Seismic Stability of a Tunnel Considering the Dynamic Geologic Parameters of Loess

In this study, Taiyuan loess is used in the analysis of the seismic stability of a loess tunnel. This analysis considers the dynamic parameters of the loess as determined via triaxial compression tests in the literature. In this analysis, the consolidation pressure is converted into the thickness of the overlying loess layer. The spring stiffness and damping coefficients of the viscoelastic boundary are obtained using the maximum dynamic elastic modulus in conjunction with different loess moisture contents and Poisson’s ratios. Additionally, the loess cohesion and internal friction angle are also obtained for different moisture contents. By (1) utilizing the dynamic finite element static shear strength reduction method and the non-convergence rule, (2) taking the safety factor as the assessment standard for loess tunnel stability, and (3) reducing the dynamic parameters of the loess mass until the model calculation is non-convergent, the effects of the moisture content, seismic intensity and loess thickness on the safety factor are obtained. A theoretical basis for the seismic response analysis of this type of loess tunnel is provided by considering the dynamic parameters of loess.     

Performance of High Speed Railway Subgrade Strengthened by Long-Short Piles: Part II—Numerical Modelling

Geotechnical and Geological Engineering - The Yinxi Railway is located in the western region of China. As a high speed railway line connecting Yinchuan-Xi’an, which is of great significance...     

Dynamic Response of Curved Wall LTSLS Under the Interaction of Rainwater Seepage and Earthquake

When water permeates the loess, the strength of the loess will be greatly reduced; thus, it is necessary to study the effect of seepage on the seismic response of a loess tunnel. Fields of structure and fluid are simulated using ADINA, and the calculation model of a curved wall loess tunnel with a super-large section (LTSLS) is established. Rainwater is simulated using an incompressible constant parameter model. Considering the action of near- and far-field earthquake and pulse effects, the Galerkin method is used to solve the interaction of stress and seepage fields. By contrasting and analyzing the maximum principal stress, the minimum principal stress, the maximum displacement of lining and the internal force of the tunnel structure, the influence of rainwater seepage on the mechanical properties of LTSLS is studied, and meanwhile, dynamic responses of LTSLS under the interaction of rainwater seepage and earthquakes are studied. The results show that if rainwater seepage is only considered for shallow buried LTSLS, the pore water pressure of a tunnel is so small that it may be neglected. The damage degree of LTSLS under the interaction of rainwater seepage and earthquakes is more than that under a single field. When considering the interaction effect of rainwater and earthquakes, the pore water pressure, principal stress and displacement under a near-field earthquake with pulse effect are greater than those under a near-field earthquake without pulse effect and a far-field earthquake under the same condition.     

Performance of High Speed Railway Subgrade Strengthened by Long-Short Piles—Part I: Experimental Results

Geotechnical and Geological Engineering - The Yinxi Railway is located in the western region of China. As a high speed railway line connecting Yinchuan-Xi'an, it is of great significance for...     

Seismic stability analysis of subsea tunnels under the effects of seepage and temperature

This study used the strength reduction method to analyze the seismic stability of a subsea tunnel under the effects of seepage and temperature. Excess pore water pressure within the rock mass was first eliminated by calculating the consolidation; then, an earthquake wave was applied to begin the dynamic and time-history analysis and to obtain the maximum horizontal displacement of the model boundary. Finally, a temperature field model was established for the thermal analysis of the structure. The temperature of each node of the structure was regarded as a form of outside load applied to the reduction model; both sides of the vertical horizontal displacement of the boundary nodes and gravity were used as inputs for the static analysis when the vertex horizontal displacement reached its maximum value. By continuously decreasing the shear strength parameters, the safety factor of the tunnel structure was determined. The results show that the plastic zone first appeared in a smaller range on both sides of the tunnel arch feet near the lining and vault of both sides. The safety factor decreased with increasing water depth and overburden layer thickness.     

观音山水库水化学和浮游生物调查及其利用的初步研究

对观音山水库水化学、浮游生物及利用进行了调查研究。（１）库水属Ｓ、中营养型，含盐量很低；营养元素Ｎ／Ｐ平均９５．６，磷是限制性因子。２）浮游生物量平均４．５２４７ｍｇ／Ｌ，其中浮游植物量平均３．０６０６ｍｇ／Ｌ，以硅藻、裸藻和甲藻占优势；浮游动物量平均１．４６４１ｍｇ／Ｌ，以枝角类和桡足类占优势，分别占６９．２％和３０．２％。（３）鱼产力为１１２８ｋｇ／ｈｍ２，鲢、鳙、鲤每公顷放养尾数分别为９２２、６４５和４７０（都在１３．３ｃｍ或１３．３ｃｍ以上）。（４）提出渔业利用意见。