Dynamic Triaxial Test and Microscopic Study of Solidified Muddy Soil With Different Mixing Ratios and Curing Ages

Aiming to explore the optimal mixture ratio and curing age of solidified muddy soil under dynamic load, the paper intends to investigate whether the solidified muddy soil can be used as filling of high-speed railway subgrade. Based on the dynamic triaxial test, the investigation measured the dynamic strain and dynamic elastic modulus of solidified muddy soil under different mix ratios and curing ages, and also observed the microscopic morphology of solidified muddy soil samples by using scanning electron microscope. The results show that the addition of cement and curing agent significantly increases the dynamic strength and elastic modulus of muddy soil, which effectively improve the dynamic characteristics of muddy soil. The curing effect of the curing agent is more obvious with the increase of the dosage of cement and curing agent under different mix ratio. The content of curing agent plays a leading role in the hydration reaction between cement, curing agent and soil particles. Additionally, in case of the same test conditions, when the ratio of cement mass to dry silt mass is 1:20, the ratio of diluent volume to dry silt mass is 1:20, with 28 days of curing age, its curing effect will reach the best.

Discriminant Method of Sand Liquefaction

With the proposal of 1.8 billion mus of cultivated land red line and the rise of land reclamation in China, more and more national defense and civil projects are built on poor geological soil, such as reclamation reefs in the South China Sea. The liquefaction damage caused by earthquake, such as water spraying, grouting and surface cracks, has a great impact on such buildings, and poses a threat to people's lives and property. Therefore, it is of great significance to study the liquefaction of sand in foundation soil. Since Academician Huang Wen-xi first proposed to use indoor dynamic triaxial test to study liquefaction, a series of achievements have been made in the liquefaction of foundation soil. The research methods of sand liquefaction have developed from simple single sample of numerical simulation, numerical simulation and test. Referring to the literature at home and abroad, this paper sorted out the discriminant method of sand liquefaction, experimental study of sand liquefaction and post-liquefaction analysis.

Dynamic Characteristics of the Rubber-Tailings Mixture Based on Dynamic Triaxial Test

The liquefaction of tailings is a common failure mode under earthquake actions. The traditional treatment measures of waste rubber have the disadvantages of environmental pollution and occupying soil resources. The combined treatment of waste rubber and tailings is very likely to have important engineering application and theoretical value, and the dynamic characteristics of the rubber-tailings mixture (RTM) are essential and indispensable for handling them together. In this paper, the dynamic triaxial test was used to study the dynamic mechanical characteristics of the RTM. The test was divided into 5 groups with 54 valid samples. The effects of the rubber particle size, rubber content, consolidation pressure, pH value, and soaking time on the dynamic characteristics of the RTM were studied and discussed. The results show that the liquefaction cycle number of the RTM is 50% higher than that of tailings, and the particle cluster effect theory of the RTM is put forward. It will provide a theoretical basis and guidance for the treatment of the waste rubber and tailings.

Test Analysis on the Dynamic Performance of Frozen Silty Clay

Currently, over half of China’s trunk railways are located in permafrost regions. But to tackle the railway subgrade disease has always been the difficulty in the railway construction there. The influence that the dynamics performance of frozen silty clay has on permafrost subgrade is an important component in the researches towards permafrost subgrade. In this paper, the dynamics performance of frozen silty clay in permafrost regions is studied based on the indoor dynamic triaxial test at a low temperature, and at the same time, by studying the influence that several factors like cyclic matrix, confining pressure, temperature and frequency have on relevant dynamics parameters, basis can be provided for the transformation and settlement mechanism of permafrost subgrade as well as for the analysis towards the permafrost’s influence on vibration response under train load, and it offers much reference value to permafrost subgrade’s design.

Dynamic Feature Analysis for Silty Sand

Dynamic shear modulus is proportional to average principal stress.Cyclic varied surrounding pressure isn't proportional to cyclic varied pore water pressure.The dynamic triaxial test with cyclic surrounding pressure can apply cyclic surrounding pressure.The dynamic triaxial test with cyclic surrounding pressure can apply cyclic surrounding pressure in addition to the cyclic deviator stress and it can simulate the coupling of cyclic shear stress and it can simulate the coupling of cyclic shear stress and cyclic normal stress in an earthquakes.