Swelling Characteristics Of Experimental Study On The Fully-weathered Expansive Rocks Of Bridge Area Of Jian Shanying Bridge

The JIAN SHAN-YING super large bridge is located in the core of tightly synclinal structure named Chang-ming syncline,which is in the north-south orientation to the Si chuan-Gui zhou meridian tectonic system.This bridge fluctuates abnormally with the local drought and rainy season.In this paper,the background of this study is studied,and the swelling characteristics of exposed fully weathered bare gray shale on the surface of JIAN SHAN-YING region are studied.Here,main factors,such as initial moisture content,dry density and load value,were selected to analyze the change law of rock and soil swelling rate and expansion force under the above three factors.The relationships of expansion force between initial moisture content,dry density,and pressurized loads ware made by experiment.The main research results as follows:Through the microstructure analysis,the whole structure of the expansive rock is mainly flake structure,and the mineral composition is mainly illite,the content is 90.4%,followed by quartz,the content is 9.6%.The experimental results show that the expansion and deformation of the soil can be divided into three stages,concluding:initial slow expansion,accelerated expansion,late stable expansion stage.When the dry density is small,the initial stage with the acceleration phase will be combined.At the same time,the longer the dry density,the longer the sample needs to reach the expansion and stabilization phase.The deformation of the specimen increases significantly with the increase of the dry density in any water content state.The initial moisture content has a greater dry density than the one-dimensional expansion rate of the no-load state.While,the effect of dry density on the size of no-load expansion is greater than that of water.The relationship of equilibrium expansion force of soils and dry density is satisfies the exponential relationship,and the relationship between the expansion strain and the vertical stress is fit for the logistic function of.After seven judging indexes,it is concluded that the expansive rock is a strong expansive rock.At the same time,the free expansion rate is the most accurate and efficient' indicator of the classification and discrimination of expansive rocks.Based on the theoretical results,it is concluded that the expansion and contraction mechanism of the whole weathered expansive rock is dominated by the diffusion theory and the lattice expansion theory.The expansion mechanism of the undisturbed expansive rock is considered mainly to lattice expansion.