Lu Xiaobing

The evolution of shear bands of saturated soil

Abstract The development of the shear bands of saturated soil in coupling-rate- and pore-pressure-dependent simple shear has been discussed, using a simple model and a matching technique at the moving boundary of a shear band. It is shown that the development of shear bands are dominated by the coupling-rate and pore-pressure effect of the material. The strength of the soil acts as a destabilizer, whilst pore pressure diffusion makes the band expand. The theory is discussed and some computational solutions have been presented.

On the shear instability of saturated soil

Abstract In this paper, the dynamic instability of simple shear of saturated soil is discussed. The governing equations are obtained based on mixture theory in which the inertia effect and the compressibility of grains are considered. Perturbation method is used to analyze and it is shown that two types of instability may exist. One of them is dominated by pore-pressure-softening, while the other by strain-softening.

The instability analysis of saturated soil under shear load

A theoretical description of shear instability is presented in a system of equations. It is shown that two types of instability may exist. One of them is dominated by pore pressure softening while the other by strain softening. A criterion combining pore pressure softening, strain hardening, and volume strain coefficient is obtained and practical implications are discussed.

Instability of saturated soil under axial load

A theoretical description of instability of saturated soil under axial load is presented with a set of equations describing the deformation based on the two-phase continuous media theory. It is shown that all parameters of water and soil influence the instability and two types of instability may exist. One of them is dominated by pore pressure softening, while the other by strain softening. Finally, a practical application is discussed.

一种新的海洋浅层水合物开采法——机械-热联合法

天然气水合物是国家的战略能源之一.天然气水合物分解相变使其开采难度高于常规化石能源.国际天然气水合物试验性开采表明通过降压、注热等方法难以满足商业化开采的需求,尤其在水合物位于浅层、软土情况下,持续稳定且高效率的热量供给是其瓶颈.天然气水合物机械-热联合开采是一种新概念模式,即通过粉碎水合物沉积物通过管道输运并在内部分解,这样既增加了传热的表面积,又利用海水热量和对流传热提高了能量供给效率.分析表明：利用该方法开采时水温过高会导致水合物分解过快而产生不稳定流,温度过低又导致水合物二次生成或结冰;水流流速既要能使被粉碎的水合物沉积物颗粒悬浮和流动,又不能导致流动失稳.为了实现高效安全的机械-热水合物开采,经过初步分析提出原位水合物地层粉碎的颗粒直径设定在0.1～1.0 cm之间,控制水流速度为0.22～0.67 m/s,温差保证在5 K以上,混合物中水的体积分数大于0.85.

The responses of casing pipe of oil-well induced by the swelling of rocks

The responses of casing pipe of oil-well induced by the swelling of rocks are investigated by numerical simulation. It is shown that the swelling of rock may cause severe permanent plastic strain of the steel casing pipe. The displacement of the pipe without a lining is 58% larger than that with a lining under the same volume swelling condition. A lining may decrease the pressure of the casing pipe caused by the dilation rock. There exists necking phenomenon. The necking of the pipe with a cement lining is larger than that without the cement lining.

Shear instability of saturated soil considering the gradients of strain and pore pressure

The dynamic instability of saturated soil considering the gradients of strain and pore pressure was discussed in this paper. The inertia and the drainage effects were considered and the Perturbation method was used. It is shown that the strain gradient and pore pressure gradient are positive factors for the instability of saturated soil.

Application of Artificial Network in Forecasting Liquefaction of Saturated Sandy Soil

The forecasting of liquefaction of saturated sand is difficult because of its complexity, but it is of importance in practice. The technique of artificial neural network is used to model the forecasting of liquefaction phenonmenan. The dimension analysis is processed, based on which a concise architecture of BP network is built then. It is shown that artificial neural network is an effective tool in forecasting of liquefaction.

Development of the Shear Bands in Saturated Soil

This paper describes the development of shear bands in saturated soil under simple shear using a matching technique at the moving boundary of a shear band, and it is shown that the development of shear bands is affected by the coupling strain rate and pore pressure of material. Some numerical solutions have been presented.