Bayes约束随机场下坝基溶蚀区随机模拟方法及其影响分析

基于完全随机场模拟溶蚀岩体可能会高估其空间变异性和不能有效地利用溶蚀以外的地质信息和实践经验,提出用Bayes约束参数随机场模型描述坝基溶蚀区的随机模拟方法。引入Bayes公式,对溶蚀区域岩土参数的统计特性进行修正,反映出地质勘测的新增地质信息和试验参数信息,建立约束随机场,并在此基础上进行随机有限元分析,研究坝基溶蚀对大坝结构性态的作用效应。计算结果表明,相对于完全随机场模型,Bayes约束随机场模型更为客观地考虑了溶蚀岩体的空间变异性,有效地降低了溶蚀参数完全随机场下结构响应的模拟方差。在概率分析过程中,推荐蒙特卡洛响应面耦合方法（MC-RSM）作为适用于复杂工程的随机模拟方法,该方法能够代替直接MC法对同样力学机制的不断重复,减小计算时间成本。     

乌东德高拱坝极限抗震能力研究

乌东德水电站是金沙江下游河段上4个水电梯级的最上游梯级,大坝为265 m高的双曲拱坝。采用非线性有限元法,将拱坝坝体-坝基作为一个整体系统,在考虑坝体横缝影响及无限地基辐射阻尼影响基础上,模拟坝肩控制性滑块各滑裂面在地震作用下张开、滑移的非线性力学行为,研究设计与校核地震作用下大坝的抗震性能,探讨大坝-坝基整体系统在强震作用下的抗震潜力。研究结果表明：设计地震条件下,坝体仅在拱端应力集中区域拉应力超过抗拉强度,压应力则均满足强度要求,坝肩块体稳定,大坝-坝基体系的整体安全性可以保证;校核地震条件下,坝体应力值略有增加,能够满足不溃坝的设防要求;以大坝-坝基代表性的位移、变形量变化曲线的拐点作为评价极限抗震能力的标准,可知拱坝-坝基体系的抗震超载安全系数为2.7,相应的基岩水平向峰值加速度0.729g,拱坝-坝基体系抗剪参数强度储备安全系数为2.0,乌东德高拱坝具备较强的极限抗震能力。     

考虑土石料颗粒破碎和密度变化的次塑性本构模型建模方法

试验和现场观测都发现高土石坝的坝料在高压及湿化作用下会发生显著的颗粒破碎,颗粒破碎会改变土石料的级配曲线和密度,因而影响其后继力学行为,因此,土石料的颗粒破碎是当前岩土工程领域的研究热点。为了模拟土石料在高压及湿化作用下发生显著的颗粒破碎现象,以及循环加载中的颗粒破碎与应力诱导各向异性随动硬化共同影响下土石料的变形,本文提出了一个建模方法,考虑土石料颗粒破碎和密度变化的影响。所建议的次塑性本构模型在经过试验资料的验证后可用于动力有限元数值计算。     

干湿循环作用对堆石长期变形影响的试验研究

堆石体存在流变,不仅与荷载有关,而且与日晒雨淋引起的干湿循环有关。通过室内试验模拟日晒雨淋引起的干湿循环作用,研究其对堆石体长期变形的影响。试验结果表明,荷载作用流变很快趋于稳定,测得的流变量也相对较小;偏应力状态干湿循环作用引起的长期变形非常明显,其变形占后期变形总量的50%~70%,且后期变形的衰减远小于荷载单独作用引起的流变,这对于坝体的安全和稳定的影响是不容忽视的。根据试验研究揭示的变形规律,本文建立了相应的计算干湿循环变形的数值模型,可用于有限元计算。     

Discovery of an ice cave in the Yatude Valley, Langhovde, Dronning Maud Land, East Antarctica

A circular hole was discovered on the downstream side of a glacier dam in the Yatude Valley, Langhovde, East Antarctica, during the 2005–2006 austral summer. The opening of this hole is the first opportunity enabling us to observe the interior of the dam. The opening led to a large cave in the dam, raising the possibility of meltwater drainage through the dam. The Yatude Valley is an approximately U-shaped fluvial valley. The valley floor has been incised to form a box-shaped inner valley that contains fluvial terraces and large boulders upon the valley floor. The origin of these features can be explained by a large amount of running water; however, we consider it unlikely that a regular current has flowed through this site for a long period. Instead, it is more likely that large quantities of lake water have been periodically discharged due to collapse of the glacier dam or spilling out through a tunnel channel within the cave. The discovered hole and the ice cave are key features in understanding the historical development of the Yatude Valley in relation to the melting history of the Antarctic ice sheet.     

重力坝层间抗滑稳定体系的动力可靠度分析方法

受明显的层状结构影响,加之材料参数和动荷载的双重随机性,动力条件下碾压混凝土重力坝的层间抗滑稳定可靠度问题值得关注。考虑地震波频谱特性、峰值加速度、坝体材料参数的随机性,统计概化出地震作用下坝体的潜在滑动失效路径;在特定地震动作用下,基于随机有限元分析结果,采用刚体极限状态判断准则和响应面法构建失效路径的动力抗滑稳定功能函数,进而求得其抗滑稳定可靠指标;接着考虑不同失效路径的相关性,用Ditlevsen窄界限公式估算体系的可靠度;最后,考虑地震动荷载的随机性,采用基于全概率公式的数值拟合积分方法求解大坝抗滑稳定体系的动力可靠度。研究结果表明,动力条件下,当水平地震系数大于0.2时,重力坝层间抗滑体系可靠度不再由建基面失效路径决定,而是由下游折坡处层面的失效路径决定。该方法数学意义明确,实用性强。     

基于流固耦合理论某尾矿坝失稳特性及稳定性分析

选用典型的尾矿库工程实例,采用流固耦合和强度折减法相结合对其尾矿坝进行稳定性分析,确定尾矿库渗流场分布及浸润线的位置,该浸润线位置与实测浸润线位置吻合较好。建议强度折减过程中尾矿坝的失稳准则,计算安全系数,确定潜在滑裂面的位置,并与极限平衡法计算出的安全系数及临界滑裂面位置进行比较,表明强度折减法得出的结果与Bishop法结果接近,流固耦合-强度折减法在尾矿库稳定性分析的可行性。在该基础上研究尾矿坝潜在的失稳模式,将尾矿坝潜在的失稳模式分为局部失稳和整体性失稳两种,局部失稳为尾矿坝的部分坝面发生滑移,整体失稳为整个尾矿坝坝体发生失稳,并分析导致该尾矿坝两种失稳模式的主要因素,认为浸润线埋深过浅是导致局部失稳的主要原因。     

An ‘Effective’ Involvement of Indigenous People in Environmental Impact Assessment: the cultural impact assessment of the Saru River Region,Japan

The Cultural Impact Assessment of the Saru River Region represents the first time that a site investigation was implemented in Japan in order to preserve an ethnic culture in relation to the construction of a dam. One of the project's basic concepts was to get local residents, especially those of Ainu ethnicity, to participate in the investigation. Existing case studies of environmental impact assessment have argued that the assessment has failed to sufficiently involve Indigenous people in its process and has largely failed to incorporate Indigenous knowledge, cultural values, and voices into its processes and outcomes. Also, intangible aspects of Indigenous cultural heritage have not been protected. In the Cultural Impact Assessment of the Saru River Region, the Final Report was released in 2006 and significantly included the 3 year investigation of input by local residents. In this sense, this assessment succeeded in effectively involving Indigenous people in its process and in reflecting their cultural values in its results. The more important issue is, however, how these results were included in the final outcomes. If Indigenous people have no power over final decision making, their involvement is not effective. This paper analyses the significance and unresolved problems involved in this overall assessment process.     

芦山地震冶勒大坝强震监测资料分析

冶勒沥青混凝土心墙堆石坝最大坝高为124.5 m,坝址区地震烈度高,地质条件复杂,两岸坝基条件严重不对称。大坝上布设了9台强震仪组成的强震监测台阵,曾获得2008年汶川地震和攀枝花地震的大坝强震监测记录。2013年4月20日四川省雅安市芦山县发生里氏7.0级地震,冶勒大坝距震中约212.5 km,坝址区震感较为强烈,强震监测台阵获得了此次地震较为完整的有效记录。对芦山地震主震记录进行时域分析和频谱分析,总结冶勒大坝在芦山地震中的动力反应规律,并与汶川地震时坝体动力反应进行对比分析。研究表明,芦山地震主震时冶勒大坝最大加速度记录为47.043 cm/s2,最长持续时间为76.98 s,坝顶动力放大效应明显;芦山和汶川地震时大坝动力反应规律的差异与地震波频谱特性及大坝自振特性等密切相关。总体而言,冶勒大坝在震后运行安全稳定,芦山地震未对冶勒大坝造成明显不利影响。     

Breach of a tailings dam in the 2011 earthquake in Japan

The eastern region of the northern part of Japanese mainland has been known historically as an area of mines producing gold and silver. When the extraordinarily strong earthquake rocked the eastern part of the Japanese mainland on March 11, 2011, there were more than 20 old and new dams retaining tailings from many mines.Out of these, three dams suffered breach due to liquefaction of tailings materials and released a large amount of slime, bringing about damage to farmlands and houses downstream. Of particular interest was Kayakari dam at Ohya mine that failed and Takasega-mori dam in its vicinity that did not, although they were equally subjected to strong shaking.In this paper features of these two dams in the design and construction, and damage or non-damage during the earthquake will be described, together with the geotechnical investigations and some analyses that were conducted after the earthquake.