A 3D distinct lattice spring model for elasticity and dynamic failure

A 3D distinct lattice spring model (DLSM) is proposed where matter is discretized into individual particles linked by springs. The presented model is different from the conventional lattice spring models where a shear spring is introduced to model the multibody force by evaluating the spring deformation from the local strain rather than the particle displacement. By doing this, the proposed model can represent the diversity of Poisson's ratio without violating the rotational invariance. The local strain of the spring is calculated through a least square method which makes the model possessing meshless properties. Because of this and explicitly representing the microstructure, DLSM is able to model dynamic fracturing problems and can be used to study the microstructure influences. The material parameters inputted in the model is the conventional material parameters, e.g. the elastic modules and the Poisson's ratio. Relationships between microscopic spring parameters and macroscopic material constants are derived based on the Cauchy–Born rules and the hyperelastic theory. Numerical examples are presented to show the abilities and properties of DLSM in modeling elastic and dynamic failure problems. Copyright © 2010 John Wiley & Sons, Ltd.     

Implementation of a coupled plastic damage distinct lattice spring model for dynamic crack propagation in geomaterials

This paper studies dynamic crack propagation by employing the distinct lattice spring model (DLSM) and 3‐dimensional (3D) printing technique. A damage‐plasticity model was developed and implemented in a 2D DLSM. Applicability of the damage‐plasticity DLSM was verified against analytical elastic solutions and experimental results for crack propagation. As a physical analogy, dynamic fracturing tests were conducted on 3D printed specimens using the split Hopkinson pressure bar. The dynamic stress intensity factors were recorded, and crack paths were captured by a high‐speed camera. A parametric study was conducted to find the influences of the parameters on cracking behaviors, including initial and peak fracture toughness, crack speed, and crack patterns. Finally, selection of parameters for the damage‐plasticity model was determined through the comparison of numerical predictions and the experimentally observed cracking features.     

Development of the distinct lattice spring model for large deformation analyses

This study develops the distinct lattice spring model (DLSM) for geometrically nonlinear large deformation problems. The formulation of a spring bond deformation under a large deformation is derived under the Lagrange framework using polar decomposition. The results reveal that the DLSM's stiffness matrix under small deformations is the tangent stiffness matrix of the DLSM under large deformations. The formulation of the spring bond internal force under a given configuration is also presented and can be used to calculate the unbalanced force. Using these formulations, three nonlinear solving methods (the Euler method, modified Euler method, and Newton method) are developed for the DLSM with which to tackle large deformation problems. To investigate the performance of the developed model, three numerical examples involving large deformations are presented, the results of which are also in good agreement with the analytical and finite element method solutions. Copyright © 2013 John Wiley & Sons, Ltd.     

Validation study of the distinct lattice spring model (DLSM) on P-wave propagation across multiple parallel joints

A validation study of the distinct lattice spring model (DLSM) for wave propagation problems is performed. DLSM is a microstructure-based numerical model, which is meshless and has advantages in modelling dynamic problems where stress wave propagation is important. To verify the applicability of DLSM to modelling wave propagation through a discontinuous medium, the virtual wave source (VWS) method is used to obtain analytical solutions for wave propagation across a jointed rock mass. Numerical modelling results of the commercial code UDEC are selected as the reference. The effects of particle size and lattice rotation angle on wave propagation are first studied. Then, the results of wave transmission across a single joint with a different joint stiffness and across multiple parallel joints with different joint spacings are derived with DLSM, UDEC and VWS. These results are in good agreement with each other. Therefore, the capability of DLSM to model P-wave propagation across jointed rock mass is verified, which provides confidence for the further application of DLSM to modelling more complex problems.     

Graphics processing unit based parallelization of the distinct lattice spring model

This study reports a Graphics Processing Unit (GPU)-based parallelization of the Distinct Lattice Spring Model (DLSM) for geomechanics simulation. The DLSM is a newly developed numerical model for rock dynamics problems, i.e., dynamic failure and wave propagation. Despite its applicability, one of the drawbacks of this model is the high computational load for practical simulations. To tackle this problem, a GPU with a Compute Unified Device Architecture (CUDA) is adopted to parallelize the DLSM code. The performance of the GPU DLSM code is tested on two computers equipped with modern GPU cards. The results show that significant performance improvements are gained from GPU parallelization of the DLSM code (the maximum speed up achieved was 23×).     

Elastically-homogeneous lattice models of damage in geomaterials

This study involves the development of the auxiliary stress approach for producing elastically-homogeneous lattice models of damage in geomaterials. The lattice models are based on random, three-dimensional assemblages of rigid-body-spring elements. Unlike conventional lattice or particle models, the elastic constants of a material (e.g., Young’s modulus and Poisson’s ratio) are represented properly in both global and local senses, without any need for calibration. The proposed approach is demonstrated and validated through analyses of homogeneous and heterogeneous systems under uni- and tri-axial loading conditions. Comparisons are made with analytical solutions and finite element results. Thereafter, the model is used to simulate a series of standard laboratory tests: (a) split-cylinder tests, and (b) uniaxial compressive tests of sedimentary rocks at the Horonobe Underground Research Laboratory in Hokkaido, Japan. Model inputs are based on physical quantities measured in the experiments. The simulation results agree well with the experimental results in terms of pre-peak stress-strain/displacement responses, strength measurements, and failure patterns.     

浙江泰顺承天氡泉热储概念模型探讨

泰顺承天氡泉地处断陷盆地边缘,元古界基底隆起区。在资料搜集整理和实地调查的基础上,分析了其控矿因素,研究了地热地质条件,提出了泰顺承天氡泉热储概念模型。     

基于迟滞排泄水箱模型模拟岩溶断流泉水文过程

传统的连续排泄水箱难以模拟岩溶泉断流现象,通过将表层岩溶带调蓄水箱对管道水箱的补给设置为迟滞排泄模式,模拟岩溶断流泉水文过程,并应用于丽江市黑龙潭岩溶泉域。研究结果表明,该模型较好地模拟了泉群流量动态及断流现象;当降雨量明显增大时,通过表层岩溶带调蓄水箱进入裂隙水箱的水量变幅不明显,而管道水箱的分配水量迅速增加,反映了集中补给的大气降水在岩溶系统中形成快速流的过程;黑龙潭泉群水量的绝大部分（82%~95%）来自于管道水箱,岩溶水流在时间和空间上分配的不均匀性易导致泉群断流。该研究提供了将水箱模型应用于岩溶断流泉模拟的参考,有助于理解该类型岩溶水系统的水文过程。     

基于泉流量过程线的管道流与裂隙流识别

??根据岩溶含水系统的双重特性,岩溶含水系统出口处泉流量可分为三个组成部分—前期蓄水量,快速径流和慢速径流,将快速径流和慢速径流视为两线性并联水库,经过系统的调蓄作用,得到一个单位降雨脉冲下快速流和慢速流的响应函数,建立了前期降雨和瞬时单位线之间的识别函数,识别降雨在岩溶不同空隙类型中的水量分配系数。将该函数模型应用到后寨河岩溶小流域,通过参数识别,结果表明从上游到下游前期蓄水量呈现增加的趋势,而水量进入到管道中的分配系数呈现递减的趋势,说明岩溶裂隙结构越往下游越发育,这一研究结果和实际情况相符,说明该模型有一定的适应性,但由于模型假设岩溶系统是线性变化的,所以该模型不适用于大流域以及长期的泉流量预测。      

预应力锚索格构梁作用下边坡土中应力分布的室内模型试验研究

预应力锚索格构梁由于其多方面的优点而在工程中得到了广泛的应用。但到目前为止，对预应力锚索格构梁的设计计算还没有提出一个合理的计算模型。本文针对现有计算模型对格梁底部地基反力的分布假设的不足，进行了预应力锚索格构梁的室内模型试验，并对格梁底部土体应力的实际分布情况进行了分析。分析结果显示，土中应力随锚索预应力的增大而增大，且格梁底部的基底反力并非成直线或线性变化，而是与所加锚索的位置有关，因此不能简单地将格构梁看成刚性梁。最后，就本模型试验所存在的不足对今后的研究方向提出了几点建议。     

山西娘子关泉水及污染成因再分析

山西娘子关泉水是我国北方最大的岩溶泉水之一,也是世界著名大泉,上世纪80年代前多年平均天然流量12.6 m3/s。文章利用1∶5万娘子关泉域岩溶水文地质环境地质调查项目勘探调查成果,对以下2个问题开展再分析:（1）娘子关泉水的成因,勘探等资料表明绵河南岸五龙泉、苇泽关等泉组主要接收下部中、上寒武统含水岩组岩溶水的补给,而非前人研究来源于上部中奥陶至下奥陶含水岩组补给;（2）结合水文地质条件,采用同位素等方法分析,认为部分地区煤矿老窑水的出流是导致娘子关泉水近年来加速污染的主要原因。      

济南泉域岩溶地区多源多尺度数据三维耦合模型及应用

为解决济南城市轨道交通建设与地质环境、保泉供水及建构筑物之间的矛盾,实现泉水保护与轨道交通建设双赢,研发了三维城市地质信息管理与应用系统。根据济南泉域富水岩溶的特点,采用现场工作、室内实验、理论研究、数值分析、成果集成应用等综合研究方法,设计了基于MapGIS 10的三维地质环境信息系统,建立了济南城区标高-350 m的三维可视化地质模型、岩溶模型和水位动态模型,形成了岩溶区三维地质建模的系统方法。为济南轨道交通建设及保泉供水提供了重要管理和应用平台,为济南城市轨道交通的规划、建设、管理提供决策依据,作出更科学的分析和预测。     

地震工况下兰州南绕城高速公路路堑高边坡格构支护效果评价

以兰州南绕城高速公路已加固典型路堑高边坡为研究对象,利用AutoCAD及ANSYS软件建立所选典型边坡的三维数值模型,在此基础上运用有限差分软件FLAC3D对其在地震工况下的稳定性进行科学评价,目的是为黄土类高边坡工程防护及安全设计提供参考。得出的结论为：当水平向地震加速度为0.1g和0.2g时边坡处于稳定状态,水平向地震加速度为0.3g时边坡处于基本稳定状态,水平向地震加速度为0.4g时边坡处于不稳定状态。研究表明,格构锚杆支护承受了大量拉张应力及剪应变增量等,效果显著,对边坡稳定性发挥了重要作用。因该公路建设区抗震设防烈度为8度,地震加速度设计为0.2g,所以地震工况下的所选格构支护边坡处于稳定（稳定系数为1.15）状态,能够满足规范要求。     

A lattice type model for particulate media

In this paper, a lattice-type model to simulate the micro-mechanical behaviour of particulate/granular media is presented. In this numerical model, a particulate assembly is simulated as a lattice/truss. Nodes located at contacts between a particle and its neighbours are linked by bars to each other. Each particle is represented by a lattice within its microstructure and particle interact through load transfer at the nodes. Constraints are prescribed at the nodes to describe active, deactivated and reactivated contacts. When a particulate assembly develops into a mechanism (deformation with zero incremental load), further deformation is simulated through a framework that describes the kinematics of the particles (sliding, rolling and rotation of particles). This framework is formed by introducing nodes at the particle centroids and linking them with bars. Bars-linking particles with a non-sliding contact are assigned large stiffnesses relative to bars linking particles with a sliding contact. Numerical tests are conducted on two-dimensional assemblies of disks, arranged as very loose and very dense packing under simple shear loading conditions. The results concord with the results of numerical tests conducted using the discrete element method and with photoelastic experiments. Additionally, the model is applied to study the effects of initial imperfections caused by particles with low elastic modulus. Copyright © 1999 John Wiley & Sons, Ltd.     

三维地质模型构建方法的研究及应用

地质体三维建模是地学信息系统的核心问题之一.对三维GIS及地学领域的空间构模方法的现状进行分析,结合地质体工程特点,提出一种三维地学空间构模方法--似三棱柱(STP)法.该方法以似三棱柱体作为三维地质体建模的基本体元,并采用5类基本元素和6组拓扑关系对似三棱柱体的数据结构进行描述.它能有效地表达各种三维地质现象,也可以更好地与传统的多层TIN模型结合,维护好空间实体的拓扑关系.基于本文的建模方法开发了一个适合地质领域的三维GIS初步原型,并用实际钻孔数据进行了验证.     

水电三维地质模型中各地质要素的建模方法

决定水电工程地质分析成败的主要环节是地质实体的模拟。用三维数值地质实体模型来模拟实际工程施工过程,可以协助解决各种工程地质问题。介绍了水电工程中地质模型的各个要素（地形面、基岩面、岩层界面、构造界面、透镜体、地层单元、勘探工程以及地质实体）的创建方法、实现思路以及可视化显示,基本包含了水电工程地质分析所涉及到的所有方面。     

黑龙江虎林四平山热泉型金矿床地质特征及成矿模式

四平山热泉型金矿床产于环太平洋成矿带的完达山脉东麓。金矿体赋存于白垩系上统大塔山林场组和四平山组地层的硅化带中。岩石化学,氢、氧、硫同位素地球化学及围岩蚀变特征等研究表明: 该矿床的成矿流体成分中既有大气降水,也有岩浆水的加入,以大气水为主,具有岩浆水与大气降水的双重性质; 成矿物质主要来源于地下岩浆热液的分异,少量来源于高背景的围岩; 成矿热源来自于岩浆的余热。结合该矿床产出的构造环境建立了该矿床的成矿模型。     

济南十大泉群特征、形成模式及水循环差异性浅析

为了全面系统地认识济南十大泉群,文章采用对比分析法揭示十大泉群分布、流量、景观及水质特征,通过水文地质结构精细刻画与泉水排泄条件分析,进一步明确十大泉群成因差异性,归纳泉水形成模式,揭示十大泉群水循环的差异性。结果表明：十大泉群基本特征可大致分为两类,即排泄区6个泉群均为上升泉、南部补给区4个泉群均为下降泉;十大泉群形成模式可划分为五类,即构造凸起—灰岩“天窗”成泉、构造凸起—裂隙连通成泉、浅埋多层砂层与高渗透黏土导通成泉、断裂切割成泉和侵蚀溢流成泉模式;宏观上济南十大泉群水循环受北倾单斜构造控制,其输入条件、输导系统和输出方式差异较小;微观上6个承压型泉群泉水输出方式差异性明显,其灰岩覆盖层类型、厚度、渗透性及灰岩顶板埋深差别较大,导致泉水出流形态、流量及水质不同,形成各自独特的景观。岩溶泉水微观成因的详细研究可为济南十大泉群分类保护提供重要地质依据。     

二维明渠非恒定流的格子Boltzmann模拟

根据二维浅水波方程的特点,应用由格子Boltzmann方程展开的多尺度方程,建立了一个能模拟二维明渠非恒定流的格子Boltzmann模型。通过对一维溃坝波和二维圆形溃坝波的模拟分析,验证了该模型的有效性。以某水电站尾水渠为例,模拟分析了由机组甩负荷和增负荷引起的水位波动规律,为尾水渠的设计提供了依据。     

珲春市草帽顶子矿泉水评价

草帽顶子矿泉水为偏硅酸矿泉水．含有钴、锶等多种人体必需的微量元素,是一处优质天然矿泉水。起源于大气降水．矿化时间约15年．流量较大,具有重要的开发利用价值．