Stability Analysis And Construction Technology Contral Of Subgrade Slope At Fenghuangliang Tunnel Kuimen Side

Stability analysis and treatment measures of high subgrade slopes play a key role in ensuring road traffic safety,and are also the focus of scientific research and engineering technicians.A practical subgrade slope is analysis in this paper,which is around Fenghuangliang tunnel Guimentuan expressway locaded in Chongqing of G42 Hurong expressway.The reasons for instability and landslide of thid subgrade slope are analyzed by field investigation.The safety factor,displacement field,stress field and potential sliding surface of the slope are abtained by using Finite element reduction method,and the treatment scheme is proposed for this subgrade slope,which can provide references for similar projects.The main conclusions of this paper are as follows:(1)The collapse and sliding of ubgrade slopes at Fenghuangliang tunnel Geimen side is mainly due to the damage of drainage ditches at the foot and step of subgrade slope.The rain in ditch would erode the subgrade slope foot during rainstorm.The infiltration of rain into slope not only increases the dead weight of the slope but also reduces the shear strength of the soil.The both factors have caused the collapse of the slope retaining structure and the slide of some slope slopes.(2)Through laboratory tests,it is found that the natural weight of silty clay mixed with debris is 19.34 kN/m3,the saturated weight is 20.75 kN/m3,the natural water content is 23.67%,the cohesion is 28.5 kPa,the internal friction angle is 20.7 degrees,the cohesion is 20.2 kPa and the internal friction angle is 15.4 under saturation.The increase of water contant will significantly reduce the shear strength of subgrade slope soil.(3)The stability of the subgrade slope in natural state is analyzed by using the finite element strength reduction method.The safety factor is 1.263,but the stability of the subgrade slope is obviously reduced by the action of rain,which makes it in an unstable state.The calculation shows that the maximum displacement,stress and shear of the slope are located at the foot of the retaining wall structure,which increases the probability of damage of the retaining wall.(4)Base on the causes of the subgrade slope sliding,the treatment measures of "reinforced concrete anti-slide pile + concrete retaining wall" are proposed.The safety factor is 2.45 by numerical calculation.Compared with the stability before treatment,the stability of the subgrade slope is significantly improved.The anti-slide pile mainly plays the role of resisting the sliding force of the slope body,while the retaining wall at the foot of the slope mainly guarantees the foot of the slope from the erosion of the rain.Finally,the construction technology of the control scheme is expounded in detail,which lays a good foundation for ensuring the quality and construction progress for this project.