Tongchun Li

Failure problems in soils. An enhanced strain coupled formulation with application to localization problems

ABSTRACT In order to accurately model the behaviour of geostructures it is usually not possible to neglect the effect of pore pressure. The resulting displacement-pore pressure formulations give rise to numerical instabilities unless a certain mathematical requirement known as the Babuska-Brezzi inf-sup condition is met. Classically this was done by increasing the interpolation degree of displacement with respect to pressures. However it is possible to obtain stable formulations circumventing the interpolation degree requirement. This article presents a new formulation in which stabilisation is achieved through an approach based on the Simo-Rifai enhanced strain element.

Influence of Construction Method of Arch Dam Foundation Replacement Block on Dam Safety

In order to guarantee the strength and stability safety of dam, it is need frequently to replace weak rock structure with concrete in the process of excavation of arch dam foundation plane. Usually there are two kinds of replacement way, one kind is taking this part of replacement block as the part of dam, which has the advantages of convenient construction and the disadvantages of irregular form of the dam; The other kind way is taking the replacement block as the part of foundation, it means pouring the replacement block in advance, and then pouring dam body when its internal temperature fall at the same as the bedrock, which has the advantages of regular form of the dam and the disadvantages of complex construction lead to influence construction progress. Therefore, the engineering designers pay more attention to the issue that rational evaluation on the influence on the strength and deformation of dam by these two different construction ways. In this paper, as an example of xiluodu, the full-process emulation calculation and study is conducted for the temperature and stress of the high arch dam during construction period period, so as to figure out the distribution and variation rule of temperature and stress and make a rational evaluation on the influence of two kinds of construction scheme on the strength and deformation of the dam. The study provides the helpful evidence for the choice of the concrete pouring ways of the foundation replacement of xiluodu dam.

A generalized plasticity model for sands and its experimental verification

The fundamental theory of generalized plasticity is proposed in detail. With the framework of the theory, irreversible plastic deformations during loading and unloading are introduced without specifying any yield or plastic potential surfaces explicitly and the soil behavior under complicated stress path can be simulated. A generalized plasticity constitutive model for sands, Pastor-Zienkiewicz model, is illuminated. All the parameters with definite physical significance in the model can be determined by indoor experiments. Amount of experimental data are utilized to verify the predict capability of the proposed model. The results indicate that the sand behaviors with the conditions of undrained, drained and cyclic shearing can be reproduced properly by the model.

Hydraulic Vibration Analysis of Bulb Tubular Pump-House Considering Foundation Radiation Damping

On the basis of pressure pulsations recorded at some locations, the pressure pulsation field of the whole flow passage is structured. Dynamic time-history analysis of pump-house of Huaiyin third pumping station caused by pressure pulsations are carried out to calculate dynamic responses of large-scale bulb tubular pump-house. Compared with the conventional method of fixed boundary with no weight foundation, numerical values of dynamic responses reduce by about 50% at the most considering foundation radiation damping, and the influence of the factor is very prominent to dynamic responses of Huaiyin third pumping station. At the same time, control standards of anti-vibration safety are proposed to evaluate vibration of pump-house. The results indicate that Huaiyin third pump-house meets the requirements of the suggested standards.

Study on the Effect of Fluid-Solid Coupling and Foundation Radiation Damping on Seismic Response of Arch Dam

Effect of dam-water-foundation dynamic interaction and foundation radiation damping were considered in the course of the seismic response time-history analysis on WuDongde arch dam, with generalized Newmark algorithm method and transmitting artificial boundary condition. By comparing the numerical results with the conventional method of the massless foundation with fixed boundary and without considering fluid-solid coupling effect, the influence of fluid-solid coupling and foundation radiation damping for seismic response of arch dam were obtained. The results show that the seismic response of arch dam increase almost 25% with considering the effect of fluid-solid coupling of water-dam and the seismic response decrease about 20%∼40% with considering the effect of foundation radiation damping.

Numerical Modeling of Initiation and Propagation Phases of Landslides

This paper deals with initiation and propagation of landslides, for which suitable numerical models are presented. Concerning the initiation phase, we present a coupled displacement-pore pressure formulation (u-pw) proposed by Zienkiewicz and co-workers. Particular attention is paid to capture of the failure surface where strain localizes. An example is presented where the triggering mechanism is the pore pressure changes induced by rainfall. Once failure has been triggered, propagation is analyzed using an Eulerian formulation of the balance of mass and momentum equations. Two simplified, one-phase models are presented for the two extreme cases of dry granular flows and mudflows. The first model uses a level set algorithm to track the free surface, and is suitable for length scales of 100 m. For longer distances of propagation, we propose a depth integrated model which is discretized using a Taylor-Galerkin technique.