Design Method And Numerical Analysis Of Geogrid Reinforced Soil Cave

Soil cave is one of the most common geological phenomenons in the karst region,and because its position is so shallow in engineering that the soil lay over the soil cave couldn’t bear large load.It might cause large settlement,that may cause the soil lay suddently collapse even threaten to the huge life and property of the people.Current when geosynthetic is as the reinforced material,it not only could meet the requirements of bearing capacity,strength and durability and bring early warning for engineering disaster because of its flexible.In addition,it can effectively reduce the damage on property,but design method is behind the engineering application for the treatment of soil cave with geosynthetic reinforcemen.Therefor,the study of reinforcement design method has important guiding significance for engineering application.The paper uses the geogrid to treat soil caves and reinforce the soil lay.The characteristics and test methods of the interface between soil and reinforced geogrid are analyzed,and the reinforced mechanism of the level geosynthetic on the soil cave are analyzed.There are mainly the soil arch theory,the membrane influence,soil expansion over the geosynthetic,the friction,the interlocking and the occlusion of the anchoring segment of the overlying soil.When the conditions are different,they play different roles in getting different effectiveness.In addition,the factors of the reinforced soil cave affected the characteristics of the interface are analyzed.According to the mechanical characteristics of geogrid,the horizontal geotextile on the soil cave is divided into dangling segment,transition segment and anchoring segment.Considering the passive resistance of cross rib and the proposed law of friction force of the geotextile,the force and the strain of the segment were derivated and calculated respectively.Geotextile segments stress and deformation equations are obtained,and the anchorage segment are divided into three kinds of conditions according to the activations of the friction force and passive resistance.The derived formula is verified based on in situ test and the results are consistent.And the influence of the soil cave width,geotextile stiffness,the thickness of the overlying soil,soil horizontal rib number to geotextile strain and settlement are analyzed.Finally in-situ test is simulated by the finite element software ABAQUS at the same conditions.The deformation and settlement curve of geotextile were obtained and compared with analytical solution analysis.There is more different in anchoring segment,but others are consistent and the cause is accounted for the difference.Analyzing effect of the soil cave width and thickness of the overlying soil and geotextile stiffness on the soil surface settlement.Further analysis of multi-layer geotextile structure is conducted,and the influence of the settlement and deformation in layer of reinforcement of the number and spacing on the underlying are analyzed.And layers of geotextile strain and the transfer mechanism of the structure are further verified under the same spacing.Three dimension numerical model is conducted on the basis of original two-dimensional model to analyses the reinforced structure.The displacement occurs not only in the direction and also in horizontal direction.And the settlements curve is similar and consistent in both conditions.The influence of transversfe stiff of geotextile on the reinforcement structure was further analyzed.Two-direction with one-direction of stiffness of geotextile on the reinforcement are compared.