Study On Lateral Earth Pressure And Stability Of Retaining Structure With Narrow Width Soil

For the embankment passes through the steep slope,the combined retaining structure(CRS)has the advantages of availability of construction materials,low cost and ease of construction.With the increase of construction of expressways in mountainous areas,the CRS is commonly adopted as an engineering scheme.However,few researches have been conducted by scholars for the performance of the CRS.The width of the embankment behind the CRS is narrow due to the restriction of the steep slope,therefore,the CRS can be considered as the retaining structure with narrow width of the retained soil.For this type of retaining structure,the lateral earth pressure is closely related to the position of the rock face.Because of the complex structure of the CRS,the stability of the CRS and its influencing factors are different from the traditional retaining structure.Based on the characteristics of the CRS constructed on the steep slope,the field test,numerical simulation and theoretical analysis are conducted to systematically study the performance of the CRS with the narrow width soil.Furthemore,the lateral earth pressure on the CRS and the stability of the CRS are further investigated.The main contents are presented as follows.Firstly,the field test was conducted for the CRS that consists of a number of piles,a concrete platform and a gravity retaining wall.The lateral displacement of the CRS,lateral earth pressure on the retaining wall,the vertical earth pressure near the retaining wall and the bending moment of the pile were monitored.The measured results show that the lateral displacement of the CRS is small;the peak bending moment of the pile is less than its yield moment;both the inclination angle of the rock face and horizontal distance between the bottom of the CRS and the rock face slope toe have the influences on the lateral and vertical earth pressures.Coulomb theory is unsuitable to predict lateral earth pressure for the CRS.Secondly,the numerical model was built based on the actual CRS to study the distribution of the lateral earth pressure,the influences of the wall displacement and the filling space behind the CRS on the lateral earth pressure,and the advantages of the CRS.The results show that when the displacement of the retaining wall satisfies the active state,both the lateral earth pressure coefficient and the acting point of the resultant lateral earth pressure are higher than the solutions of Coulomb theory;the presences of the inclined rock formation,the filling space between the platform and the rock face and the retain soil above the elevation of the top of retaining wall are all have influences on the lateral active earth pressure;both the retaining wall and the platform in the CRS play important roles in reducing the bending moment of pile.Thirdly,for the CRS built on steep slope,the width of the retained soil is narrow.Aiming at this characteristic,the numerical models were built to study the embankment retaining wall with narrow width soil,including the development of the inclination angle of the slip surface,the displacement required by the active state,the magnitude and distribution of the active earth pressure,and the slope angle of the embankment.The results show that the critical value of the inclination angle of the rock face is existed.The slip surface develops along the rock face in the cases where the inclination angle of the rock face is more than the critical value.When the slope angle of embankment is more than one specific value and the inclination angle of the rock face is slightly smaller than the critical value,the slip surface develops along the rock face below the elevation of the top of retaining wall,but develops inside the retained soil above the elevation of the top of retaining wall.When the inclination of rock face is more than the critical value,Coulomb theory will overestimate the earth pressure of the embankment retaining wall.Fourthly,the influence of the position of the rock face on the lateral earth pressure was considered,and the calculations of the lateral active earth pressure on the road shoulder retaining wall were devided into several cases based on the different developments of the slip surfaces.The analytical solution for each case was obtained by theoretical analysis,and the critical dimension of the retained soil between Coulomb failure plane and the planar slip surfaces influenced by the rock face was presented.Simultaneously,the numerical models were built,and the proposed solutions were compared with previous experimental results,previous analytical solutions,and numerical results.The results show that the proposed solutions can provide an accurate forecast for the active earth pressure on the road shoulder retaining wall.Finally,the contributions of the component of the CRS to the stability coefficient of the CRS were studied,and the formula for calculating the stability coefficient of the CRS was deduced.The design parameters of piles in the actual CRS were analyzed by the numerical simulation,and the optimal design method of the actual CRS was also discussed.Meanwhile,the stability of the combined retaining structure built on shoulder was also studied.The results show that the size of sectional dimension of the pile has significant impacts on the bending moment and displacement of the pile,as well as the stability in the actual CRS.The friction between platform and rock formation and an appropriate lateral displacement of the retaining wall can effectively reduce the bending moment of the pile.For the combined retaining structure built on shoulder,the influence of rock face on stability of structure is mainly reflected in the anti-overturning coefficient.