CN109506606B - Linear speed reciprocal method for predicting slope critical slip time - Google Patents

Abstract

The invention discloses a linear speed reciprocal method for predicting the critical slip time of a side slope, which comprises the following steps: 1. selecting a concrete landslide body to be predicted, calculating the displacement speed of the side slope, and making a speed reciprocal-time scatter diagram in an accelerated sliding stage; 2. the formula of the invention is used for fitting the speed reciprocal-time scatter diagram to obtain the predicted slope critical slip time. The invention has the advantages that: the calculation of the critical sliding time has definite physical significance, and the invention can provide more accurate prediction.

Description

Linear speed reciprocal method for predicting slope critical slip time

Technical Field

The invention belongs to the technical field of geological disaster prevention and control, and particularly relates to a linear velocity reciprocal method for predicting slope critical slip time.

Background

China is a multi-mountain country, the mountain area accounts for 2/3 of the land area of the country, the mountain area is complex in geological structure and fragile in ecological environment, mountain disasters frequently burst, and the loss caused by the mountain disasters accounts for one fourth of the total loss caused by various natural disasters. Landslide is a common geological disaster, and monitoring and early warning of the landslide are core tasks of disaster prevention and control work. Therefore, the method has great practical significance for predicting the landslide occurrence time in advance through the corresponding monitoring technology.

At present, the common landslide monitoring method is based on the monitoring of the surface displacement of the side slope, and the critical slide time of the side slope is predicted through a corresponding critical slide criterion. The speed reciprocal method is a prediction method which is widely applied and is relatively simple at present. The calculation formula of the speed reciprocal method is as follows:

wherein A is an empirical constant, t_fFor landslide time, t_*To accelerate the monitoring of the destruction phase, v_*Is given as_*The corresponding displacement speed.

In practical application, the speed of an accelerated sliding stage is obtained through displacement monitoring data calculation, and a speed reciprocal-time scatter diagram is drawn; then, assuming that the inverse velocity of the temporary slip is 0, the temporary slip time t is predicted by using the intersection point of the fitted curve of the inverse velocity-time scatter diagram and the time axis_f。

According to the characteristics of the speed reciprocal-time curve in the accelerated sliding stage, landslides can be mainly divided into two types: 1. the straight line type is shown in FIG. 1, and the curve of the reciprocal velocity-time scatter point is a clear straight line; 2. the asymptotic profile is shown in FIG. 2, in which the divergence point of the velocity-time curve is an asymptote approaching the time axis.

This method has the following problems: 1. the physical meaning of the intersection point of the speed reciprocal-time curve and the time axis is not clear; 2. for a slope with a speed reciprocal-time scatter diagram of a gradual type, because a fitting curve does not have an intersection point with a time axis, the method cannot directly give the slide time of the slope, and needs to be specified through experience, so that the prediction error is large.

Disclosure of Invention

The invention aims to provide a linear speed reciprocal method for predicting the critical slip time of a side slope, which can enable the calculation of the critical slip time to have clear physical significance and can improve the prediction accuracy of the linear type slope.

The technical problem to be solved by the invention is realized by the technical scheme, which comprises the following steps:

step 1, selecting a concrete landslide body to be predicted, calculating original displacement monitoring data of the landslide body in an accelerated sliding stage to obtain the speed of a corresponding monitoring moment, and making a speed reciprocal-time scatter diagram in the accelerated stage;

if the scatter points are asymptotic towards the time axis in the reciprocal velocity-time plane, then the velocity is dynamically long averaged, or dynamically short averaged:

taking dynamic short average when n is 3 and dynamic long average when n is 7;

and 2, fitting the speed reciprocal-time diagram, wherein the fitting formula is as follows:

in the formula, t_*To speed up the monitoring moment of the destruction phase, v_*Is given as_*Corresponding displacement speed, t₀Is a certain moment v of the initial stage of the slope accelerated sliding₀Is t₀Sliding rate of time, t_fThe critical slip time;

step 3, fitting the speed reciprocal-time scatter diagram obtained in the step 1 by using the formula in the step 2 to obtain the temporary slip time t_f。

The invention has the technical effects that:

compared with the conventional speed reciprocal method, the method can directly obtain the critical slip time t through a fitting formula of speed reciprocal-time relation when predicting the critical slip time of the side slope_fThe physical significance is more definite, and the prediction precision is high.

Drawings

The drawings of the invention are illustrated as follows:

FIG. 1 is a velocity-time diagram for a straight-line landslide;

FIG. 2 is a speed-time diagram of an asymptotic landslide;

FIG. 3 is a velocity reciprocal-time scatter plot of an embodiment;

FIG. 4 is a plot of inverse velocity versus time after the raw velocity dynamic long average process.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

in this embodiment, a Stromboli landslide is selected, and the following steps are performed:

step 1, selecting a concrete landslide body to be predicted, calculating original displacement monitoring data of the landslide body in an accelerated sliding stage to obtain the speed of a corresponding monitoring moment, and making a speed inverse-time scatter diagram in the accelerated stage according to a calculation formula of a speed inverse method; FIG. 3 is a velocity reciprocal-time scattergram of the present example.

If the scatter points are distributed asymptotically towards the time axis in the velocity reciprocal-time diagram, the velocity can be processed by a previous data processing, such as dynamic long average (LMA) or dynamic short average (SMA):

the patent takes the dynamic short average when n is 3 and the dynamic long average when n is 7; obtaining a linear distribution velocity reciprocal-time graph after the treatment; the velocity inverse-time graph after the velocity of fig. 3 is subjected to the dynamic long average processing is shown in fig. 4.

Step 2, fitting the speed reciprocal-time scatter point after the dynamic long average treatment to obtain a specific expression, and solving the critical slip time t_f；

The empirical formula of speed and acceleration in accelerated creep phase of a landslide proposed by "Fukuzono T (1985) A new method for predicting the failure time of slopes, proceedings,4th International Conference & Field works on landslopes, Tokyo, pp 145-150" ("Fukuzono T (1985) slope failure time prediction, fourth International society for landslide Conference, Tokyo, Page number 145-150"):

v^-α*a＝A (2)

in the formula (2), v is the velocity of the slope, a is the acceleration of the slope, and α and a are empirical constants.

The rate at which the formula (2) is integrated is expressed as follows (α > 1):

in the formula, v_fRate of landslide instability, t_fThe critical slip time.

Let t be t at any time during the accelerated destruction phase_*，ν＝v_*Converting the formula (3) to obtain:

assuming the speed v at which a landslide is temporarily slippery_fWhen α is 2, formula (4) reduces to:

let t₀Is a certain moment v of the initial stage of the slope accelerated sliding₀For the sliding rate at this time, there are:

from a comparison of equation (5) with equation (6) at both ends, we obtain:

fitting the velocity reciprocal-time scatter diagram obtained in the step 1 by using the formula (7) to obtain the critical slip time t_f；

When the scatter points are linearly distributed in the reciprocal velocity-time diagram, that is, α is 2, the scatter points can be directly fitted to the scatter diagram according to the formula (7) by using a tool such as MATALAB, so as to obtain the predicted critical slip time t_f。

Δt＝t_*-t₀For monitoring the time t_*And t₀The time interval in between.

The temporary slip time t calculated by the invention_f201.5 hours differs from the actual landslide time of 205 hours by only 3.5 hours.

In order to further verify the prediction accuracy of the method, the temporary slip time of eight landslides is calculated through the steps and is compared with the real landslide time, and the specific calculation result is shown in a table 1:

TABLE 1

Name of landslide	Real landslide time/day	Predicting the critical slip time/day
			Switch station for terrace	527	525
Temple with sleeping dragon	66	67
			Chicken temple	466	463
White mountain Bierdanggu (Japan)	113	112
			Huang Zz	544	540
La Chenaula	884	886
			Benishan	258	258
Selburn	600	599

As can be seen from table 1: the difference between the predicted critical sliding time and the real sliding time is very small, and the predicted critical sliding time of some cases is the same as the real sliding time. Therefore, the method can be used for predicting the landslide time in actual engineering, so that the life and property loss caused by landslide is reduced to the maximum extent.

Claims (1)

1. A linear speed reciprocal method for predicting the critical slip time of a side slope is characterized by comprising the following steps:

step 1, selecting a concrete landslide body to be predicted, calculating original displacement monitoring data of the landslide body in an accelerated sliding stage to obtain the speed of a corresponding monitoring moment, and making a speed reciprocal-time scatter diagram in the accelerated stage; if the scatter points are distributed in the reciprocal velocity-time plane in a manner of gradually approaching to the time axis, the velocity is subjected to dynamic long average or dynamic short average:

taking dynamic short average when n is 3 and dynamic long average when n is 7;

and 2, fitting the speed reciprocal-time diagram, wherein the fitting formula is as follows:

in the formula, t_*To speed up the monitoring moment of the destruction phase, v_*Is given as_*Corresponding displacement speed, t₀Is a certain moment v of the initial stage of the slope accelerated sliding₀Is t₀Sliding rate of time, t_fThe critical slip time;

step 3, fitting the speed reciprocal-time scatter diagram obtained in the step 1 by using the formula in the step 2 to obtain the temporary slip time t_f。

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