Investigation On Characteristics Of Loess Under Seepage Conditions

In loess engineering,soil instability caused by seepage is very common.The soil exhibits different mechanical properties due to different seepage conditions.Most of the previous research results on soil mechanical properties were obtained under the drainage condition or undrained condition.In practical engineering,soil softening instability usually occurs under partial drainage conditions,and the strength parameters of soil under this condition are obviously different from those under free drainage and undrained conditions.Research examples show that different analysis methods(drained or undrained)for soils under the same working condition may result in a difference of more than twice.Therefore,it is necessary to study the triaxial shear characteristics under different drainage conditions in order to obtain more suitable soil parameters in loess area.In this paper,triaxial compression shear and tension shear tests were conducted on undisturbed loess and remolded loess under five drainage conditions by controlling the strain increment ratio.The effects of drainage conditions on the shear properties of saturated loess were analyzed,and the progressive state of saturated loess was studied.The test results showed that drainage conditions controlled the extent to which the shear expansion characteristics of saturated loess were exerted.Under forced water absorption conditions,the shear expansion characteristics of soil were forced to exert,leading to an increase in the asymptotic state stress ratio;Under forced drainage conditions,the shear expansion characteristics of soil are suppressed,resulting in a decrease in the asymptotic state stress ratio.Drainage conditions also affect the accumulation of pore water pressure,thereby changing the stress-strain characteristics of the sample.Under forced water absorption conditions,saturated loess exhibits a trend of shear shrinkage and softening;Under the condition of forced drainage,the specimen exhibits a significant trend of shear expansion hardening.The samples under different strain increment ratios will all reach a progressive state,and the stress ratio in the progressive state has a linear relationship with the strain increment ratio.Finally,the paper uses Geo-studio finite element software to simulate the stability of loess slopes under different seepage conditions,and combines indoor unit tests to modify the strength parameters of loess under different seepage conditions,discussing the impact of seepage conditions on the slope stability coefficient.