Stability Analysis And Deformation Reinforcement Measures Of Highway Granite Weathered Soil Slope

With the vigorous development of China economy,a large number of highways have been built.In western Guangdong,mountainous hills are the main areas.During the construction of expressways in mountainous areas,excavation and filling of original slopes are inevitable,forming complex cutting slopes and filling embankments.Among them,the granite weathered soil slope composed of fully weathered granite and residual soil is very typical.Due to the engineering characteristics of this type of slope,such as strong weathering,loose structure and strong permeability,the probability of deformation and failure is very high.Especially under the action of excavation and rainfall,it is easy to produce adverse geological disasters such as collapse and landslide,which poses a serious threat to the safety of people’s life and property during the construction and operation period.In this paper,the granite weathered soil slope of Yunmao Expressway is taken as the research object.Through the combination of field investigation,numerical simulation and field monitoring,the main failure modes and influencing factors of granite weathered soil slope are systematically analyzed.The variation law of slope seepage and stability under rainfall is mainly studied,and the deformation mechanism and reinforcement effect of typical granite weathered soil slope are expounded,which provides reference for the stability analysis and deformation reinforcement of granite weathered soil slope.The main research contents and achievements are as follows:(1)Through field investigation and sorting out the data of granite weathered soil slopes of several expressways in Guangdong Province,the main failure modes of granite weathered soil slopes are summarized and analyzed.The main failure modes are arc-like or arc-shaped,broken linear,plane and arc-like composite shapes.The main factors affecting the stability of granite weathered soil slope include slope morphology,rock and soil properties,artificial excavation and rainfall.(2)The numerical simulation method was used to analyze the influence and sensitivity of different influencing factors on slope stability.The slope ratio,cover thickness and slope height ratio were negatively correlated with slope stability coefficient,and slope grade was positively correlated with slope stability coefficient.The contribution value of each influencing factor on the stability coefficient is obtained by orthogonal test method.The sensitivity order is: cohesion > internal friction angle > slope ratio > slope height >slope grade > cover thickness > severe.The shear strength of rock and soil is an important factor affecting the stability of granite weathered soil slope.The stability coefficient estimation formula for granite weathered soil slope is established,which can provide reference for the stability coefficient estimation,analysis and prediction of this type of slope engineering.(3)A typical granite weathered soil slope model was established to study the variation of rock and soil saturation and pore water pressure with time and space and the variation of slope stability coefficient under four rainfall conditions(rainfall intensity,rainfall duration,rainfall type and slope ratio).The increase rate of pore water pressure gradually slowed down until it reached the peak during rainfall,and the decrease rate of pore water pressure gradually decreased after rainfall.slope saturation and pore water pressure increase with the increase of rainfall duration and intensity,the influence of rainfall on shallow rock mass of slope is greater than that on deep rock mass,the slope stability coefficient decreases with the increase of rainfall duration,rainfall intensity and slope ratio during rainfall,and the slope stability gradually recovers after rainfall.The slope displacement increases with rainfall duration and intensity,and the maximum horizontal displacement occurs near the slope toe.When the total rainfall amount and rainfall duration are at the same time,the influence degree of rainfall pattern on the pore water pressure,horizontal displacement and stability coefficient of slope rock and soil mass from large to small is: posterior peak type,uniform type,middle peak type and front peak type.(4)Taking the typical granite weathered soil slope of Yunmao Expressway as the research object,the field monitoring was carried out,and the changes of slope groundwater,slope surface cracking and deformation,and deep displacement after the influence of typhoon "Weipa" continuous rainfall were emphatically analyzed.The potential sliding surface of the slope was about 20m–30m inside the slope,and the displacement of the front edge of the slope was greater than that of the rear edge of the slope,which belonged to the traction failure.The deformation and formation mechanism of granite weathered soil slope were clarified.Taking the slope as the prototype,the deformation and stability changes of the slope excavation and affected by rainfall are simulated.The numerical simulation results are basically consistent with the field monitoring data.The stability coefficient of the slope after deformation is 1.04.In view of the deformation and failure of the slope,the slope deformation reinforcement scheme is proposed,and the reinforcement effect is evaluated.The stability coefficient after reinforcement is 1.71,and the reinforcement scheme has good effect.It provides reference for reinforcement design of similar granite weathered soil slope.