Papers by Keyword: Stress and Deformation

Abstract: Abstract: The stress and deformation of rock-fill dam with asphalt concrete core wall founded on deep overburden is calculated and analyzed by Duncan E-ν model and double-yield-surface model through three-dimensional finite element method. The stress and deformation of dams in water storage period is compared by the two models, the results show that the deformation distribution of dam core via two different models are coincide one another. The horizontal displacement and vertical displacement of rock-fill dam with asphalt concrete core wall by double-yield-surface model is smaller than which by Duncan E-ν model in the period of water storage. Furthermore, the horizontal displacement and vertical displacement by double-yield-surface model, which are close to the practical test data through the deformation via two models are in good agreement. The analysis of core-wall stress via double-yield-surface model is more reasonable than the Duncan E-ν model. The analysis result of resisting hydraulic fracturing of core dams by DuncanE-ν model is coincide which of core dams by double-yield-surface model.

Abstract: The earth-rock cofferdam on deep overburden is the main study object. The cofferdam filling and dam excavation process were numerical simulated using FEM code ANSYS .Main research focused on stress and deformation characteristic of cofferdam and concrete cutoff wall during completion and excavation process.Analysis showed that displacements of cofferdam and cutoff wall distribute well in x, y, z directions with acceptable magnitude, stress characteristic values are less than design standard. The results indicate that cofferdam and cutoff wall are safe and stable both in construction and operation.

Abstract: This paper takes the Section 201 of shield construction engineering in Dalian Metro Line 2 as an example to analyze the deformation law of surrounding soil and the tunnel lining structure stress during shield tunnel construction. The shield tunnel construction is simulated dynamically by ADINA and the shield tunnel structure model of the concrete lining is established. This model is a three-dimension nonlinear finite element calculation model concerned with the grouting soil and original state soil. Taking the soil lithology in the upper layer and interact influences, we analyzed the dynamic process of shield construction, soil grouting and lining supporting and the stress distribution in difference reinforced concrete supporting segments and the ground settlement characteristics. Through numerical analysis method to study the deformation law of soil surrounding tunnel and the stress in tunnel lining, we get the results to compare with the results of Peck formula under the same condition. After generating the conclusions, we can provide several suggestions for shield tunneling construction, lining segment design and control of the ground surface settlement during the construction.

Abstract: Existing research results have indicated that dam material’s rheology under a high stress state is quite evident. In order to study the influence of dam material’s rheology on the stress and deformation of a CFRD, a nine parameter power series rheology model is adopted to analyze the stress and deformation of a high CFRD considering the dam material’s rheology. Calculation results show that since an obvious increase in dam body’s deformation occurs after considering the rheology characteristics of rock-fills, dam body’s stress tends to relax. Rockfill’s rheology characteristics increases the deflection of a face slab to a certain degree, face slab’s slope and dam’s axial maximum tensile stresses rise somewhat as well. As for a high CFRD that face slabs are placed in stages and water impounds in stages, a proper rheology constitutive model is adopted to correctly simulate rock-fill’s rheology characteristics, and results from this modeling can be used for reference for the determination of dam’s filling schedule and face slab’s staged placing and have important meaning for correctly predicting dam’s stress and deformation.

Abstract: The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

Abstract: Pit excavation influences the stress and deformation of adjacent underground pipelines seriously. On the base of former study, the project was analyzed with the aid of general finite element soft ABAQUS, in which the interactive action of soil with pipeline and pit protection structure were taken into account. Wall-soil friction and pipeline-soil friction contact were used. The influence on adjacent pipelines of pit excavation was analyzed. The laws of deformation and the stress were gained. The results showed that the horizontal displacement was much bigger than the vertical displacement, and the pipeline would lift at the end close to the symmetric plane and fall at the other end. The displacement would decrease with the increment of the distance between pit and pipelines. The laws of influence of the pipeline’s embedment and wall-soil friction were similar, while the latter’s influence was greater than the former’s. The influence on horizontal displacement aroused by wall-soil friction was greater. The principle tensile stress mainly aroused by the pipeline’s horizontal displacement would cause tension fracture. The sections of the pipeline around the area of the end and the middle of the pit were dangerous, which should be particularly protected.

Abstract: Three-dimensional digital oral treatment technology based on anatomical features of jaw bone and teeth was applied for modeling. Three dimensional finite element models for the restorative systems with straight glass fiber post, screw glass fiber post and one-piece glass fiber post-and-core were established. Stress and deformation under external bite force were calculated and compared among different post types. Comparing the maximum von Mises equivalent stress in the whole restorative system for the straight post, the screw post and the one-piece glass fiber post-and-core finds that the one-piece glass fiber post-and-core is effective to lower the maximum stress and obtain uniform stress distribution of the teeth. Even in each part of the restorative system like post, crown and root, the maximum stress in the case of one-piece glass fiber post-and-core is still lowest. Using one-piece glass fiber post-and-core, the overall deformation of the restorative system is decreased greatly.

Abstract: The C-type expansion bolt is a new kind and new structural bolt. It has superior compatibility to the soft rock and the big distorted tunnel. In order to study its stress, deformation and interaction mechanism, large distortion calculations and analyses have been carried out on the bolt by FEM (finite element method), especially with the ANSYS software, based on the updated Lagrangian law. The results show that the maximum stress and deformation of the section and body of the bolt meets the anchoring requirements. The bolt meets the required anchoring performance and anti-drawing performance. The paper provides some basis for its design, application and anchoring stress analysis.

Abstract: As a competitive dam style and full of life-force, the concrete- faced rockfill dam (CFRD) is widely used in China in recent years. Experts in China pointed out that “Extra high CFRD generally means those CFRDs with their heights higher than 150 m ” However, the history of construction and design of extra high CFRD is short and some problems during the construction of Extra high CFRD is still need to be explored. Therefore, stress and deformation characteristic of DongQing extra high CFRD was analyzed by 3D finite element method and some beneficial reference was obtained. Firstly, the advanced 3D mesh generation procedure written by Fortran language was used to form the finite element mesh which contained not only the dam with large amount of vertical joins and perimeric joints, but also the rock foundation and surrounding mountains. Moreover, the layer by layer construction procedure of dam was detail considered during 3D mesh generation. Since the node number of 3D mesh is still larger, large scales equations solving method-element by element method and others efficient measures were adopted. As the results, the computer calculation time decreased from former 48 hours to 20 minutes. According to the calculation results, the design scheme of DongQing CFRD was finally optimized.