开挖过程的非线性理论分析

本文从岩土介质力学非线性和变形破坏过程自组织非线性的角度对开挖过程岩土体非线性行为进行了探讨。以此为依据,分析了岩土从微观破坏、滑移面形成、直至整体变形破坏全过程的自组织发生机理,在此基础上,建立了伴随开挖过程岩土体变形破坏的非线性动力学描述方程。     

Discrete and continuum modelling of excavator bucket filling

Two-dimensional discrete and continuum modelling of excavator bucket filling is presented. The discrete element method (DEM) is used for the discrete modelling and the material-point method (MPM) for continuum modelling. MPM is a so-called particle method or meshless finite element method. Standard finite element methods have difficulty in modelling the entire bucket filling process due to large displacements and distortions of the mesh. The use of a meshless method overcomes this problem. DEM and MPM simulations (plane strain) of bucket filling are compared to two-dimensional experimental results. Cohesionless corn grains were used as material and the simulated force acting on the bucket and flow patterns were compared with experimental results. The corn macro (continuum) and micro (DEM) properties were obtained from shear and oedometer tests. As part of the MPM simulations, both the classic (nonpolar) and the Cosserat (polar) continuums were used. Results show that the nonpolar continuum is the most accurate in predicting the bucket force while the polar and DEM methods predict lower forces. The DEM model does not accurately predict the material flow during filling, while the polar and nonpolar methods are more accurate. Different flow zones develop during filling and it is shown that DEM, the polar and the nonpolar methods can accurately predict the position and orientation of these different flow zones.     

Laboratory optimization of the soil digging process

A new idea for the optimization of digging using earth-working machinery is presented and experimentally verified. This idea is based on the conclusions derived from previous papers presented by the same authors, that the soil cutting trajectories incorporating the generated shear band as a part of them are the optimal ones. Dividing the whole excavation task into several repeatable cycles for which the soil free boundary before and after the experiment are similar the optimization of a single cycle plays a significant role in the energetic efficiency of the whole task. A single cycle of the working process is defined using several basing parameters. The influence of each parameter on the specific unit energy of the process was experimentally verified. Finally, a set of values for the discussed parameters is recommended for the particular soil and tool shape.     

大跨度深埋黄土隧洞的开挖效应研究

本文研究了大跨度深埋黄土隧洞在其它条件不变的前提下, 全断面开挖时黄土的变形破坏规律和衬砌中内力的分布规律, 指出了它们存在本质区别的原因在于不同的开挖方式, 揭示了开挖的本质, 分析了内力合理分布的条件。     

西南某大型水电站拱肩槽边坡开挖的变形响应研究

对基于结构网格的Euler方程及N-S方程求解器和基于非结构网格的Euler方程求解 器,采用结构模态分析方法和柔度矩阵方法,对无人机大展弦比机翼在Ma=0.6, α=2?, 飞行高度20km的巡航状态下的静气动弹性特性进行了数值模 拟. 验证了两种求解器对静气动弹性模拟的准确性. 同时,对模态分析方法和柔度 矩阵方法进行了对比研究,发现柔度矩阵方法更适用于静气动弹性数值模拟. 另外, 对应用物面法向偏转方法替代网格变形技术模拟静气动弹性进行了研究,计算表明 物面法向偏转方法可以大大提高静气动弹性计算效 率和克服机翼结构变形过大时动网格技术无法处理的不足.     

渗流对岩体高边坡位移的影响

根据渗流场和位移场耦合机理 ,结合某大型船闸工程 ,采用有限元法进行计算分析和对比 ,结果表明船闸在开挖过程中 ,渗流作用力对开挖边坡的稳定性影响很大。并指出对高边坡进行稳定分析时 ,正确考虑渗流作用力的影响十分重要。     

西南某电站河床坝基开挖卸荷条件下变形破坏的数值分析

西南某电站河床坝基开挖过程中,在河床底部出现大量表征岩体卸荷的变形破坏现象。开挖卸荷深度与卸荷强度成为大坝建设及其长期稳定性的关键问题。采用三维有限差分程序FLAC^3D,分析开挖卸荷条件下坝基岩体变形破坏特征。结合现场卸荷裂隙现象调查资料,综合确定出所研究的河床坝基开挖卸荷影响深度及强度。为坝基综合治理提供必要的参考信息,也为今后此类中等地应力边坡开挖卸荷分析储备可以借鉴的资料。     

数值分析模拟开挖卸荷变形的误差分析探讨

岩土体本身的复杂性使岩土开挖变形的数值模拟分析结果与实际有一定的误差。分析产生误差的因素,探讨各误差因素对模拟结果的影响及减小误差的方法,从而可以判断和提高数值模拟结果的准确性。     

龙滩水电站航道座滑边坡平面有限元模拟研究

基于弹塑性有限元（FEM）模型和Mohr-Cou lomb屈服准则,采用平面有限元法对龙滩水电站航道1+016¹+080开挖边坡座滑前的稳定状况进行了数值模拟研究。对座滑前边坡的应力场、位移场及塑性屈服区的模拟结果表明,边坡在座滑前存在明显的塑性区,处于临界稳定状态;开挖过程中边坡存在连续变形,特别是开挖下部时变形会突然增大;座滑前边坡塑性区支护体系已达到承载极限,边坡具备了座滑的条件。     

Study on the efficiency of the digging process using the model of excavator bucket

In the first part of the paper, an experimental program is presented investigating the soil cutting problem, with the application of vertical rigid walls at various widths as the working tools. It was found that when the tool width equalled the width of the soil bin, the soil cutting problems might be treated as plane strain processes. For the tools for which no interaction with the sidewalls of the bin was observed, the zone of the plane strain deformations occurred in the central part of the tools. In the second part of this paper a new experimental program of laboratory tests is presented, for a tool model in the shape of an excavator’s bucket equipped with teeth. The experimental verification of the influence of teeth (number of teeth and the position of teeth on the bucket’s inside lip) on the efficiency of the digging cycle is the aim of this paper. For high values of teeth spacing, the superposition of the plane strain deformation mechanism with three-dimensional failure modes within the soil was observed. For the low values of teeth spacing, the teeth did not act as separate three-dimensional objects but as one wide tool built up from several modules. As a consequence, the deformation pattern in front of such an assembly of teeth was again the plane strain deformation pattern.