The Study Of Dynamic Characteristics On Coarse-grained Soils

In the “soil engineering classification standard”,coarse-grained soil is defined as follows: the soil of which coarse grain group,grain size between 0.075 mm and 60 mm,contain more than 50%.Coarse-grained soils have been widely applied in various kinds of engineering construction,such as high rise building foundations,highway or railway subgrade engineering and large earth-rock dam project,because of its good engineering properties such as high shear strength,high load-carrying capacity,greatfillingdensity,excellent permeability,less settlement and deformation.Since its relatively low construction cost and better adaptation to environment,earth and rockfill dam has been commonly used in hydropower construction in our country.Our embankment dams concentrate in the west,which not only have rich water resources,but also high frequency and high intensity number.so,ensure the normal operation and safety of earth-rock dam is particularly important.Because soil mechanical property is very complex,and its dynamic characteristics are affected by many factors,such as drainage condition,load type or size,vibration frequency,vibration frequency and vibrational amplitude.So,dynamic deformation parameters can’t be simply selected from empirical parameters espicially.For some large engineerings,we must use indoor test to simulate the scene of the actual situation of the soil stress to determine these parameters.Therefore,the experimental study on dynamic characteristics of coarse grained soil is necessary for practical engineering.In this paper,the large-scale dynamic single shear apparatus developed by Dalian University of Technology was used to study the characteristics of dynamic shear moduli and damping ratios of dalian limestone to analyze the stress-strain hysteresis curve of coarse grain materials under different confining pressure and dynamic shear strain amplitude.Test results show that the coarse grained soil skeleton curve well conform to the hyperbolic model and the corresponding model parameters were solved.Then,the author analysised the attenuation law of dynamic modulus and damping ratio of coarse grained soil in 10-4 ~ 10-2 strain range.Residual deformation test of Gu Shui limestone rockfill was investigated by means of large dynamic simple shear apparatus to drawn the curves of residual shearing strain of residual volume strain and residual shearing strain and analyse the changing rule of residual shearing strain and residual volume strain under different confining pressure,dynamic stress ratio and vibration times.The residual deformation mode proposed by Zhu-jiang Shen was used to process the test data.Since the residual shear strain calculated by Zhu-jiang Shen modelis larger than the actual value and it always show poor fitness under high confining pressure and dynamic stress circumstance.So I improve residual deformation to deal with this problem.The parameter meaning is clear and the stability is good,the residual deformation under various circumstance can be solved by use only one set of parameters.The research results can provide basis for the seismic design and enrich the study on dynamic parameters of coarse-grained soils.