考虑应力状态的悬挂式防渗墙-砂砾石地基管涌临界坡降试验研究     

罗玉龙  吴强  詹美礼  盛金昌 《岩土力学》2012,33(Z1):73-78

悬挂式防渗墙-强透水地基所处的应力状态,对其管涌等渗透变形发展过程影响明显。利用自行研制的新型土与结构物接触剪切渗透仪,开展不同应力状态下悬挂式防渗墙--缺乏中间级配的管涌型砂砾石地基的渗流-应力耦合管涌试验研究。结果表明,应力状态对悬挂式防渗墙-砂砾石地基的管涌临界渗透坡降影响巨大,围压越大,管涌临界渗透坡降越大,基于试验结果,建立了由围压表示的管涌临界渗透坡降线性经验公式。研究成果体现了渗流-应力耦合效应对防渗墙-砂砾石地基渗透稳定性的影响,可为确定深厚覆盖层中悬挂式防渗墙的合理贯入深度提供重要的理论依据。  相似文献   

关于渗流的力及其应用   总被引：5，自引：1，他引：4  

毛昶熙  段祥宝 《岩土力学》2009,30(6):1569-1574

饱和渗流是岩土体失稳的重要因素。叙述了渗流产生的消极破坏力“浮力”和积极破坏力“渗透力”。较详细地讨论了渗流各力之间的相互转换关系及其在管涌滑坡问题中的正确应用;并特别推荐引用渗透力计算滑坡问题具有简便、精确的优点。并指出了在计算中和设计规范中引用渗流力方面的误解。  相似文献   

基于渗流和管流耦合的管涌数值模拟   总被引：6，自引：0，他引：6  

周晓杰  介玉新  李广信 《岩土力学》2009,30(10):3154-3158

堤坝地基的渗透变形过程实际上是“土中水”转变为“水中土”的过程。在渗透变形发生的集中管涌通道区域,采用常规渗流分析理论,单纯增大管涌通道渗透系数的方法是不太合适的。在未发生渗透变形的区域,用常规渗流理论计算;在管涌通道区域,用管流理论,公共边界上两者之间水头相等、流量大小相等且方向相反,能够较好符合渗透变形的发展规律。为了适应计算过程中内部边界条件不断变化的特点,采用无网格法伽辽金法（element free Galerkin method,EFG）对渗流场进行计算。算例计算表明,这种渗流-管流耦合的方法能够模拟管涌通道绕过防渗墙等复杂的发展过程。  相似文献   

Laboratory soil piping and internal erosion experiments: evaluation of a soil piping model for low‐compacted soils          下载免费PDF全文

Garey A. Fox  Rachel G. Felice  Taber L. Midgley  Glenn V. Wilson  Abdul‐Sahib T. Al‐Madhhachi 《地球表面变化过程与地形》2014,39(9):1137-1145

Mechanistic models have been proposed for soil piping and internal erosion on well‐compacted levees and dams, but limited research has evaluated these models in less compacted (more erodible) soils typical of hillslopes and streambanks. This study utilized a soil box (50 cm long, 50 cm wide and 20 cm tall) to conduct constant‐head, soil pipe and internal erosion experiments for two soils (clay loam from Dry Creek and sandy loam from Cow Creek streambanks) packed at uniform bulk densities. Initial gravimetric moisture contents prior to packing were 10, 12 and 14% for Dry Creek soil and 8, 12, and 14% for Cow Creek soil. A 1‐cm diameter rod was placed horizontally along the length of the soil bed during packing and carefully removed after packing to create a continuous soil pipe. A constant head was maintained at the inflow end. Flow rates and sediment concentrations were measured from the pipe outlet. Replicate submerged jet erosion tests (JETs) were conducted to derive erodibility parameters for repacked samples at the same moisture contents. Flow rates from the box experiments were used to calibrate the mechanistic model. The influence of the initial moisture content was apparent, with some pipes (8% moisture content) expanding so fast that limited data was collected. The mechanistic model was able to estimate equivalent flow rates to those observed in the experiments, but had difficulty matching observed sediment concentrations when the pipes rapidly expanded. The JETs predicted similar erodibility coefficients compared to the mechanistic model for the more erodible cases but not for the less erodible cases (14% moisture content). Improved models are needed that better define the changing soil pipe cross‐section during supply‐ and transport‐limited internal erosion, especially for piping through lower compacted (more erodible) soils as opposed to more well‐compacted soils resulting from constructing levees and dams. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

深基坑承压水的风险控制及处理实例     

徐长节  徐礼阁  孙凤明  於锦  杨迪 《岩土力学》2014,35(Z1):353-358

存在地下承压水的深基坑,当基坑底部承压水层顶部的残留土层不能与承压含水层水头平衡时,处理不当极易造成管涌及坑壁失稳等问题。对相关承压水处理风险源进行分析,针对勘察、设计、施工各阶段都提出具体要求。实例中的基坑临近江面,基坑下承压水与江水存在贯通通道,河道水位变化时会引起承压水头增减,由于设计水头埋深参考值是针对一年观察期而得到的,未考虑到历年水头变化,成为事故埋下隐患,最终因为施工期间河道涨水导致承压水压力超过预期引起了基坑涌水。事故发生后,现场紧急采取堵漏措施,采用灌浆法加固基坑土体,改善土体性质,增加不透水土层的厚度,最终已解决基坑开挖时出现的涌水等现象,保证了工程的顺利安全完成。灌浆法加固是承压水较大情况下基坑安全开挖的有效方式,研究结论对于承压水的风险控制特别是临近江海的工程的设计施工具有较强的指导意义。  相似文献   

Experiment and statistical assessment on piping failures in soils with different gradations     

Kuo-Hsin Yang  Jyun-Yen Wang 《Marine Georesources & Geotechnology》2017,35(4):512-527

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Slope–channel coupling between pipes,gullies and tributary channels in the Mocatán catchment badlands,Southeast Spain     

H. Faulkner  R. Alexander  P. Zukowskyj 《地球表面变化过程与地形》2008,33(8):1242-1260

The dispersive nature of the highly sodic silts of the Triassic‐rich unit of the Góchar formation plays a fundamental role in the erosion of the Mocatán catchment badlands in Almería, where a rejuvenating pipe and incised channel network is rapidly evacuating slope materials. Referring to concepts of medium‐ and long‐term landscape evolution, and incorporating contemporary thoughts on the role of connectivity in system evolution from the geomorphological literature, this paper attempts to develop a conceptual model of the way geologic, topographic, material property and ecological factors combine to explain the complex geomorphological evolution of the site. An electronic distance measurement (EDM) survey was undertaken using a Leica TC3100, to produce a detailed topographic map. This database was supplemented by geomorphological, geological and ecological data derived from ground survey and remote sensing, and further morphometric analysis undertaken. Preferred orientations of channel segments, and the topographic distribution of pipe‐roof‐collapse features and outfalls in relation to known stratigraphic controls, suggests that, once coupled to the slope‐base channel, pipe networks develop in a systematic, sequential way. A wave of incision moving up the main channel reconnects channels with slopes, and the resulting increased hydraulic gradients on sideslopes encourage extensive deep pipe development for the first time in these materials. Once major pipe development is possible, three‐dimensional pipe networks enlarge and then collapse to form an extensive, partially coupled steep‐sided gully network. From this perspective, the coupling of the pipe to a rejuvenating channel is a significant intrinsic threshold event and the main reason that badlands have developed locally in these dispersive materials. It is concluded that erosion in this landscape will only be suppressed after a considerable period of slope‐base stability, which could allow a gradual loss of sodium from the surface by leaching or organic exchanges. Both theoretical and management implications are explored. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Sediment detachment in piping-prone soils: Cohesion sources and potential weakening mechanisms     

Anita Bernatek-Jakiel  Jiří Bruthans  Jan Vojtíšek  Mateusz Stolarczyk  Tomasz Zaleski 《地球表面变化过程与地形》2020,45(13):3185-3201

Soil piping is a widespread land degradation process that may lead to gully formation. However, the processes involved in sediment detachment from soil pipe walls have not been well studied, although their recognition is a crucial step to protect soils from piping erosion. This study aims to recognize the factors affecting cohesion and to identify the mechanisms which are likely to be responsible for the disintegration of soil. The study has been conducted in mid-altitude mountains under a temperate climate (the Bieszczady Mountains, the Carpathians, SE Poland). The research was based on the detailed field and laboratory analyses of morphology, and the physical and chemical properties of soil profiles with and without soil pipes. Moreover, experiments with flooding the undisturbed soil samples using different solutions (deionized water, ammonium oxalate, dithionate citrate, 35% hydrochloric acid and 30% hydrogen peroxide) were conducted in order to check the role of air slaking, the removal of soil organic carbon (SOC), and Fe and Al oxides on sediment detachment. The obtained results have confirmed that soil pipes develop in quite cohesive soils (silt loams), which allow the formation and maintenance of pipes with a diameter up to 30 cm. Soil cohesion, and thus susceptibility to piping, are impacted by the content of major oxides, soil particle size distribution, biological activity and porosity. The tested soils affected by piping erosion have a lower content of Al₂O₃ and Fe₂O₃, and free Fe (Fe_(DCB)), lower clay content, higher biological activity (more roots and animal burrows), higher porosity, and more and larger pores than the profile without soil pipes. The experiments have indicated that especially SOC along with Fe and Al oxides are an important cohesion source in the study area. This suggests that the removal of SOC, and Fe and Al oxides may weaken and disintegrate aggregates in soil pipes. Further study of soil leaching and tensile strength will broaden understanding of which chemical processes control where pipes will develop in other cohesive piping-prone soils. © 2020 John Wiley & Sons, Ltd.  相似文献   

细砂层埋深对堤基管涌影响的试验研究   总被引：1，自引：0，他引：1  

陈建生  袁克龙  王霜  张华  何文政 《岩土力学》2015,36(3):653-659

不同土层结构的堤基,其管涌发生和发展的情形不同。以前的研究多集中于双层堤基的情况。事实上,含夹砂层堤基中,位于砂砾石层内的细砂层会对堤基管涌的发生产生重大影响,并且这些影响随细砂层在砂砾石层中的位置不同而不尽相同。利用室内砂槽试验,模拟当细砂层位于砂砾石层内部不同深度时含夹砂层堤基管涌的发展过程,研究细砂层埋深对 堤基管涌的影响。试验结果表明,细砂层埋深存在一个临界深度,当细砂层埋深较浅时,堤基的临界水力梯度较小,易于发生管涌,且管涌发生以后,堤基被侵蚀的速率较大,出砂较多;堤基破坏的临界水力梯度随着细砂层埋深的增加而增大,当细砂层埋深大于临界埋深时,堤基的临界水力梯度基本不变,同时堤基抵抗管涌破坏的能力较强,其破坏形式与双层堤基 相类似。  相似文献   

气象信息系统雷电综合防护技术的探讨     

谭龙 《气象研究与应用》2003,24(3):53-56

分析了雷电对广西气象台站的气象信息系统造成危害的主要原因,并提出了采用接闪、分流、屏蔽、合理布线、等电位连接、共用接地系统、过电压和过电流电涌防护等进行综合防护的主要措施。  相似文献