Study On Structural Origin And Seepage Failure Mechanism Of Granite Residual Soil

Granite residual soil is widely distributed in South China and southeast of China.Due to its characteristics of water disintegration and rapid attenuation of strength after disturbance,it has caused many engineering accidents.It is a typical regional soil.The root of the particularity of all soils ultimately comes down to their mineral chemistry.The particularity of granite residual soil in South China and Southeast China lies in the mineral chemical composition of granite parent rock and its natural multi-fissures,which makes it form a special "structure" after weathering under humid,hot and rainy climate environment.Although we have already had a lot of literature to explore the particularity of the granite residual soil and the engineering characteristics of granite residual soil and its structural already had certain understanding,but,at present also lacks the mineral chemical composition in the evolution of south China,southeast and the formation of the special "structural" in-depth analysis,therefore,understanding of the specificity of the granite residual soil also is not very clear.There is no recognized constitutive model for granite residual soil under the disturbance of water,stress unloading(excavation)and pile driving vibration in our country.Based on the above considerations,this paper mainly carries out the following research work: analyze the weathering characteristics of granite from north to south in China,and highlight the influence of climate conditions on the weathering process of granite in South China;Taking the grain gradation curves of several soil samples as an example,the lack of intermediate grain size(poor gradation)phenomenon widely existed in granite residual soils in South China was investigated,and its relationship with structure was analyzed.By comparing the seepage failure tests of undisturbed soil and remolded soil,the view of structural vulnerability caused by poor gradation of granite residual soil is indirectly demonstrated from the point of view of critical seepage slope.The results of this study show that the special humid,hot and rainy climate,rich groundwater flow and acidic water environment in South China and Southeast China formed the deep granite residual soil layer and its special structure in this region.The structure of granite residual soil in South China and southeast China is due to the poor grain gradation characteristics and the corresponding fabric characteristics.Under the action of seepage,the intact granite residual soil in South China and southeast China is easier to be destroyed than the remolded soil,and the intact soil will be damaged by piped-type,which can better explain the structural mechanism of the granite residual soil in this area.