Experimental study on the dynamic modulus of compacted loess under bidirectional dynamic load

The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China,where earthquakes frequently occur.To study the change in the dynamic modulus of the foundation soil under the combined action of vertical and horizontal earthquakes,a hollow cy-lindrical torsion shear instrument capable of vibrating in four directions was used to perform two-way coupling of compression and torsion of Xi'an compacted loess under different dry density and deviator stress ratios.The results show that increasing the dry density can improve the initial dynamic compression modulus and initial dynamic shear modulus of compacted loess.With an increase in the deviator stress ratio,the initial dynamic compression modulus increases,to a certain extent,but the initial dynamic shear modulus decreases slightly.The dynamic modulus gradually decreases with the development of dynamic strain and tends to be stable,and the dynamic modulus that reaches the same strain increases with an increasing dry density.At the initial stage of dynamic loading,the attenuation of the dynamic shear modulus with the strain development is faster than that of the dynamic compression modulus.Compared with previous research results,it is determined that the dynamic modulus of loess under bidirectional dynamic loading is lower and the attenuation rate is faster than that under single-direction dynamic loading.The deviator stress ratio has a more obvious effect on the dynamic compression modulus.The increase in the deviator stress ratio can increase the dynamic compression modulus,to a certain extent.However,the deviator stress ratio has almost no effect on the dynamic shear modulus,and can therefore be ignored.

Large and moderate Ornstein-Uhlenbeck deviations in testing process with linear drift

This paper studies hypothesis testing in the Ornstein-Ulenbeck process with linear drift. With the help of large and moderate deviations for the log-likelihood ratio process, the decision regions and the corresponding decay rates of the error probabilities related to this testing problem are established.

Effects of the mixing degree upstream of the diverging area on the pollutant allocation characteristics of a braided river

The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers,but the effect remains unclear at present.In this paper,physical model tests were designed to study the effect on the pollutant flux ratio with six branching forms and a series of longitudinal discharge distances.The results indicated that the mixing degree upstream of the diverging area,which is closely related to the longitudinal discharge distance,notably affected the pollutant flux ratio.The lower the mixing degree,the larger was the deviation of the pollutant flux ratio from the discharge ratio.Moreover,a linear relationship was attained between the dimensionless mixing degree and the dimensionless deviation of the pollutant flux ratio from the discharge ratio.Consideration of different branching angles or different water layers or different branches did not affect this trend.The experimental results further demonstrated that the intercept and slope of the aforementioned linear relationship depended on the branching angle and exhibited an opposite monotonicity with a symmetric branch angle as the dividing point.These results help towards a better understanding of the mechanism of the factors influencing pollutant transport in complicated braided rivers,and provide a new approach to predicting the pollutant flux ratio of braided rivers.