while the dashed line represents the results calculated using the model without considering high-temperature vaporization.

[0098] When considering the phenomenon of high-temperature vaporization, according to the state change of the pore substances in the shear zone ( Figure 1 (c)), the movement process of the landslide body can be divided into three stages. The first stage is the ice-water phase change stage (t ≤ 3.5 s): When the landslide becomes unstable and starts to slide, the temperature in the shear zone will increase due to frictional heat generation. At the same time, the pore ice in the frozen soil melts into liquid water due to heat. However, because the ice-water phase change process requires heat absorption, the temperature rise in the early shear zone is relatively slow ( Figure 1 (a)), and thus it cannot cause an obvious hydrothermal pressurization effect. Meanwhile, because the melting of solid ice will cause the pore ice pressure to rapidly decrease ( Figure 1 (d)), the average pore pressure value will gradually decrease during the ice-water phase change process, and the effective normal stress in the vertical direction of the sliding surface increases. This leads to a continuous increase in the frictional resistance on the sliding surface ( Figure 1 (e)), and thus slows down the acceleration of the landslide body in the initial stage of movement. Therefore, the landslide body slides downward at a relatively low speed in the early stage ( Figure 1 (f)).

[0099] The second stage is the liquid water saturation stage (3.5 s < t < 21 s): When the pore ice completely melts into liquid water, the temperature in the shear zone further accelerates to increase under the continuous frictional heat generation ( Figure 1 (a)), and thus induces a stronger hydrothermal pressurization effect ( Figure 1 (b)). Therefore, the frictional resistance of the sliding surface begins to decrease sharply, thus significantly promoting the growth of the landslide body's movement speed ( Figure 1 (f)).

[0100] The third stage is the high-temperature vaporization stage (t ≥ 21 s): With the continuous enhancement of frictional heat generation, the temperature in the shear zone rises sharply, which induces the high-temperature vaporization reaction of liquid water, resulting in a gradual increase in the pore air pressure. At the same time, the high temperature also causes a stronger hydrothermal pressurization effect. Therefore, the combined growth of air pressure and water pressure makes the pore pressure increase significantly, and the frictional resistance of the sliding surface will further rapidly decrease and gradually approach zero ( Figure 1 (e)). Finally, the movement speed of the landslide body shows a faster growth trend.

[0101] From Figure 1It can be seen that during the ice-water phase transition stage, the evolution of the landslide characteristic parameters calculated by the two models is basically the same. However, as the shear zone temperature continues to rise, the generation of pore gas pressure leads to a significant increase in the average pore pressure compared to the case without considering high-temperature vaporization, which in turn reduces the effective normal stress on the sliding surface. Therefore, the friction resistance encountered by the sliding body during movement is relatively lower ( Figure 1 (e)). Although the smaller friction resistance will weaken the frictional heating effect of the shear band, the sliding body has a higher speed growth rate ( Figure 1 (f)), so the shear band temperature rises faster when considering high temperature vaporization ( Figure 1 (a)), which makes the hydrothermal pressurization rate relatively larger ( Figure 1 (b)). However, since the high-temperature vaporization process of liquid water is accompanied by phase change and heat absorption, the final shear band temperature rise is slightly lower than that without considering high-temperature vaporization ( Figure 1 (a)). Figure 1 As can be seen from (e) and (f), the accumulation of pore gas pressure causes the frictional resistance of the sliding body to drop rapidly to near zero in a shorter time, thereby allowing the sliding body to enter the "resistance-free high-speed sliding" stage earlier. As a result, the time it takes for the sliding body to reach the valley bottom collision point is significantly shortened, from 65 seconds when high-temperature vaporization is not considered to 56 seconds. At the same time, the maximum movement speed increases from 87 m / s to 105 m / s.

[0102] This indicates that the high-temperature vaporization effect significantly enhances the sliding mass's mobility and destructive potential by further weakening the frictional resistance of the sliding surface. This suggests that water vapor phase transition plays a crucial role in landslide dynamics, with a significant impact on landslide acceleration, displacement, and ultimate damage. Therefore, incorporating water vapor phase transition effects into landslide dynamics models can improve the theoretical framework for describing the dynamics of high-speed, long-range landslides, thereby furthering our understanding of landslide catastrophic mechanisms and ultimately providing a reliable theoretical foundation and technical support for the prediction, prevention, and control of catastrophic landslides in cold regions.

[0103] Based on the above simulation process, this example extracts the sliding body's displacement-time curve, velocity changes, shear zone temperature, pore pressure, and phase evolution images, and visualizes the distribution of multi-physics field parameters in a three-dimensional model. Combined with dynamic indicators such as the sliding body's arrival velocity, acceleration, and terminal position, this can be used to determine whether the landslide is likely to reach the designated valley bottom and cause secondary disasters. By comparing the output of a model that does not consider vaporization, the degree of influence of phase change mechanisms on the landslide evolution path is clarified, providing a scientific basis for early landslide warning.

[0104] The landslide prediction system constructed based on this method can be further integrated with regional meteorological models, earthquake triggering models, and high-resolution remote sensing monitoring platforms to form a landslide risk assessment system applicable to complex geological environments in cold regions. The model's pre-assessment capabilities can assist local governments in optimizing disaster emergency response plans, implementing classified management and resource allocation in landslide-prone areas, and improving the scientific and timely nature of disaster prevention and control.

[0105] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A method for predicting the dynamic process of high-speed and long-distance landslides, characterized by: The following steps are involved: S1: Select a landslide area for study and obtain the physical and mechanical parameters of solid particles, ice, water, gas, solid skeleton, and sliding body in the landslide area; S2: Based on the physical and mechanical parameters, a thermo-hydraulic-mechanical-vapor coupled dynamic model of a high-speed, long-distance landslide is constructed to describe the entire process of ice-water-vapor phase change in cold regions by establishing mechanical equilibrium, material conservation, and energy conservation equations; the mechanical equilibrium equations include a sliding body mechanical equilibrium equation and a shear band mechanical equilibrium equation; the material conservation equations include a liquid phase material conservation equation and a gas phase material conservation equation; the energy conservation equation includes an energy conservation equation that considers heat conduction, ice-water vapor phase change latent heat, plastic energy dissipation, and shear band frictional heat generation during the sliding process of the sliding body when the shear band is below and above 0°C, respectively; S3: The high-speed long-distance landslide dynamic process is simulated and predicted by the high-speed long-distance landslide thermal-hydraulic-mechanical-steam coupled dynamic model to obtain a prediction result.

2. The method for predicting the dynamic process of high-speed long-distance landslide according to claim 1 is characterized in that: The step S2 comprises the following steps: S21: Establishing the sliding body mechanical equilibrium equation in the landslide area According to Newton's second law, the motion equation of the sliding body is expressed as: Where ρ is the density of the sliding body, D is the thickness of the sliding body, v is the speed of the sliding body along the slope, t is the time of landslide movement, g is the acceleration of gravity, β is the inclination angle of the sliding surface, τ h is the shear stress within the shear band; Shear stress τ h is generated by the friction effect between the sliding body and the substrate, and its expression is Among them, μ C is the coefficient of friction of the sliding surface, defined as μ C =tanδ, δ is the landslide friction angle, σ' is the normal stress in the shear zone, p = χ L p L +(1-χ L )p C is the average pore pressure, χ L is the liquid water saturation, p L and p C are pore water pressure and pore ice pressure respectively; Substituting Equation (2) into Equation (1) and dividing by the thickness per unit mass ρD, the final form of the sliding body motion equation is obtained: S22: Establishing the shear band mechanical equilibrium equation When the shear band temperature is less than or equal to 0°C, the momentum conservation equation is: Where σ represents the total stress tensor, φ is the porosity, ρs, ρ L , ρ C represents the density of solid particles, water, and ice, respectively. According to the pre-thaw dynamics theory, there is some unfrozen water below the freezing point in frozen soil, that is, supercooled water. The porous ice cannot form a continuous skeleton to bear the shear stress. Therefore, the effective stress principle of the ideal frozen soil three-phase continuous medium proposed by Bishop is adopted, that is: Where α = 1-K d / K S represents the Biot coefficient, K d represents the bulk modulus of the frozen soil skeleton, K S represents the stiffness of soil particles, δ ij represents the Kronecker function, which is 1 when i=j and 0 when i≠j; When the shear band temperature is greater than 0°C, the momentum conservation equation is: Where, ρ V Indicates gas density; Bishop's effective stress principle also applies to the coexistence of water vapor: Where p V represents the pore pressure; S23: Establishing the liquid phase substance conservation equation When the shear zone temperature is less than or equal to 0°C, since liquid water and pore ice exist in the pores at the same time, the overall governing equation for the changes in pore water pressure and pore ice pressure under small deformation conditions is obtained based on the conservation of state equation for liquid phase matter: Among them, p L 、p C represent pore water pressure and pore ice pressure respectively, K L , K C are the bulk moduli of liquid water and solid ice, S cryo It represents the low-temperature suction caused by the surface tension of ice / water in frozen soil and is defined as S cryo =max(p C -p L ,0),β S , β L , β C are the thermal expansion coefficients of solid particles, liquid water, and ice particles, respectively. θ is the temperature of the frozen soil in the shear zone. v LS represents the velocity of the liquid phase relative to the solid phase, ε v is the volume strain of the shear band; When the shear band temperature is greater than 0°C, the following pore water pressure governing equation is obtained by considering the small strain assumption: Where S represents matrix suction, which is defined as S = p V -p L ;m L→V represents the rate of water vapor phase change; S24: Establishing the gas phase conservation equation According to the gas phase conservation equation and the state equation, the pore pressure control equation under small deformation conditions is obtained as follows: Where K V is the bulk modulus of the gas, K V ≈p V β V is the thermal expansion coefficient of water vapor, defined as β V =1 / θ; v VS It represents the velocity of the gas phase relative to the solid phase; S25: Establish the energy conservation equation Assuming that the shear zone is in a state of local thermal equilibrium, that is, the temperatures of the solid, liquid and gas phases are equal, and considering that the permeability of the shear zone is extremely low and the landslide movement time is short, the contribution of thermal convection to heat transport is negligible. Therefore, the energy conservation equation of the shear zone without considering the thermal convection term is: Where ρ is the density of the mixed material in the frozen soil, C p and λ m represents the specific heat capacity and thermal conductivity of the mixture, Q is the heat source term; When the shear zone temperature is lower than or equal to 0℃, the equivalent thermodynamic parameters of the three-phase mixture of rock and soil are expressed as: Where C S , C L , C C and λ S ,λ L ,λ C are the specific heat capacity and thermal conductivity of the solid, liquid and ice phases respectively; When the shear zone temperature is greater than 0℃, the equivalent thermodynamic parameters of the three-phase mixture of rock and soil are Where C V and λ V are the heat capacity and thermal conductivity of the gas phase respectively; During the sliding process of the sliding body, the plastic deformation in the shear zone will lead to energy dissipation. The plastic deformation includes shear deformation and volume deformation, most of which is released in the form of frictional heat, thereby significantly increasing the shear zone temperature. As the temperature rises, the pore ice in the permafrost shear zone will begin to undergo a phase change, that is, solid ice melts into liquid water. This phase change process will absorb a large amount of latent heat and thus offset part of the temperature rise caused by frictional heat. When the shear zone temperature rises to a certain level, the liquid water in the pores will undergo a water vapor phase change reaction, which is also accompanied by heat absorption. Therefore, the heat source term in the energy conservation equation at different temperatures is composed of two parts: phase change heat and plastic power dissipation. Its expression is: in, is the plastic volume strain rate, d is the thickness of the shear band; L LC L is the latent heat of ice-water phase change, which represents the heat released by unit mass of water during the freezing process, usually about 333.5kJ / kg; LV It represents the latent heat of water vapor phase change, that is, the heat absorbed by unit mass of water when it changes from liquid to gas. Its value is affected by temperature and is expressed as: L LV =2.501×10 6 -2369.2θ (15).

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