The Research On The Layering Standard Of Fujian Granite Weathering Crust Based On The Refined Comprehensive Index

The invasive igneous rocks such as granite,diorite are widely distributed in Fujian province,which is significant to the prevention of landslide,the construction of building foundation and other engineering projects etc.The two test points in Jinzhongshan and Hongping village were chosen in this thesis respectively to study the weathering crust of the two kinds of common invasive igneous rocks in Fujian Province,i.e.,the granite weathering crust and the granite diorite weathering crust.According to the test results,the invasive igneous rock weathering crusts of the test areas were layered.On the basis of the multi-factor orthogonal contrast,the test areas with parent rock were chosen,and a comprehensive comparative study was conducted by means of different tests(such as in-situ standard penetration testing,conventional experimental analysis,cross-hole seismic wave CT,Rayleigh wave test and scanning electron microscopy(sem)test).The different characteristics of weathered layers were studied comprehensively so as to obtain the changing rule(such as quantity,change gradient,trends)of weathered layers.Finally,the weathering crusts was layered accordingly.According to the final test results,the weathering test area can be divided into:shallow residual and diluvial sublayer,deep residual sublayer,completely-weathered layer,granular strong-weathered layer,fragmental strong-weathering layer and medium weathering layer.The final layering result is basically consistent with the those obtained by common method except that the residual and diluvial layer is divided into sublayers,which to some extent validates the scientificity and effectiveness of the layering results in this thesis.Through the comparison of the layering results,the general similarities and differences in the weathering layer structures of the two test areas were further researched.It is indicated that generally the difference in the original rock structures and mineral composition of weathered layers leads to the different physical and mechanics parameters.In addition,the most important layering results were obtained according to the final layering,that is,the residual layers are divided into shallow residual sublayer and deep residual sublayer,respectively.The characteristics of the shallow residual sublayer lie in that the standard penetration number of this layer is less than 10,and the soil is loose and strongly plastic with homogeneous structure,it is mainly composed of fine-grained clay minerals and its condition does not change much in depth.In contrast,the deep residual sublayer is relatively dense to medium dense,it is hard plastic and contains a lot of sand material,it changes a lot in the strength gradient and it is strongly structured.The different weathering agents result in the difference in these two layers.The former is generally influenced by surface weathering agent,whereas the latter is affected mainly by underground water.According to the characteristics of the test results,the test methods of the weathering layers were also compared,and the advantages and disadvantages of different methods in the test of weathering layers are put forward.In addition,with the introduction of the consolidated direct shear test which takes the crustal stress into consideration,it is found that the consolidated direct shear test can reflect the strength characteristics of the weathering layers better than the natural quick shear test.This is because the consolidated shear test based on the original crustal stress can avoid the unloading effect of soil sample and the influence of water content,which makes the test results closer to the strength characteristics of the soil sample itself.