Study And Engineering Application Of Hss Model Parameters Of Xiamen Granite Residual Soil

Granite residual soil is a kind of special soil with high pore ratio and bearing capacity,but its strength decreases sharply under disturbance or dynamic water pressure.This kind of soil spreads widely in the construction field in Xiamen area.A large number of papers reveal that in most geotechnical engineering,most soil around the structure is in the state of small strain,and in only a few areas it has plastic strain.Compared with large strain,soil mass has higher modulus in small strain range.HSS model can reflect the characteristics of this soil in small strain state.In this paper,a series of laboratory tests were conducted on two different types of granite residual undisturbed soils taken from the second west passage in Xiamen to study the stress-strain characteristics of different granite residual soils.We obtain the whole HSS model parameters,establishing the empirical relationship of main parameters,and analyzing the sensitivity of main parameters to numerical simulation.The main contents and conclusions are as follows:1.The basic mechanical parameters of the soil samples was obtained through basic geotechnical tests in the laboratory.According to the comprehensive classification proposed by Wu nengsen,the granite residual soil taken from the I2 and E foundation pit area is respectively named as sandy clay and silty clay.At the same time,the standard consolidation test shows that the granite residual soil is of medium and low compressibility,while it has a high porosity ratio.2.The stress-strain curves of sandy clay and silty clay show they are in weak and softening state under the tri-axial shear test,and both of them form obvious shear zones.Silty clay and silty sand have higher shear strength than sandy clay.3.The bending element test shows that the shear modulus of the granite residual soil under the condition of small strain is much larger than that of large strain,and its stiffness decreases rapidly with the increase of strain.The parameters of the whole HSS model were obtained,and the proportional relationship between the parameters of the granite residual soil under large strain was not different from that of clay in other areas.For small strain parameters,there is a large difference in the ratio of ₀and,while the value of _0.7is about the same.4.The applicability of HSS model for foundation pit excavation and the reliability of parameters obtained are discussed based on the foundation pit engineering example of area E of the second west passage in Xiamen.The comparison between the numerical calculation results and the measured data shows that the HSS model can predict the excavation deformation more accurately,and the obtained parameters results are more reliable.5.The numerical analysis method is adopted to study the deformation sensitivity of parameters,it shows that small strain parameters have larger impact on deformation,and the parameters under the large strain range has relatively less effects.The proportional relationship of model parameters for two kinds of granite residual soils in large strain range is unified,Finally,the reference table for the value of HSS model parameters applicable to granite residual soil in Xiamen area is obtained.