A displacement prediction method for landslides with stick-slip characteristics

Abstract

This invention relates to a displacement prediction method for landslides with stick-slip characteristics, comprising the following steps: Step S1: Obtaining calculation parameters of the landslide to be measured; Step S2: Obtaining rainfall intensity, duration, groundwater level, and volumetric water content parameters of the slope surface at the monitoring point of the landslide to be measured; Step S3: Based on the parameters obtained in Steps S1 and S2, calculating the rainwater infiltration of an infinite slope under different rainfall intensities, and calculating the migration depth of the wetting front; Step S4: Establishing the relationship between effective rainfall and groundwater level fluctuations, and calculating pore water pressure; Step S5: Constructing an infinite viscoplastic slope model based on the pore water pressure, and calculating the landslide displacement rate. This invention can provide efficient and high-quality displacement prediction for landslides with stick-slip characteristics.

Description

Technical Field

[0001] This invention relates to the field of geological disaster engineering, specifically to a displacement prediction method for landslides with stick-slip characteristics. Background Technology

[0002] In recent years, landslides and other geological disasters have posed an increasing threat to people's lives, property, and infrastructure. While landslides with stick-slip characteristics may not present direct risk factors, structures on the slope are susceptible to damage from even small displacements. This vulnerability is particularly acute when linear structures experience minute displacements, potentially leading to performance degradation, complete disruption of availability, and even casualties. Therefore, landslide displacement prediction is extremely important. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a displacement prediction method for landslides with stick-slip characteristics, so as to overcome the defects of the prior art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A displacement prediction method for landslides with stick-slip characteristics includes the following steps:

[0006] Step S1: Obtain the soil and rock parameters of the landslide to be tested, including saturated unit weight, friction angle, and cohesion;

[0007] Step S2: Obtain rainfall intensity, duration, groundwater level, and volumetric water content parameters of the slope surface at the monitoring point of the landslide to be tested;

[0008] Step S3: Based on the parameters obtained in Step S1 and Step S2, calculate the rainwater infiltration of an infinite slope under different rainfall intensities, and calculate the migration depth of the moist front.

[0009] Step S4: Establish the relationship between effective rainfall and groundwater level fluctuations, and calculate pore water pressure;

[0010] Step S5: Based on the pore water pressure, construct an infinite viscoplastic slope model and calculate the landslide displacement rate.

[0011] Furthermore, step S3 specifically includes:

[0012] Step S31: Extend the traditional GA model to the slope surface, its expression is:

[0013]

[0014]

[0015] In the formula: f(t) is the infiltration rate at time t; Sf Generalized matrix suction at the moistening front; K s θ is the saturated permeability coefficient; F(t) is the cumulative infiltration rate at time t; θ s θ represents the saturated water content; i α is the initial water content; α is the infinite slope angle; Δθ = θ s -θ i ;

[0016] The generalized matrix suction S at the moistening front f The calculation formula is

[0017]

[0018] In the formula: This is the intake air value; For matrix suction;

[0019] Step S32: Calculate rainfall infiltration based on runoff and rainfall intensity.

[0020] Furthermore, step S32 specifically involves the GA model calculating the relationship between rainfall infiltration and runoff and rainfall intensity, which can be categorized into three cases:

[0021] (1): When the rainfall intensity is less than the infiltration rate during the rainfall interval, but the surface soil layer has not reached saturation, the cumulative infiltration amount is expressed as:

[0022] F(t2)=F(t1)+I p (t2-t1) (4)

[0023] In the formula: I p (t2-t1) represents the rainfall intensity; (t2-t1) represents the rainfall time interval.

[0024] (2): When the rainfall intensity is greater than the infiltration rate during the rainfall interval, and the surface soil layer is saturated, the cumulative infiltration amount is expressed as:

[0025]

[0026] (3): The rainfall intensity is less than the infiltration rate at the beginning of the time interval, and all the rainfall will infiltrate. The surface soil layer changes from an unsaturated state to a saturated state. At this time, the cumulative infiltration amount is as shown in equation (6). p If the situation is consistent with (2), then the cumulative infiltration of rainfall during this time interval is given by equation (8).

[0027]

[0028]

[0029]

[0030] Furthermore, step S4 specifically involves: if N rainfall events with a duration of Δt occur, the relationship between effective rainfall and groundwater level fluctuation is expressed as follows:

[0031]

[0032] In the formula, ΔL is the slope slice of unit width; S r Saturation;

[0033] The pore water pressure is calculated using equation (10), assuming that the groundwater flows parallel to the slope:

[0034] p w =(h(t)+h s )γ w cos 2 α (10)

[0035] In the formula, γ w The specific gravity of water; h s This represents the steady-state groundwater level.

[0036] Furthermore, the momentum balance equation for the infinite viscoplastic slope model is written as follows:

[0037]

[0038] in

[0039]

[0040] In the formula: F v =μv,F v ρ is the viscous force; W is the weight of the infinite slope slice; c is the cohesion of the soil; p w Pore ​​water pressure; denoted as θ, where θ is the internal friction angle of the soil; μ is the viscosity of the soil; v is the slope slip velocity; l is the thickness of the landslide slice; and H(t) is the groundwater level, H(t) = h(t) + h s ;γ s γ is the saturated unit weight of the soil; γ is the natural unit weight of the soil; γ′ is the effective unit weight.

[0041] Assuming that the cohesion, friction, viscosity, and thickness of the shear band remain constant over time, then:

[0042]

[0043] Displacement rate solution using the classic implicit backward difference scheme:

[0044]

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] 1. This invention reproduces the motion evolution process of landslides with stick-slip characteristics under groundwater hydrological response, and can better predict groundwater level changes and landslide displacement rates;

[0047] 2. This invention directly links landslide displacement with rainfall records, using only the expected effective rainfall to predict the landslide's movement rate, which is of great significance for early warning of landslides with stick-slip characteristics. Attached Figure Description

[0048] Figure 1 A flowchart illustrating a displacement prediction method for a landslide with stick-slip characteristics, provided in an embodiment of the present invention;

[0049] Figure 2 A simple viscoplastic model of an infinite slope is provided for embodiments of the present invention;

[0050] Figure 3 Effective rainfall and groundwater level prediction results provided in the embodiments of the present invention;

[0051] Figure 4 The landslide displacement rate prediction results provided in the embodiments of the present invention. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] In this embodiment, a large-scale active landslide in Yaoshan Village, Anxi County, Fujian Province, is used as an example to illustrate the specific implementation process of the present invention. The Yaoshan Village landslide is located approximately 8 kilometers south of Xiping Town, Anxi County, Fujian Province (25.0209°N, 117.9592°E). Figure 1 As shown in the figure, an automated monitoring system was used in the landslide study area. Rain gauges, pore water pressure gauges, inclinometers, and water level gauges were installed at the middle (S1) and lower (S2) of the central axis of the landslide point for real-time, long-term monitoring. Data from each sensor was recorded every hour and transmitted to the monitoring system in real time.

[0054] Please refer to Figure 1 This invention provides a displacement prediction method for landslides with stick-slip characteristics.

[0055] Step S1: Obtain the calculation parameters of the landslide by collecting survey report data or through investigation and laboratory tests;

[0056] Step S2: Based on the rainfall intensity, duration, groundwater level, and volumetric water content parameters of the slope surface obtained from the landslide monitoring points;

[0057] Step S3: Calculate the rainwater infiltration of an infinite slope under different rainfall intensities, and calculate the migration depth of the wetting front;

[0058] Step S4: Establish the relationship between effective rainfall and groundwater level fluctuations, and calculate pore water pressure;

[0059] Step S5: Calculate the landslide displacement rate based on the infinite viscoplastic slope model.

[0060] In this embodiment, the calculation includes the rainwater infiltration of an infinite slope under different rainfall intensities and the calculation of the migration depth of the wetting front.

[0061] Extending the traditional GA model to a slope surface, its expression is:

[0062]

[0063]

[0064] In the formula: f(t) represents the value at time t. t Infiltration rate at time; S f Generalized matrix suction at the moistening front; K s Let F(t) be the saturated permeability coefficient; F(t) is the value at time t. t Cumulative infiltration rate at time; θ s θ represents the saturated water content; i This represents the initial moisture content.

[0065] The generalized matrix suction S at the moistening front f The calculation formula is

[0066]

[0067] In the formula: This is the intake air value.

[0068] The GA model calculates rainfall infiltration and runoff in relation to rainfall intensity, which can be categorized into the following three cases:

[0069] Case 1: The rainfall intensity is less than the infiltration rate during the rainfall interval, but the surface soil layer has not reached saturation. The cumulative infiltration in this case can be expressed as:

[0070] F(t2)=F(t1)+I p (t2-t1) (4)

[0071] Case 2: The rainfall intensity is greater than the infiltration rate during the rainfall interval, and the surface soil layer is saturated. In this case, the cumulative infiltration amount is expressed by the formula.

[0072]

[0073] Case 3: The rainfall intensity is less than the infiltration rate at the beginning of the time interval, so all the rainfall will infiltrate, and the surface soil layer changes from an unsaturated state to a saturated state. The cumulative infiltration at this time is shown in the formula. p Consistent with Case 2, the cumulative infiltration of rainfall during this time interval is given by the formula.

[0074]

[0075]

[0076]

[0077] In this embodiment, the establishment of the relationship between effective rainfall and groundwater level fluctuations, and the calculation of pore water pressure, specifically involves:

[0078] If N rainfall events occur with a duration of Δt, the change in groundwater level can be expressed as:

[0079]

[0080] In the formula, ΔL is the slope slice of unit width; S r This represents saturation.

[0081] Among them, such as Figure 2 The figure shows the calculation results of effective rainfall and groundwater level changes according to the present invention.

[0082] The pore water pressure is calculated from the groundwater level change described in the formula, assuming that the groundwater flows parallel to the slope:

[0083] p w =(h(t)+h s )γ w cos 2 α (10)

[0084] As shown in the figure, the effective rainfall and groundwater level prediction results obtained by GA calculation in this invention are shown.

[0085] In this embodiment, the landslide displacement rate is calculated based on an infinite viscoplastic slope model.

[0086] Among them, such as Figure 1 The figure shows a simple infinite viscoplastic model of the present invention. This infinite viscoplastic model can evaluate the landslide rate affected by groundwater level fluctuations. The movement of the landslide is controlled by a driving force exceeding the Coulomb resistance, which consists of the material's cohesion and friction. This dynamic viscoplastic model can simulate the viscous behavior generated by the forces activated at the beginning of the movement, which increases with velocity.

[0087] For an infinite slope, the momentum balance equation can be written as follows:

[0088]

[0089] in

[0090]

[0091] In the formula: F v =μv,F v ρ is the viscous force; W is the weight of the infinite slope slice; c is the cohesion of the soil; p w Pore ​​water pressure; denoted as θ, where θ is the internal friction angle of the soil; μ is the viscosity of the soil; v is the slope slip velocity; l is the thickness of the landslide slice; and H(t) is the groundwater level, H(t) = h(t) + h s ;γ s γ is the saturated unit weight of the soil; γ is the natural unit weight of the soil; γ′ is the effective unit weight.

[0092] Assuming that the cohesion, friction, viscosity, and thickness of the shear band remain constant over time, the equation can be simplified to:

[0093]

[0094] Solve using the classic implicit backward difference scheme:

[0095]

[0096] Among them, such as Figure 4 The figure shows the landslide displacement rate prediction results of the present invention.

[0097] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for displacement prediction of landslides with stick-slip characteristics, characterized by, The method comprises the following steps: Step S1: obtaining rock-soil parameters of the landslide to be measured; Step S2: obtaining rainfall intensity, duration, groundwater level and volumetric water content parameters of the slope surface of the monitoring point of the landslide to be measured; Step S3: based on the parameters obtained in steps S1 and S2, calculating the rainwater infiltration of the infinite slope under different rainfall intensities, and calculating the migration depth of the wetting front; Step S4: establishing the relationship between effective rainfall and groundwater level fluctuation, and calculating the pore water pressure; Step S5: according to the pore water pressure, constructing an infinite viscoplastic slope model, and calculating the landslide displacement rate; The step S3 is specifically: Step S31: extending the traditional GA model to the slope surface, and its expression is: where: is the infiltration rate at time ; is the generalized matric suction at the wetting front; is the saturated hydraulic conductivity; is the cumulative infiltration at time ; is the saturated water content; is the initial water content; is the infinite slope angle; ; where the generalized matric suction at the wetting front The formula is wherein: is the intake value; is the substrate suction force; Step S32: calculating rainfall infiltration according to runoff and rainfall intensity; The step S32 is specifically: the GA model calculates rainfall infiltration and runoff and rainfall intensity, which is divided into the following three cases: (1): the rainfall intensity is less than the infiltration rate within the rainfall time interval, but the surface soil layer has not reached the saturation state, and the cumulative infiltration amount at this time is represented as: In the formulae: represents the rainfall intensity; represents the rainfall time interval; (2): the rainfall intensity is greater than the infiltration rate within the rainfall time interval, and the surface soil layer is in a saturated state, and the cumulative infiltration amount at this time is represented as: (3): the rainfall intensity is less than the infiltration rate at the beginning of the time interval, all the rainfall will infiltrate, the surface soil layer changes from unsaturated state to saturated state, at this time the cumulative infiltration is shown as formula (6), at time then it is consistent with case (2), then the cumulative infiltration of rainfall in this time interval is shown as formula (8) 。 2. The displacement prediction method of a landslide with stick-slip characteristics according to claim 1, characterized in that, The step S4 is specifically: if a rainfall event occurs with a duration of The effective rainfall and groundwater level fluctuation relationship is expressed as: ​ wherein is a ramp slice of unit width; is a saturation; The pore water pressure is calculated by formula (10), and it is assumed that the groundwater flows parallel to the slope surface: wherein is the specific weight of water; is the steady-state groundwater level.

3. The displacement prediction method of a stick-slip characteristic landslide according to claim 1, wherein The infinite viscoplastic slope model, the momentum balance equation is written as Wherein wherein: , is the viscous force; is the infinite slope slice weight; is the cohesion of the soil; is the pore water pressure; is the internal friction angle of the soil; is the viscosity of the soil; is the slope slip rate; is the landslide slice thickness; is the groundwater level, ; is the saturated density of the soil; is the natural density of the soil; is the effective density; If the cohesion, friction, viscosity and thickness of the shear band remain unchanged over time, then: The classical implicit backward difference format is used to solve the displacement rate: 。

Images