| Arsenic sandstone in Ordos area,Inner Mongolia,is a typical unsaturated sand,which is in the dry and semi-arid climate of seasonal frozen area.The physical and mechanical characteristics of Pisha sandstone subgrade soil are significantly affected by dry density,humidity,temperature and load type.In addition,road diseases occur frequently in Ordos area.After freezing and thawing of subgrade soil,the road will appear serious thawing settlement and frost boiling phenomenon,and then form a gully like rut,which seriously affects the normal use of the road,greatly reduces the bearing capacity of the road to the traffic load,thus affecting the effective operation of the traffic[1]and also hinders the economic construction and the development of the transportation industry in this area.Therefore,in order to study the static characteristics of Pisha sandstone subgrade soil under different confining pressure,freeze-thaw times and water content,direct shear test and conventional triaxial test are carried out for the test soil samples,and dynamic triaxial test is used to study the dynamic characteristics of soft rock under different water content and confining pressure.Through the experimental study,the following conclusions are obtained:?1?Routine physical property index testIn this paper,two representative soil samples are taken from the same geographical location in Dongsheng District of Ordos.The particle size characteristics of arsenic sandstone are obtained by particle analysis test,and the optimum moisture content and maximum dry density are obtained by indoor light compaction test,The Yellow Pisha sandstone has a good gradation and a higher dry density than the purple red Pisha sandstone.At the same time,the XRD and XRF diffraction analysis are used to obtain the mineral content and chemical composition of the two kinds of Pisha sandstone.The active component in the Pisha sandstone is the important reason for its strength and stiffness reduction.?2?Direct shear test and static triaxial test of remolded Pisha sandstoneIn order to study the influence of confining pressure,water content and freeze-thaw cycle times on the static mechanical properties of Pisha sandstone,this paper conducts direct shear test and static triaxial compression test on two kinds of test soil samples respectively;simulates the stress-strain relationship,static strength,tangent modulus,internal friction angle and cohesion of Pisha sandstone soil under different freeze-thaw times,confining pressure and water content.The empirical prediction formula of static modulus of resilience under different moisture content,freeze-thaw times and confining pressure is put forward.?3?Triaxial test on remolding Pisha sandstoneThe dynamic triaxial tests were carried out on two kinds of soil samples under different conditions,and the dynamic elastic modulus and damping ratio of Pisha sandstone were studied under different confining pressures and different water content.The dynamic elastic modulus,water content and confining pressure were fitted by software,and the regression formulas of dynamic elastic modulus,confining pressure and water content were obtained.The dynamic elastic modulus,static elastic modulus,water content and confining pressure of soil samples are analyzed by software,the theory of static and dynamic elastic modulus conversion is established.The dynamic elastic modulus can be derived from the simple and easy to measure static elastic modulus.The dynamic modulus can be calculated according to this formula for the soft sandstone subgrade soil without dynamic modulus data. |
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