Method for testing influence of loess water content change on slope stability

Abstract

The invention relates to the field of geological engineering and civil engineering, in particular to a method for testing the influence of loess water content change on slope stability. The method comprises the following steps: collecting and preparing a loess sample, measuring physical parameters of the loess sample, and constructing a multi-dimensional physical characteristic matrix of the loess sample; monitoring pore water pressure in real time, and calculating shear stress of the loess sample based on dynamic change data of the pore water pressure; and dynamically updating the dynamic stability parameters of the slope based on the shear stress of the loess sample and the multi-dimensional physical characteristic matrix of the loess sample, and comprehensively evaluating the instability risk of the slope. The problems that a traditional slope monitoring technology lacks systematic research on loess mechanical properties, and consequently the accuracy and reliability of a prediction result are poor are solved; the slope stability is not updated in real time, so that an accurate dynamic monitoring and recursive prediction mechanism cannot be formed; and an early warning signal cannot be timely sent out, so that the landslide emergency response is not timely enough.

Description

Technical Field

[0001] The invention relates to the fields of geological engineering and civil engineering, and in particular to a method for testing the influence of loess water content change on slope stability. Background Art

[0002] Loess is widely distributed in Northwest China, North China and other parts of China. It is a special geological material. Its unique physical and mechanical properties make it highly stable under natural conditions. However, when loess encounters water, its mechanical properties will change significantly. Especially under extreme rainfall conditions, the rapid increase in water content will greatly reduce the shear stress and cohesion of loess, leading to slope instability and landslides. With the increasing frequency of extreme rainfall events caused by climate change, the risk of loess slope landslides is also gradually increasing, posing a serious threat to the safety of surrounding residents and infrastructure. In order to deal with this problem, the engineering field urgently needs a scientific and reliable method to accurately predict and evaluate the stability changes of loess slopes under extreme rainfall conditions, so as to provide an effective early warning means for slope protection.

[0003] The instability mechanism of loess slopes involves complex water-soil interactions. As rainfall infiltrates, water gradually fills the pores of loess, causing an increase in pore water pressure and weakening the shear strength of the soil. At the same time, the depth and rate of water penetration also affect the changes in normal stress and shear stress in the soil, increasing the possibility of slope sliding. Traditional slope stability analysis methods mainly rely on static mechanical property measurements and fail to fully consider the long-term impact of dynamic changes in water content on the mechanical properties of the soil. Although modern slope monitoring technology has made breakthroughs in rainfall, displacement, etc., it is unable to accurately judge the risk of landslides under the combined action of multiple parameters due to the lack of real-time monitoring and analysis of key parameters such as pore water pressure and shear stress.

[0004] The above technology has the following technical problems: lack of systematic research on the mechanical properties of loess under different moisture content and stress conditions, resulting in poor accuracy and reliability of the prediction results; lack of real-time update of the dynamic recursive model for slope stability, resulting in the inability to timely reflect the gradual changes in the mechanical properties of the soil during rainfall, and unable to form an accurate dynamic monitoring and recursive prediction mechanism; unable to issue early warning signals in time when the risk of slope instability is detected, resulting in untimely emergency response to landslides, and sometimes unable to provide sufficient response time for engineering personnel. Summary of the invention

[0005] The present invention provides a testing method for the influence of the change of loess water content on the slope stability, so as to solve the problems that the traditional slope monitoring technology lacks a systematic study on the mechanical properties of loess under different water contents and stress conditions, resulting in poor accuracy and reliability of the prediction results; lacks a dynamic recursive model to update the slope stability in real time, resulting in the inability to timely reflect the gradual changes in the mechanical properties of the soil during rainfall, and unable to form an accurate dynamic monitoring and recursive prediction mechanism; and cannot issue a warning signal in time when the risk of slope instability is detected, resulting in insufficient emergency response to landslides, and sometimes unable to provide sufficient response time for engineering personnel.

[0006] A test method for the influence of loess moisture content change on slope stability of the present invention specifically includes the following technical solutions: A method for testing the influence of loess moisture content change on slope stability comprises the following steps: S1. Collect and prepare loess samples, and measure the physical parameters of the loess samples; construct a multidimensional physical property matrix of the loess samples based on the physical parameters of the loess samples; monitor the pore water pressure in real time to obtain the dynamic change data of the pore water pressure; calculate the shear stress of the loess samples based on the dynamic change data of the pore water pressure; S2. Based on the shear stress of loess samples and the multi-dimensional physical property matrix of loess samples, the dynamic stability parameters of the slope are dynamically updated; based on the dynamic stability parameters of the slope, the instability risk of the slope is comprehensively evaluated to obtain the slope instability judgment value; the slope instability judgment value is used to determine whether the slope has entered an unstable state and quantify the instability situation; when the slope enters an unstable state, the landslide early warning system will sound an alarm and initiate emergency protection measures.

[0007] Preferably, the S1 specifically includes: Based on the physical parameters of loess samples, the mechanical response behavior of loess samples under different moisture content and stress conditions is captured through the multidimensional physical property matrix of loess samples; the specific calculation formula of the multidimensional physical property matrix is: , in, It's time At the time, the loess sample The moisture content condition and Any element in the multidimensional physical property matrix under a stress condition; For time The loess sample Moisture content conditions; is the initial water content of the loess sample; For time Time The density of loess samples under different water contents; It's time At the time, The moisture content condition and Normal stress under stress conditions; It's time At the time, The moisture content condition and Cohesion under stress conditions; For time At the time, The moisture content condition and Friction angle under different stress conditions.

[0008] Preferably, the S1 specifically includes: A rainfall infiltration experiment was carried out on loess samples to measure the changes in pore water pressure inside the loess samples under different rainfall intensities and durations, and to obtain dynamic change data of pore water pressure.

[0009] Preferably, the S1 specifically includes: Based on the dynamic change data of pore water pressure and combined with water content, the shear stress of loess samples is calculated. The specific calculation formula is: , in, For loess samples at time Shear stress at is the initial shear stress; , , , To adjust the parameters; is the water content; It's time The pore water pressure at that time represents the dynamic change data of the pore water pressure.

[0010] Preferably, the S2 specifically includes: Based on the shear stress of loess samples and the multi-dimensional physical property matrix of loess samples, a dynamic recursive model is constructed, and the slope stability recursive formula is introduced to dynamically update the stability parameters of the slope; the slope stability recursive formula is as follows: , in, It's time The stability parameters of the slope when It's time The stability parameters of the slope when For loess samples at time Shear stress at It is cohesion; For time Normal stress at ; is the friction angle; It's time The multidimensional physical property matrix of loess samples; It's time The pore water pressure at the time of , which represents the dynamic change data of pore water pressure; is the water content; is the adjustment coefficient of normal stress.

[0011] Preferably, the S2 specifically includes: In the process of dynamically updating the stability parameters of the slope, the initial state of the loess sample is measured through physical experiments to generate the initial stability parameters of the slope.

[0012] Preferably, the S2 specifically includes: Based on the stability parameters of the slope, combined with the dynamic change data of the shear stress and pore water pressure of the loess samples, the instability judgment formula is introduced to conduct a comprehensive assessment of the instability risk of the slope and obtain the slope instability judgment value; the specific formula is: , in, It's time The slope instability judgment value at this time; is a unit step function, which is used to determine whether the critical condition of landslide is reached. When , it means that the critical condition of landslide is reached and the loess slope is in an unstable state; Used to quantitatively adjust the risk of instability.

[0013] Preferably, the S2 specifically includes: During the physical experiment, the water content of the loess sample will gradually increase, and the pore water pressure and shear stress will be measured in real time. The physical parameters of the loess sample at each stage will be used as the input of the next dynamic recursive model to dynamically update the stability parameters of the slope.

[0014] The beneficial effects of the technical solution of the present invention are: 1. Through detailed experimental research on loess samples, especially the construction of a multidimensional physical property matrix under different water content and stress conditions, the changes in the mechanical properties of loess samples can be fully captured. The multidimensional physical property matrix not only includes basic mechanical parameters such as loess density, porosity, cohesion, friction angle, but also covers dynamic mechanical parameters such as shear stress, normal stress, and pore water pressure. This multidimensional physical data provides a strong foundation for the calculation of the dynamic recursive model, ensuring the comprehensiveness and accuracy of the test data.

[0015] 2. The present invention realizes the dynamic update of the stability parameters of the slope by designing a complex dynamic recursive model and combining the experimental data with the recursive formula of slope stability. The changes in slope stability under different water contents and rainfall conditions can be gradually calculated through the recursive formula of slope stability, forming a real-time dynamic monitoring mechanism. The dynamic recursive model can automatically adjust the stability parameters of the slope according to the real-time monitored physical data, such as pore water pressure, shear stress and normal stress, and accurately predict the instability of the slope.

[0016] 3. The present invention combines the slope stability recursive formula with the instability determination formula, which not only calculates the complex interaction between shear stress and pore water pressure, but also ensures the accuracy of landslide prediction through real-time feedback of mechanical parameters. It can accurately determine whether the slope has entered an unstable state under extreme rainfall conditions; when in an unstable state, the landslide warning system will automatically issue a landslide warning signal, providing efficient landslide risk prompts. Through the instability determination formula, the landslide warning system can accurately evaluate the critical conditions of landslides based on real-time monitoring data, reducing false alarms or missed alarms. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a testing method for the influence of loess moisture content change on slope stability described in the present invention. DETAILED DESCRIPTION

[0018] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0020] The specific scheme of the test method for the influence of the change of loess water content on the slope stability provided by the present invention is described in detail below with reference to the accompanying drawings.

[0021] Refer to the attached Figure 1 , which shows a flow chart of a method for testing the influence of loess moisture content change on slope stability provided by an embodiment of the present invention, the method comprising the following steps: S1. Collect and prepare loess samples, and measure the physical parameters of the loess samples; construct a multidimensional physical property matrix of the loess samples based on the physical parameters of the loess samples; monitor the pore water pressure in real time to obtain the dynamic change data of the pore water pressure; calculate the shear stress of the loess samples based on the dynamic change data of the pore water pressure; Collect loess samples and prepare them to ensure that the water content, density and particle distribution characteristics of the loess samples meet the actual slope conditions. In order to ensure the accuracy of the test data, the water content of the loess samples is gradually controlled under different water content conditions (such as 10%, 15%, 20%, etc.). The physical parameters of the loess samples, such as initial density, porosity, cohesion, friction angle and other key mechanical parameters, are measured through experimental devices, especially the initial water content of the loess samples is accurately measured. The determination of physical parameters not only provides basic data for the subsequent dynamic recursive model, but also ensures that the changes of each physical parameter at different stages can be accurately recorded and transmitted through real-time monitoring of physical sensors (such as soil temperature and humidity sensors, pore water pressure sensors, etc.) in physical experiments, as the initial input conditions of the dynamic recursive model.

[0022] A multidimensional physical property matrix of loess samples is constructed through physical experiments. The multidimensional physical property matrix describes the overall mechanical response behavior of loess samples under different water contents and stress conditions. The specific calculation formula is: , in, It's time At The moisture content condition and Any element of the multidimensional physical property matrix under a stress condition represents the physical state of the loess sample under different water content conditions and stress conditions, reflecting the mechanical properties of the loess sample; For time The loess sample Moisture content conditions; is the initial water content of the loess sample; For time Time The density of loess samples under different water contents is measured based on physical experimental data; It's time At the time, The moisture content condition and Normal stress under a stress condition, wherein the normal stress is the stress acting in a direction perpendicular to the surface of the loess sample; It's time At the time, The moisture content condition and The cohesion under different stress conditions reflects the bonding strength between particles inside the loess sample; For time At the time, The moisture content condition and The friction angle under different stress conditions represents the internal friction characteristics of the loess sample. Through the multi-dimensional physical property matrix of the loess sample, the mechanical change law of the loess sample under different water content conditions is captured, reflecting the influence of cohesion and friction angle on shear stress.

[0023] In the next stage of the experiment, rainfall infiltration experiments were conducted on loess samples to measure the changes in pore water pressure inside the loess samples under different rainfall intensities and durations, and to obtain dynamic change data on pore water pressure. Pore water pressure is a key factor affecting the shear stress of loess samples, so it must be monitored in real time. In rainfall infiltration experiments, rainfall intensity and duration will affect the penetration depth of water in the loess samples, and thus affect the accumulation of pore water pressure.

[0024] The specific calculation formula for the dynamic change data of pore water pressure is as follows: , in, Indicates time The pore water pressure at that time, that is, the dynamic change data of the pore water pressure, represents the pressure generated by water penetrating into the pores of the loess sample; is the unit gravity of water, generally 9.8 kN / m³, and is used to describe the relationship between the weight of water and the depth of water penetration in loess samples; is the water penetration depth that varies with time, indicating the depth of water penetration in the loess sample; is the initial pore water pressure, which indicates the pore water pressure value in the loess sample at the beginning of the experiment; Indicates time The pore water pressure at time ; the integral term It is the cumulative effect of pore water pressure over time. The pore water pressure change law of loess samples under different water contents and rainfall intensities is obtained through the calculation formula of the dynamic change data of pore water pressure. During the experiment, the pore water pressure is measured in real time through the pore water pressure sensor installed in the loess sample, and the dynamic change data of pore water pressure is input into the next calculation process.

[0025] Based on the dynamic change data of pore water pressure, the shear stress of loess samples is calculated. Shear stress directly affects the instability risk of slopes and is an important indicator for predicting slope landslides. According to physical mechanics theory, shear stress is not only affected by normal stress, but also closely related to pore water pressure and water content. The calculation formula for shear stress of loess samples is as follows: , in, For loess samples at time The shear stress at represents the ability of the loess sample to resist shear failure; is the initial shear stress, which represents the shear stress of the loess sample when there is no rainfall; , , , is the adjustment parameter obtained through experimental fitting, which is used to describe the influence of different physical conditions on shear stress; is the water content. The calculation formula of the shear stress of loess samples describes the effect of pore water pressure on shear stress. As the rainfall time gradually increases, the pore water pressure has a weakening effect on the shear stress. As the water content increases, the shear stress is significantly weakened, resulting in a decrease in the shear resistance of the loess samples and a gradual increase in the risk of landslide instability.

[0026] S2. Based on the shear stress of loess samples and the multi-dimensional physical property matrix of loess samples, the dynamic stability parameters of the slope are dynamically updated; based on the dynamic stability parameters of the slope, the instability risk of the slope is comprehensively evaluated to obtain the slope instability judgment value; the slope instability judgment value is used to determine whether the slope has entered an unstable state and quantify the instability situation; when the slope enters an unstable state, the landslide early warning system will sound an alarm and initiate emergency protection measures.

[0027] In order to capture the stability changes of the slope as the water content gradually increases, the calculation results of the shear stress need to be further combined with the normal stress and the friction angle to construct a dynamic recursive model. The dynamic stability of the slope is calculated through the slope stability recursive formula, and the experimental data is combined with the multi-dimensional physical property matrix of the loess sample to dynamically update the stability parameters of the slope. The slope stability recursive formula is as follows: , in, It's time The stability parameter of the slope is used to reflect the current stability of the slope; It's time The stability parameters of the slope when Represents a multidimensional physical property matrix; is the cohesion, measured experimentally; For time Normal stress at ; is the friction angle; is the adjustment coefficient of normal stress. The initial state of loess samples (such as initial water content, initial pore water pressure, initial shear stress, initial normal stress, etc.) is measured through physical experiments to generate the initial slope stability parameters. , the specific formula is as follows: , , in, is the initial shear stress; is the initial normal stress; is the initial pore water pressure; is the unit weight of the loess sample; is the slope height, measured experimentally; is the slope angle, which is determined by experimental design. Through multi-layer recursion, the stability trend of the slope under different water content and rainfall conditions is calculated.

[0028] Based on shear stress and pore water pressure, the instability risk of the slope is comprehensively evaluated, and the instability judgment formula is introduced to obtain the slope instability judgment value. The instability judgment formula is as follows: , in, It's time The slope instability judgment value is used to indicate whether the slope has entered an unstable state and to quantify the instability situation; is a unit step function, which is used to determine whether the critical condition of landslide is reached. When , it means that the critical condition of landslide is reached and the loess slope is in an unstable state; It is used to quantitatively adjust the instability risk and reflect the difference in instability degree; the interaction between pore water pressure and shear stress reflects the dynamic instability trend of the slope under different water content conditions.

[0029] When the slope enters an unstable state, the landslide warning system will sound an alarm. At this time, the operator or the automation system can initiate emergency protection measures, such as strengthening drainage, increasing slope support or evacuating dangerous areas.

[0030] During the physical experiment, the water content of the loess sample is gradually increased through physical permeability experiments, and the real-time pore water pressure and shear stress are measured by physical sensors. The physical parameters of the loess sample at each stage will be directly used as the input of the next step of the dynamic recursive model to ensure the continuity of the data processing between each step and the dynamic changes of the physical parameters. This method of combining physical experiments with dynamic recursive models can accurately simulate the instability process of slopes under extreme rainfall conditions and provide reliable data support for early warning of landslide risks.

[0031] In summary, a test method for the influence of loess moisture content changes on slope stability was completed.

[0032] The order of the embodiments of the invention is for description only and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0033] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A test method for the effect of loess moisture content change on slope stability. It is characterized in that The following steps are involved: S1. Collect and prepare loess samples, and measure the physical parameters of loess samples; Based on the physical parameters of loess samples, a multi-dimensional physical property matrix of loess samples is constructed; pore water pressure is monitored in real time to obtain dynamic change data of pore water pressure; based on the dynamic change data of pore water pressure, the shear stress of loess samples is calculated; S2. Based on the shear stress of loess samples and the multi-dimensional physical property matrix of loess samples, the dynamic stability parameters of the slope are dynamically updated; based on the dynamic stability parameters of the slope, the instability risk of the slope is comprehensively evaluated to obtain the slope instability judgment value; the slope instability judgment value is used to determine whether the slope has entered an unstable state and quantify the instability situation; when the slope enters an unstable state, the landslide early warning system will sound an alarm and initiate emergency protection measures.

2. A method for testing the influence of loess moisture content change on slope stability according to claim 1, It is characterized in that The S1 specifically includes: Based on the physical parameters of loess samples, the mechanical response behavior of loess samples under different moisture content and stress conditions is captured through the multidimensional physical property matrix of loess samples; the specific calculation formula of the multidimensional physical property matrix is: ， in, It's time At The moisture content condition and Any element in the multidimensional physical property matrix under a stress condition; For time The loess sample Moisture content conditions; is the initial water content of the loess sample; For time Time The density of loess samples under different water contents; It's time At the time, The moisture content condition and Normal stress under stress conditions; It's time At the time, The moisture content condition and Cohesion under stress conditions; For time At the time, The moisture content condition and Friction angle under different stress conditions.

3. A method for testing the influence of loess moisture content change on slope stability according to claim 2, It is characterized in that The S1 specifically includes: A rainfall infiltration experiment was carried out on loess samples to measure the changes in pore water pressure inside the loess samples under different rainfall intensities and durations, and to obtain dynamic change data of pore water pressure.

4. A method for testing the influence of loess moisture content change on slope stability according to claim 3, It is characterized in that The S1 specifically includes: Based on the dynamic change data of pore water pressure and combined with water content, the shear stress of loess samples is calculated. The specific calculation formula is: ， in, For loess samples at time Shear stress at is the initial shear stress; , , , To adjust the parameters; is the water content; It's time The pore water pressure at that time represents the dynamic change data of the pore water pressure.

5. A method for testing the influence of loess moisture content change on slope stability according to claim 1, It is characterized in that The S2 specifically includes: Based on the shear stress of loess samples and the multi-dimensional physical property matrix of loess samples, a dynamic recursive model is constructed, and the slope stability recursive formula is introduced to dynamically update the stability parameters of the slope; the slope stability recursive formula is as follows: ， in, It's time The stability parameters of the slope when It's time The stability parameters of the slope when For loess samples at time Shear stress at It is cohesion; For time Normal stress at ; is the friction angle; It's time The multidimensional physical property matrix of loess samples; It's time The pore water pressure at the time of , which represents the dynamic change data of pore water pressure; is the water content; is the adjustment coefficient of normal stress.

6. A method for testing the influence of loess moisture content change on slope stability according to claim 5, It is characterized in that The S2 specifically includes: In the process of dynamically updating the stability parameters of the slope, the initial state of the loess sample is measured through physical experiments to generate the initial stability parameters of the slope.

7. A method for testing the influence of loess moisture content change on slope stability according to claim 5, It is characterized in that The S2 specifically includes: Based on the stability parameters of the slope, combined with the dynamic change data of the shear stress and pore water pressure of the loess samples, the instability judgment formula is introduced to conduct a comprehensive assessment of the instability risk of the slope and obtain the slope instability judgment value; the specific formula is: ， in, It's time The slope instability judgment value at this time; is a unit step function, which is used to determine whether the critical condition of landslide is reached. When , it means that the critical condition of landslide is reached and the loess slope is in an unstable state; Used to quantitatively adjust the risk of instability.

8. A method for testing the influence of loess moisture content change on slope stability according to claim 5, It is characterized in that The S2 specifically includes: During the physical experiment, the water content of the loess sample will gradually increase, and the pore water pressure and shear stress will be measured in real time. The physical parameters of the loess sample at each stage will be used as the input of the next dynamic recursive model to dynamically update the stability parameters of the slope.

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