Analysis On Influence Of Dry-wet Cycle Effect On Slope Stability For Low Liquid Limit Clay Embankment In Operating Mountainous Expressway

Aiming at the problem of the slope instability of the operating mountainous expressway caused by the atmospheric dry-wet cycle,taking the low liquid limit clay embankment slope at K86+850 of S42 Huangshan to Qimen Expressway in Anhui Province as the research object,through the simulated.experiment of dry-wet cycle and numerical simulation of slope seepage field and its stability,analyzing the influence of dry-wet cycle and rainfall on the slopes stability of the soil embankment to guide the maintenance and prevention of slopes.(1)Direct shear tests of soil samples with 3 kinds of initial moisture content and 3 kinds of dry density composite states under 6 kinds of dry-wet cycle conditions show that the effect of dry-wet cycle will reduce the shear strength of soil samples,and the attenuation amplitude after the first dry-wet cycle is the largest,and then gradually decreases.In the case of a certain moisture content or dry density,soil samples with a larger dry density or moisture content have a stronger ability to resist the effect of dry-wet cycle.Based on this,the relationship model of shear strength and its parameters with dry density,moisture content and the times of the dry-wet cycle is established..(2)The soil-water characteristic curve of the soil sample fitted by the VG model shows that with the increase of the times of dry-wet cycle,the soil-water characteristic curve gradually moves down,indicating that the dry-wet cycle will weaken the waterholding capacity of the soil sample.And soil-water characteristic curve model considering the times of wet and dry cycle is established.According to the saturated permeability coefficient measured by the variable head permeability test,and based on the unsaturated permeability coefficient formula of the VG model,determining the permeability coefficient curve of the soil sample.(3)The SEEP/W module in Geostudio was used to numerically simulate the seepage field of the slope.The results show that the moisture content of the shallow soil layer reaches saturation under the action of rainfall firstly,and the corresponding pore water pressure increases accordingly.After the rainfall ends,the water content and pore water pressure of shallow soils layer decrease,and the decrease of water content and pore water pressure of deep soils layer has hysteresis.The greater the rainfall intensity,the more obvious the hysteresis effect.(4)Through the SLOPE/W module coupled with the results of the seepage field in SEEP/W,analyzing the influence of the dry-wet cycle and rainfall on the slope stability.The results show that the slope safety factor decreases with the increase of the times of dry-wet cycle,and the greater the rainfall intensity,the greater the slope safety factor decreases.Accordingly,a slope safety factor model considering the times of dry-wet cycle is established for different rainfall intensity.When the rainfall intensity is 100 mm/d,the safety factor of the slope is reduce to 1.236 in the 10th drywet cycle,and the slope has the risk of instability.,adopting buttressed retaining wall to reinforce the slope,and the corresponding safety factor of the slope is increase to 1.425 after reinforcement,indicating that the reinforcement measure is effective..In summary,the research in this paper can provide reference for the prevention and control of slope stability of the operating mountainous expressway under the effect of atmospheric dry-wet cycle.