Instability Mechanism And Pre-control Measures Of Cut Slope In Red Bed Soft Rocks With Gentle Dip Angle

Red beds are widely distributed in my country,especially in the southwest and central regions.With the increasing construction of water conservancy,transportation and other projects,there are many cases of instability in mountainous areas and red-bed slopes of reservoir banks.According to statistics of 80 cases of red-bed landslides in the southwestern region,it is found that the dip angle of the rock with the largest number of landslides is mainly concentrated between 15° and 25°,which is a gently dipping bedding failure.Therefore,it is of great significance to understand the instability mechanism of the soft rock cut slope of the gently dipping bedding red bed and take corresponding pre-control measures for disaster prevention and mitigation.In view of this,this article is based on field investigation and theoretical analysis,combined with indoor physical model tests and numerical analysis,to carry out the study of the instability mechanism and pre-control measures of the soft rock slope in gentle red beds.The specific research work and results are as follows:(1)Through on-site investigation and theoretical research,the structural types of gently-dipping red bed slopes are divided,the deformation and failure modes of the gently-dipping red bed slopes are summarized,and the main controlling factors of instability(including the geometric characteristics of the slope,the stratigraphic rock)are summarized.Characteristics,structural surface characteristics,cutting slope excavation,rainfall and earthquakes,etc.),and deduced the corresponding calculation formula for the slip range of the loose zone under the cutting slope of the gentle bedding slope.(2)Through physical model tests,the failure mode,displacement and deformation laws and stress adjustment characteristics of the gently-dipping bedding slope under hierarchical cutting slope unloading are revealed.The results show that the failure mode of the slope body after cutting the slope is a typical pull-slip failure;the deformation of the slope body is mainly composed of two parts: the unloading deformation in the cutting stage and the creep deformation in the standing stage;the internal stress of the slope changes with the cut The slope process is constantly adjusted,and the overall trend is downward.(3)Through numerical analysis,the influence law of rock inclination,thickness and cut slope ratio on the stability of gently dipping bedding red bed slopes is discussed.The results show that the greater the bedding angle,the lower the stability of the slope;the greater the thickness of the rock layer,the lower the stability of the slope;the smaller the cut slope ratio,the higher the stability of the slope.(4)Through the orthogonal design method,the sensitivity of the slope angle,the thickness of the rock layer and the slope ratio of the cut slope to the slope stability is analyzed,and the horizontal combination scheme of the most unfavorable factors is analyzed.The results show that the primary and secondary sensitivity of the factors is cut slope ratio> bedding angle> rock layer thickness;the horizontal combination scheme of factors that is most unfavorable to slope stability is bedding angle 20°,rock layer thickness 2m,and cut slope ratio 1:0.5.(5)The pre-control performance of ordinary anti-slide piles and pressure-relief anti-slide piles are compared and studied.The results show that the slope stability coefficient is 1.47 without supporting measures;after ordinary anti-slide piles,the slope stability coefficient increases from 1.47 to 1.74;after the pressure-type anti-slide piles are supported,the slope is stable The coefficient of performance increased to 1.78,indicating that the compression-type anti-slide piles have good pre-control performance,and under the same safety support premise,the size of the compression-type anti-slide piles is smaller,which can reduce the engineering reinforcement cost.