Mechanical Test Research Of The Granite Residual Soil Considering Small Strain Stiffness And Its Engineering Application

Granite residual soil is widely distributed in our country,especially in the southeast coastal area.Granite residual soil is a kind of special soil,the lack of its physical and mechanical properties research results there are many problems in geotechnical engineering practice in granite residual soil area.The xiamen metro line 2 for five yuan bay south station foundation pit in the quality of the granite residual soil undisturbed and disturbed soil indoor triaxial test and bending test,to study the stress and strain characteristic of the granite residual soil and the influence of structural,and the small strain stage characteristics of granite eluvial soil stiffness.The main contents and results include:1.through indoor soil test basic the basic mechanical properties of soil samples,according to the geotechnical test procedures(SL237-1999)classification of saturated sand powder of low liquid limit soil.2.through to the granite residual soil sample and reshape the conventional triaxial consolidation undrained test samples,studied the granite residual soil stress-strain relationship and its structural.Sample of the triaxial shear test of stress strain curve for strain softening,mostly formation fracture surface destruction;Reshape the kind of stress strain curve for strain hardening model,failure pattern for the drum shape.Soil sample repeated unloading and loading test shows that the stress-strain relationship is a relationship of hardening,including shear stiffness and compression hardening,the unloading modulus of resilience modulus is greater than the main load.3.through the study of the bender elements of granite residual soil sample test test,studied the deformation of rock mass occurs in the early,the soil is in a state of small strain of soil shear modulus characteristics.Its biggest shear modulus than normal strain state shear modulus,and with theincrease of confining pressure,the maximum shear modulus also increases accordingly,and along with the increase of strain decay very quickly.4.xiamen metro line 2,five yuan bay south station foundation pit engineering as an example,discusses the HS-Small model parameters are applied to the applicability of the granite residual soil excavation engineering.Numerical calculation results and the actual monitoring data contrast analysis shows that the HS-Small model can more accurately predict the deflection of the foundation pit excavation,and more consistent with the measured data,can be used as predicting the soil deformation in the calculation of geotechnical engineering.5.excavation unloading of soil as the main characteristics,so the unloading deformation of reload modulus is an important parameter,the HS-Small model parameter scheme through independent uninstall reload modulus,on the basis of considering the characteristics of deformation of soil initial stiffness big,achieve precise analysis of soil deformation.