Deep-seated., complex tunnel systems — a hydrological study in a semi-arid catchment, Loess Plateau, China     

T. X. Zhu   《Geomorphology》1997,20(3-4)

During 1989–1990, delailed monitoring of deep-seated, complex tunnel systems was conducted in Yangdaogou, a subbasin in the Hilly Loess Region, Shanxi, which has a catchment area of 0.203 km². It was found that tunnel flow hydrological processes were characterized by a quick response to rainfall, an early flow peak, and a short duration. All the tunnel discharge was derived from overland flow entering via inlets. However, discharge is not significantly related to rainfall parameters in some tunnels, which is contrary to observations on surface plots. Field surveys show frequent blockages of tunnels caused by collapses inside the tunnels which could be reopened in subsequent events, as well as the occasional abrupt opening of new inlets. As a result, tunnel discharge was highly erratic in some of the monitored events. Partial damming within the tunnel systems may also be involved. Hence, instability in the tunnel systems is one of the key factors affecting their hydrologic response. During the period of monitoring, fifteen events occurred and on average at least 43% (ranging from 0 to 78%) of the total basin water discharge was routed through four major tunnel systems which account for 90% of the catchment area of all tunnel systems in the basin. The deep-seated tunnel systems in this area seem not to be developed from the micro-pipes close to the surface. Instead, they are most likely formed in some catastrophic storms and expanded in subsequent storms. 1997 Elsevier Science B.V.  相似文献   

Sinkholes formed by piping into buried channels     

Charles G. Higgins  Carl Schoner 《Geomorphology》1997,20(3-4)

Piping-induced sinks in flood-irrigated alfalfa fields on the distal part of a compound alluvial fan in California's Central Valley lack discharge conduits. It is suggested that all inflow and sediment are dispersed underground in former distributary channels that are now buried.  相似文献   

Design of bentonite/crushed rock seals     

S. Ouyang  J. J. K. Daemen 《Geotechnical and Geological Engineering》1991,9(1):63-72

Summary The use of bentonite/crushed rock mixtures to form hydraulic barriers has greatly increased in recent years. To obtain an appropriate composition for such mixture sealants generally requires extensive laboratory work. Bentonite content and gradation of the crushed rock component are two key parameters in the seal design. This study investigates the effect of crushed rock gradation on the bulk porosity and permeability of systems of crushed tuff particles. Five different gradations are selected from the literature. The bulk porosity of systems of crushed tuff in the presence of bentonite is examined. The Fuller-Thompson gradations yield denser particle arrangements. For mixture samples containing 15% bentonite by weight, the amount of clay accounts for only 45 to 56% of the weight required to fill the interparticle pore space. The bentonite occupancy percentage amounts to 65 to 80% and 75 to 86.5% for samples having 25 and 35% bentonite by weight, respectively. The water content of bentonite at saturation is reduced and the resistance to piping and flow of bentonite is enhanced by the addition of clay. To reduce the bulk porosities of the mixtures containing 25% or more bentonite, a compaction energy higher than the standard Proctor compaction is necessary.  相似文献   

钻孔引发基坑管涌事故的分析与处理对策          下载免费PDF全文

虞利军  陶灵聪  苏华 《探矿工程》2016,43(9):72-74

地下室开挖与基础施工过程中,当坑底存在承压水,如设计考虑不周或施工方法不当,因钻孔穿透承压含水层等原因,将导致管涌发生。结合浙江宁波某基坑管涌处理工程实例,提出采用钢套管、高压旋喷桩、双液注浆的综合处理技术,实践证明,提出的技术可以有效处理类似事故。  相似文献   

Structural,dynamic and anthropic conditions that trigger the emergence of the levee effect: insight from a simplified risk-based framework     

Claudia D’Angelo  Aldo Fiori 《水文科学杂志》2020,65(6):914-927

ABSTRACT

Levees are the most common structural solution to prevent flooding, reduce damage and generate benefits through more investment/economic activity in floodplain areas. While being relatively easy to build, levee effectiveness can be compromised by poor design and substandard construction methods and maintenance, thus increasing failure probability. Further, levees might increase societal vulnerability by instilling a sense of safety, the so-called “levee effect”. To cope with these phenomena, we develop a risk-based framework that quantifies residual risk under levee breaching and the levee effect, by disentangling its structural, dynamic and anthropic components, thus contributing to a better understanding of the phenomena at different spatial scales and the definition of flood risk policies. Through an illustrative example, we show how residual risk might become larger than under natural conditions, as function of the scale of interest, e.g. an area, a line at a given distance from the river, or a point within the floodplain.  相似文献   

君临闽江静压预应力管桩的施工方法及质量控制     

黄金灿 《福建地质》2003,22(4):195-198

福州“君临闽江”桩基工程采用预应力混凝土管桩施工的方法及其质量控制。  相似文献   

基于RBF神经网络的堤防管涌预测方法     

陈亮赵正信  陈建生崔华清 《探矿工程》2007,34(11):5-8

影响堤防管涌的各种因素是不确定和随机的,在堤防管涌的发生过程中各因素间表现出复杂的非线性行为。运用基于RBF神经网络的基本原理,建立了堤防管涌预测的RBF神经网络模型,从新的角度研究堤防管涌的预测问题,对该问题进行了探索性的研究。对该理论的建立以及预测方法进行了系统的讨论,为该领域的研究提供了完整的技术方法。对于23个典型堤防管涌实例的研究表明,RBF网络较BP网络有较高的预测精度,较短的预测时间和较快的预测速度,能够较好地描述堤防管涌的非线性特征。  相似文献   

渗透破坏若干问题的解析解及机理分析     

周健  姚志雄  江建洪 《岩土力学》2006,27(Z2):55-60

讨论了柱坐标下不同介质有限区域内用分离变量法求解Laplace 方程的问题。通过一系列计算试验,给出了柱坐标下Laplace 方程在不同介质有限区域内用分离变量方法求的解,并用该解对渗透破坏现象进行了讨论和实例验证。认为渗透系数分布不均匀是发生渗透破坏的根本原因,渗透破坏朝着渗透系数差异较大的方向发展,并对管涌的复杂机理进行了引申阐述。该工作对于流土、管涌机理的更深入研究具有重要的意义。  相似文献   

无粘性管涌型土的判定   总被引：6，自引：1，他引：5  

刘忠玉  苗天德 《岩土力学》2004,25(7):1072-1076

按照在渗流作用下无粘性土颗粒移动的难易程度,可将其颗粒分为骨架颗粒、阻塞颗粒和可动颗粒三类。如果土体中存在较多的可动颗粒,该土体就可能发生管涌。据此,提出一个判定土体是否可能发生管涌的新方法,可以同时考虑土体的颗粒级配和密实度的影响。通过关管涌实验,证实了该方法的有效性。在此基础上,进一步探讨了土体的密实度对骨架孔隙的最小孔径、界限粒径、可动颗粒含量和阻塞颗粒含量的影响。  相似文献   

软土地区深基坑管涌事故原因分析          下载免费PDF全文

陈华明 《探矿工程》2012,39(2):67-69

通过现场踏勘、数据的采集和工地现场工人的取证,并组织当地专家进行事故调查会议,综合各方面的资料,分析了绍兴软土地区某深基坑围护工程发生基坑管涌事故的原因。为避免今后在粉土、砂土层等软土地区进行深基坑围护工程施工出现类似事故提供经验与借鉴。  相似文献