Study On Pore Pressure And Deformation Of Saturated Frozen Quartz Powder Under Variable Load And Temperature Conditions

The foundation in permafrost areas is prone to uneven settlement and cracks when the external temperature and load change,which not only poses a huge threat to the safety of buildings built on it,but also increases the cost of late r maintenance.The deformation of frozen soil is closely related to pore water pressure.Currently,there have been many achievements in the study of pore water pressure,but there is less research on pore water pressure under negative temperature conditio ns.This article uses a self-made device to carry out physical properties tests of saturated quartz powder,stepwise loading tests under different temperature gradients,and stepwise heating tests under constant load.The variation law and influencing fact ors of pore water pressure and deformation of saturated frozen quartz powder were analyzed from the perspectives of variable load and temperature.The following main conclusions were obtained through indoor experiments:(1)The higher the initial dry densi ty of the quartz powder sample,the smaller the saturated moisture content,and the lower the freezing temperature.After the sample freezes,the higher the initial dry density,the lower t he unfrozen moisture content under the same temperature conditions.(2)The particle size of quartz powder is consistent,with a single composition and morphology.At lower temperatures,the pores of frozen quartz powder are interconnected and have strong permeability.When the load and temperature are increased,the pore water seepage rate accelerates.(3)During the progressive loading process of saturated frozen specimens under different temperature gradients,the pore water pressure and deformation ampl itude are closely related to temperature,initial dry density,and load.When the temperature is low,the unfrozen water content is small.As the overlying load gradually increases,the amplitude of pore water pressure changes gradually decreases,and the amplitude of sample deformation changes also gradually decreases;W hen the temperature is high,the unfrozen water content is high,and the soil skeleton stiffness is small.As the overlying load gradually increases,the amplitude of pore water pressure an d deformation changes gradually increases.Under the same temperatu re and load conditions,the higher the initial dry density,the smaller the saturated water content,the smaller the pore ratio,and the smaller the amplitude of changes in pore water pressure and deformation.(4)During the gradual temperature rise test o f saturated frozen quartz powder under constant load,the temperature gradually increases,the ice cement gradually melts,the unfrozen water content increases,and the ability to resist co mpression deformation weakens.Under the action of load,the pore w ater pressure and deformation changes gradually increase.Under the same initial dry density conditions,the larger the overlying load,the greater the amplitude of pore water pressure and deformation changes,and the pore water pressure and deformation ch anges of melted quartz powder are much greater than those of frozen quartz powder.