Validating the ability of the discontinuous deformation analysis method to model normal P‐wave propagation across rock fractures          下载免费PDF全文

Wenjun Gong  Yunsheng Wang  Youjun Ning  Yonghong Luo  Yujie Wang 《国际地质力学数值与分析法杂志》2017,41(10):1267-1282

The effects of fractures on wave propagation problems are increasingly abstracting the attention of scholars and engineers in rock engineering field. This study aims to fully validate the ability of discontinuous deformation analysis (DDA) to model normal P‐wave propagation across rock fractures. The effects of a single fracture and multiple parallel fractures are all tested. The results indicate that DDA can accurately reflect the fracture effects, including the fractures stiffness, the fracture spacing and the fracture number, and the effects of incident wave frequency on one‐dimensional P‐wave propagation problems. Thus, DDA is able to deal well with normal incident P‐wave propagation problems. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Watershed delineation using hydrographic features and a DEM in plain river network region          下载免费PDF全文

Zhengqing Lai  Shuo Li  Guonian Lv  Zhirong Pan  Guosong Fei 《水文研究》2016,30(2):276-288

Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight‐neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector‐based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi‐direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the ‘stream burning’ approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Discrete element model for crack propagation in brittle materials          下载免费PDF全文

Ba Danh Le  Georg Koval  Cyrille Chazallon 《国际地质力学数值与分析法杂志》2016,40(4):583-595

We propose a discrete element model for brittle rupture. The material consists of a bidimensional set of closed‐packed particles in contact. We explore the isotropic elastic behavior of this regular structure to derive a rupture criterion compatible to continuum mechanics. We introduce a classical criterion of mixed mode crack propagation based on the value of the stress intensity factors, obtained by the analysis of two adjacent contacts near a crack tip. Hence, the toughness becomes a direct parameter of the model, without any calibration procedure. We verify the consistency of the formulation as well as its convergence by comparison with theoretical solutions of tensile cracks, a pre‐cracked beam, and an inclined crack under biaxial stress. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Modeling 3D thermal fracture propagation by transient cooling using virtual multidimensional internal bonds          下载免费PDF全文

K. Huang  A. Ghassemi 《国际地质力学数值与分析法杂志》2016,40(17):2293-2311

Thermal fracturing can play an important role in development of unconventional petroleum and geothermal resources. Thermal fractures can result from the nonlinear deformation of the rock in response to thermal stress related to cold water injection as well as heating. Before the rock reaches the final failure stage, material softening and bulk modulus degradation can cause changes in the thermo‐mechanical properties of the solid. In order to capture this aspect of the rock fracture, a virtual multidimensional internal bond‐based thermo‐mechanical model is derived to track elastic, softening, and the failure stages of the rock in response to the temporal changes of its temperature field. The variations in thermo‐mechanical properties of the rock are derived from a nonlinear constitutive model. To represent the thermo‐mechanical behavior of pre‐existing fractures, the element partition method is employed. Using the model, numerical simulation of 3D thermal fracture propagation in brittle rock is carried out. Results of numerical simulations provide evidence of model verification and illustrate nonlinear thermal response and fracture development in rock under uniform cooling. In addition, fracture coalescence in a cluster of fractures under thermal stress is illustrated, and the process of thermal fracturing from a wellbore is captured. Results underscore the importance of thermal stress in reservoir stimulation and show the effectiveness of the model to predict 3D thermal fracturing. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

高山峡谷场地地震动水平峰值加速度传播特性研究     

张玉敏  李幻  朱泽奇 《世界地震工程》2011,27(3)

建立了高山峡谷场地的动力计算模型,分析了攀枝花地震动作用下场地水平峰值加速度(HPA)的衰减效应,研究了不同参数对场地HPA传播特性的影响。数值分析结果表明:HPA随深度增加而衰减,HPA在坡脚处比在峡谷处要低一些;在山顶处有放大效应,但放大系数比实际震害要小一些;HPA衰减程度随着阻尼比和模型深度的增加而增加,随着坡比增加而减小,且不受输入地震动峰值加速度影响;在不同频谱特性地震动作用下,当地震波的卓越频率接近计算模型的自振频率时,场地衰减程度会随之增大。  相似文献   

东海内陆架EC2005孔沉积物粒度分形特征   总被引：1，自引：0，他引：1       下载免费PDF全文

徐方建  李安春  李铁刚  陈世悦  邱隆伟  操应长  林承焰 《地质学报》2011,85(6):1038-1044

对位于浙-闽沿岸泥质带的EC2005孔沉积物粒度分形特征以及与平均粒径和分选系数的关系进行了探讨.EC2005孔沉积物粒度在累积含量5%～95%的无标度区间内,统计自相似程度高,具有分形特征.沉积物平均粒径与分维值既存在正相关,也有负相关关系.二者正、负相关关系的分界点表现为平均粒径7.0φ左右,＜7.0φ时,平均粒径...  相似文献   

岔路口特大型钼多金属矿床的发现及其意义   总被引：4，自引：3，他引：1  

刘翼飞  聂凤军  孙振江  吕克鹏  张可  刘勇 《矿床地质》2011,30(4):759-764

黑龙江岔路口矿床是近年来在大兴安岭地区北部找到的一处特大型斑岩钼多金属矿床,其产出规模已居中国北方钼多金属矿床之首.钼多金属矿化大部分在侏罗系火山-沉积岩中,呈细脉状、细脉浸染状产出,并与晚侏罗世石英斑岩、花岗斑岩和隐爆角砾岩具有密切的时空分布关系.初步研究表明,该矿床无论是在产出环境、地质特征上,还是在含矿侵入岩岩石...  相似文献   

滇东南老寨湾金矿地质特征及成因探讨   总被引：2，自引：0，他引：2  

王明聪 《地质与勘探》2011,47(2):261-267

老寨湾金矿位于云南省东南部,地处著名的"滇黔桂金三角"内,是云南迄今为止唯一进行详查并大规模开发的"卡林型"金矿.现已探明矿床规模为中大型,目前,矿山已建成云南省首座吨金矿山,具有良好的成矿条件和找矿前景.本文通过对矿区地质背景、地质特征、地球化学特征、矿石特征进行了分析,推断矿床成因为后期热液改造形成,属沉积型后期热...  相似文献   

诸广山南部白云岩体岩石地球化学特征及成因     

张善果  黄国龙  沈渭洲  伏顺成  王小冬  许丽丽 《铀矿地质》2011,(5):265-273,281

白云岩体位于诸广山南部岩体中东部,是一个重要的产铀岩体,其岩性为粗粒斑状黑云母花岗岩。在主量元素方面,该岩体的岩石富硅（SiO2平均为73.47%）、富铝（A/CNK值平均为1.09）和高的K2O/Na2O值（平均为1.99）;在微量元素方面,富集大离子元素Rb、Th,而Ba、Sr、Ti、Nb、Ta、P亏损明显,具有高的Rb/Sr（平均为6.22）和Rb/Nb值（平均为29.07）,富含铀（平均为9.04×10-6）,可为岩体内铀矿床的形成提供铀源;轻稀土元素富集和轻、重稀土元素分馏相对明显,稀土元素配分曲线呈右倾型,Eu亏损明显;在同位素方面,εNd（t）值低（平均为-10.6）,（87Sr/86Sr）i值高（平均为0.71688）,Nd模式年龄古老（1865～1874 Ma）。这些特征表明,白云岩体属于典型的壳源型花岗岩,是在华南地块和印支地块碰撞结束后不久形成的伸展构造环境中,位于地壳中-下部的古-中元古代地壳组分在伸展、减薄作用产生的减压、导水和地幔上涌等因素的综合影响下,由泥质岩源区发生部分熔融而形成。  相似文献   

不同地质背景地热系统水-岩作用下温泉水的地球化学特征——以重庆市温塘峡背斜温泉、滇东小江断裂带温泉为例   总被引：1，自引：1，他引：0  

杨雷  肖琼  沈立成  伍坤宇 《中国岩溶》2011,30(2):209-215

本文以重庆市温塘峡背斜和滇东小江断裂带出露温泉为例,探讨了其水文地球化学特征的差异。研究发现,由于地质背景条件基本相同,温塘峡背斜出露的温泉水文地球化学特征比较接近,水化学类型为SO4-Ca（Mg）型,而小江断裂带温泉水文地球化学特征差异较大,泉水水化学类型主要有HCO3-Na型（YN1）、HCO3-Ca型（YN2）、SO4-Ca（Mg）型（YN3和YN5）和SO4-HCO3-Ca-Na型（YN4）,这与各泉点所处地质背景条件不同有很大关系。此外,通过对Na-K-Mg和Na-K-Mg-Ca图解模型的解读得出,所有样品均未达到水-岩平衡,仅有YN1泉点样品接近完全平衡线,表明YN1接近水-岩作用平衡状态,并由上述图解模型估算得到YN1点热储温度大概为100~120℃,与运用SiO2温标计算的热储温度（133~139℃）相差不大。此外,水化学特征和Na-K-Mg-Ca图解分析也表明,YN2与温塘峡背斜温泉水-岩作用过程比较相似。  相似文献