高烈度地震区细粒尾矿上游法筑坝动力反应与稳定性分析

 核桃箐尾矿库位于中甸-大理地震带,其抗震设防烈度为8度,且入库尾矿为细粒尾矿。为论证其采用上游式工艺进行筑坝的可行性,综合运用堆坝模型试验、土工测试、理论分析和数值模拟等多种方法,对其动力反应与静、动力稳定性进行了系统研究。结果表明,通过高筑初期坝、合理设置排渗设施并增设块石贴坡,可以使核桃箐尾矿库尾矿坝的静、动力稳定性达到规范要求,从理论上证明了通过采取合适的抗震措施,在8度地震区的细粒尾矿库采用上游法筑坝是可行的。研究中还发现,由于动孔隙水压力的产生和增长,尾矿坝的动力安全系数在地震过程中呈波动下降的趋势。较大的永久变形是细粒尾矿堆坝的主要震害形式之一,当干滩面长度和安全超高不足时,震后容易发生漫坝事故。并从细观角度,对细粒尾矿堆坝颗粒分级不明显、浸润线埋深浅、滩面坡度缓等特点的成因进行了分析。     

水库大坝地震后特别检查(英文)

地震可以不同方式对水库大坝造成破坏:①强烈的地振动;②坝基沿断层或其他间断面的位移;③水库内断层活动引起波浪使大坝失去超高;④岩体向水库运动形成冲击波。大地震影响的范围较广,可能影响的水库大坝数量也较多,如2001年发生的印度Bhuj地震,有240多座水库大坝(主要为小型的土石坝)因遭受破坏而需要除险加固。另外,2008年5月12日发生在四川汶川的8级地震,有1580多座水库大坝遭受到不同程度的破坏。2008年6月14日日本Iwate-Miyagi Nairiku7.2级地震发生后,对其涉及的134座水库大坝进行了地震后特别检查。通常,负责大坝安全的部门需要通过调查对震损水库的安全状况进行评估,进行调查时最好使用检查表。2008年国际大坝委员会对使用了20a的地震后水坝检查导则进行了全面修订,其中包括土石坝及混凝土坝的震后检查表。介绍了导则修改后的特点,并希望提供的检查表不仅应用于水库大坝的震后检查,也可应用于水库大坝一般检查。     

Modified risk assessment tool for embankment dams: case study of three dams in Turkey

Dam failures are catastrophic accidents resulting in property damage and loss of life. Risk prioritisation systems should be used in accordance with dam safety regulations to prevent these disasters. The purpose of this paper is to develop a risk assessment software which can be used by the decision makers for ranking of dams. Risk assessment was conducted on three embankment dams from Turkey to obtain information about the dam performance based on piping, earthquake, normal stability and flood failure modes. Parameters are incorporated into the programme to develop a new model that could predict variables such as breach width, dam failure time, side slope and peak breach discharge. The proposed tool gives flexibility to choose dam elements for describing the primary features of the evaluated dam; so users can make hazard categorisation of dams according to their risk level which is based on unique project conditions.     

Numerical simulation of damage in high arch dam due to earthquake

Based on the assumption that concrete is macroscopic homogeneous, the cracking evolution process and damage mode of high arch dams are studied in consideration of the heterogeneity of concrete in mesoscale. The bilinear damage evolution model and the damage evolution model expressed in power function with descending section are adopted to combine with the Mohr-Coulomb criterion to investigate the crack development and fracture mode of high arch dams under the action of an earthquake. The analysis result of a high arch dam in China under design shows that cracks that take place in concrete are caused by excessive tensile stress. The cracks initiate at the middle of the dam top and distribute at the upper half of the dam while the rest of the parts remain intact. This conclusion agrees with the model test result.     

高土石坝地震安全控制标准与极限抗震能力研究

基于土石坝震害调查和原型观测资料分析，针对高土石坝的坝坡稳定、坝体地震永久变形以及混凝土面板接缝位移3个影响高土石坝安全的主要因素，初步建议了相应的地震安全控制标准，并应用于高心墙堆石坝和面板堆石坝的极限抗震能力计算分析。结果表明：按规范设计的高土石坝具有较强的抗震能力，其极限抗震能力在0.50g以上，可抵抗9度以上地震而不致于出现灾难性后果；高土石坝的极限抗震能力与相应的地震安全控制标准密切相关，按照本文建议的标准，高心墙堆石坝坝坡稳定是其极限抗震能力的控制因素，高面板堆石坝面板周边缝安全是其极限抗震能力的控制因素。     

爆炸液化场地上堤坝变形的模型试验研究

饱和砂土地基在地震、爆炸等振动荷载作用下易发生液化,从而使堤坝等上部构筑物发生破坏。开展了爆炸液化场地上堤坝变形的大型模型试验,考虑了筑坝材料以及堤坝地基加固措施对堤坝变形和坝身裂缝的影响。试验表明:堤坝沉降主要发生在场地液化后的1~2 h内,该段时间内产生的沉降占7 d时沉降量的84%~87%;掺加了碎石的堤坝比未加碎石的堤坝7 d时沉降量大24%;地基内采用土工格栅+土工布的加固措施能够有效减少堤坝在液化场地上的沉降,比未加固的堤坝沉降减少了10%。堤坝的裂缝主要出现在细骨料筑成的坝段和不同筑坝材料的交界处,沿坝身开展。总结了国内外规范中对于液化地基沉降的计算及预测方法,根据液化地基上浅基础建筑物沉降图表对试验中的堤坝沉降进行了推算,发现实测沉降与推算沉降比较接近。     

汶川8.0级地震对典型高坝结构安全的影响分析

 汶川8.0级地震具有震级高、震源浅、破坏性强和次生地质灾害严重等特点。在对震区高坝灾情归类分析的基础上,选择典型的不同坝型高坝,包括宝珠寺重力坝、沙牌碾压混凝土拱坝、紫坪铺面板堆石坝等工程,从大坝距发震断裂距离、大坝基础处理及大坝结构类型的抗震性等因素对大坝结构安全的影响展开分析研究。结合在建的一批300 m级高坝,对抗震设防标准、水库诱发地震等问题进行讨论。结果表明：(1) 现行大坝抗震设计是可行的,300 m级高坝工程抗震能力仍需深化研究;(2) 大坝工程基础、抗力体经合理加固后,增强了岩体结构的整体性,可有效提高大坝及基础的抗震能力;(3) 高坝应急预案的设计与管理,流域性统一公共水电工程灾害应急平台建设有待加强;(4) 对水库诱发地震的研究需加强。     

Performance of a Fill dam Based on the Performance-Based Design Concept and Study of a Seismic Retrofitting Method

Fill dams have long been designed by conventional specification based design methods which stipulate details concerning dam body materials, structural calculation methods, and construction methods. There are irrational aspects to applying the specification based design method to a case subjected to large earthquake such as the 1995 Hyogo-ken Nanbu Earthquake, a type that rarely occurs. Thus, since the Hyogo-ken Nanbu Earthquake, the concept of performance-based design that treats performance of a structure as the only requirement has been incorporated, and conventional specification-based design is now being replaced by performance-based design based on required performance as the design method for structures. When an earthquake strikes a fill dam, water in the dam must not overflow the dam body causing a severe disaster in the area downstream from the dam. It is, therefore, necessary that settlement at a dam crest during an earthquake does not exceed a critical value, requiring that it be designed by an analysis method capable of accurately predicting the quantity of settlement produced. This report describes a design study of a fill dam, which requires a high level of seismic performance because of its location conditions and functions. Performed by applying the concept of ISO23469 to an existing fill dam, the study focused on ① setting performance criteria, ② evaluating safety of a fill dam during an earthquake, and ③ reinforcement method that satisfies the performance criteria and evaluation of its safety.     

地震作用下土坝抗裂稳定性的判别

调查表明,土石坝常见的震害形式是平行坝轴线的裂缝。文中通过一系列模型坝的实验,研究了裂缝形成的条件。利用迈勒累积损伤模型和随机振动理论提出了估价土坝在地震作用下抗裂性能的计算公式,并据此研究了一座实际土坝出现地震裂缝的可能性。     

关于可靠度理论应用于混凝土坝设计的问题

水荷载和自重可作为定值考虑,没有必要按随机变量处理,渗透压力、温度、地震等荷载,确有较大变异性,但问题较复杂,很难确定它们的统计参数。机口取样的混凝土强度试验资料较多,但混凝土的平仓振捣、冷缝、裂缝等因素,对坝体抗力的影响更大,而对于这些因素,可靠度理论是无能为力的。对混凝土坝安全影响最大的是基础内部的软弱结构面,由于埋藏地下,仅靠钻孔和少量探硐资料,很难用可靠度理论进行分析。混凝土坝设计以采用总安全系数为宜,安全系数的取值,主要依靠长期以来国内外实际工程的经验,而不是可靠度理论。     

Numerical simulation of damage in high arch dam due to earthquake

Based on the assumption that concrete is macroscopic homogeneous, the cracking evolution process and damage mode of high arch dams are studied in consideration of the heterogeneity of concrete in mesoscale. The bilinear damage evolution model and the damage evolution model expressed in power function with descending section are adopted to combine with the Mohr-Coulomb criterion with tension cut-off to investigate the crack development and fracture mode of high arch dams under the action of an earthquake. The analysis result of a high arch dam in China under design shows that cracks that take place in concrete are caused by excessive tensile stress. The cracks initiate at the middle of the dam top and distribute at the upper half of the dam while the rest of the parts remain intact. This conclusion agrees with the model test result. __________ Translated from Shuili Xuebao, 2008, 39(7): 848–853 [译自: 水利学报]     

Evaluation of seismic hazard,local site effect,liquefaction potential,and dynamic performance of a world example of an embankment dam characterized by very complex and unique foundations conditions: Karameh dam in the Jordan Valley

The geologic structures associated with the site of a 55·10⁶ m³ Karameh embankment dam (under construction in Jordan Valley) and the tectonic effects on dam foundation and reservoir margins were reviewed. The regional seismicity and history of events were analyzed and a design earthquake was established. At Karameh dam site, the geotechnical conditions for the foundations formations (including liquefiable sands) and materials to be placed, the presence of the major Jordan Valley fault crossing the site, the hydrogeological conditions with salty artesian aquifers and soluble soils make this site a unique, very complex one at the limit of feasibility. The under construction Karameh dam is situated in the Dead Sea Rift (32.00°N, 35.50°E), the boundary between the Arabian and African-Sinai plates. The primary seismic source contributing to the hazard at the Karameh dam site is the active Jordan Valley fault which extends from the Dead Sea to the Sea of Galilee with an expected maximum earthquake magnitude of 7.8, and passes under the right abutment of the dam body. A probabilistic method is used to evaluate the seismic hazard at the dam site. The Peak Ground Acceleration (PGA) is selected as a measure of ground motion severity. Analysis is carried out for 50%, 90% and 95% probability that is not being exceeded in a life time of 50, 100, and 200 years. According to guidelines of ICOLD, PGA for a Maximum Design Earthquake (MDE) was 0.50 g and for an Operating Basis Earthquake (OBE) it was 0.17 g. Local site effect analysis was carried out using the computer code SHAKE (Schnabelet al., 1972). The performance of the dam under dynamic loading was analyzed. The factor of safety was evaluated for different cases of dam operation. Newmark sliding block on a plane method was used to evaluate the displacement of the dam body considering liquefaction potential. A PGA of 0.50 g associated with the MDE will trigger liquefaction of the sand layers existing in the dam foundation. Similarly, liquefaction may occur in the dam foundation layers in case of 7.8 magnitude earthquake which is expected to result in a crest settlement of 4.4 m. The event horizontal rupture displacement for an earthquake of this magnitude will be about 12 m. To safely resist large earthquake events, it is recommended to have the following safety measures for the design of the dam: (1) free board should be increase at least to 7.0 m instead of the 5.0 m of the final design; (2) the foundation of the dam should be stabilized against liquefaction hazard; and (3) the embankment internal zoning should be designed to accomodate damage resulting from earthquakes of intensity greater than the OBE event. Critical elements of the embakment regarding safety are the core, downstream fine filter, chimney drain and drainage blanket. The downstream critical filter zone had a horizontal width of 5.0 m, enhanced to 7.0 m in the vicinity of the main fault. Stability analysis indicated that embankment side slopes as flat as 1(V):8(H) were required.     

堰塞湖坝体动力特性及加速度分布规律大型振动台模型试验研究

 2008年汶川八级地震形成了至少257个堰塞坝,主震后发生的大量余震可能会影响堰塞坝的动力安全状态。堰塞坝体的动力特性参数(包括自振频率和阻尼比等)和加速度分布规律是堰塞坝地震安全研究的基础内容。通过大型振动台模型试验,研究在余震作用下模型堰塞坝体的动力特性参数、加速度分布规律及二者的影响因素,并根据动力相似律,计算原型坝体的动力特性参数。共进行2组不同材料的振动台模型试验,分别模拟含黏粒较多且颗粒较小(坝体I)和基本不含黏粒且颗粒较大(坝体II)的2种坝体。在不同地震波形输入、不同加速度峰值和不同水位条件下进行振动台试验。研究成果表明：(1) 模型坝体具有较稳定的X向和Z向自振频率和阻尼比。(2) 先期振动使坝体自振频率降低,阻尼比有增大趋势;坝体I的自振频率小于坝体II。水位变化对2种坝体自振频率的影响规律不一致。(3) 加速度放大倍数随高程增大而增大,最大加速度发生在坝顶处;相同高程测点加速度放大倍数最大值出现在上游或下游靠近坝坡表面处,即“表面放大”效应明显,说明坝坡表面容易受地震作用破坏。(4) 所含频谱成分与坝体自振频率接近的地震波会引起最大的加速度反应。Z向振动使坝体测点X向加速度放大倍数增大。加速度放大倍数一般随输入加速度峰值的增大而减小。     

新疆坝工技术进展

新疆有大小河流570余条,97%的河川径流形成于山区。因此,山区水库大坝建设是开发水能资源、实现水资源合理配置与有效调控的重要措施。自20世纪90年代以来,新疆的水库建设已从平原水库转入山区水库建设,筑坝材料也在当地材料坝的基础上不断改进,碾压混凝土坝、混凝土面板砂砾石堆石坝、沥青混凝土心墙堆石坝、土工膜防渗堆石坝等坝型不断涌现。结合新疆坝工建设,系统地总结了坝工技术特点和取得的主要技术创新成果,研究认为:以黏土心墙堆石坝为基础坝型,以混凝土面板砂砾石堆石坝和沥青混凝土心墙堆石坝为主要发展方向,在高寒地区、高地震区、深厚覆盖层等特殊环境和各种不良地质条件下的筑坝技术,是新疆坝工建设的显著特点。努力在坝工设计、坝基处理、施工工艺和建筑材料等关键技术取得不断进步和创新,对于提高大坝建设和运行管理的技术经济水平、安全可靠性能具有非常重要的促进作用。     

小型水坝的地震安全(英文)

大多数用于灌溉和供水的坝为高度小于 15 m 的土坝,并称之为乡村坝。国际大坝委员会所辖大坝的坝高都在15 m 以上,这些小型水坝并不在委员会管辖范围之内。通常,乡村坝由地方社区或水坝工程建设经验不足的组织资助修建起来的,印度尤其如此。例如 1 月 26 日发生在印度古茶拉底省的 Bhuj 地震,波及到 240 座水坝。显然这些坝的质量远比不上水电站大坝的质量,然而小型水坝的事故将会影响到整个大坝行业的前景,所以这些乡村水坝也应该满足基本的设计与安全准则,以免对整个大坝行业造成负面影响。     

Assessment of the safety of earth dams

The assessment of safety of earth dams based on the results of preliminary inspections is analyzed by fuzzy calculus. Fuzzy sets are used to represent the engineer's judgement on the seriousness (gravity) of observed defects and their relation to dam dafety. Two analytical models are proposed and applied to three earth dams exhibiting different types of defects. The results of the calculations are compared with the engineer's recommendations.     

Coquitlam大坝抗震能力提高设计(英文)

Coquitlam 大坝建于 1913 年,坝高 30 m,为吹填土石坝。大坝位于加拿大 BC 省高地震危险带。风险人口数以万计。根据现行标准,大坝的抗震能力不符合要求,坝体冲填土和某些部位地基土松散,容易液化。在中度至重度的地震情况下,大坝将会遭受严重的损坏,并有可能溃决。提高大坝的抗震能力很有必要。选择最高设计地震为里氏7.5 级地震,地震地面水平峰值加速度 0.66g。在设计中,还需要对以下一些提高抗震能力的设计方案进行评估,包括结构修复、大坝重建、限制水库运行及退役。在综合考虑技术、社会、环境和经济因素的基础上,选择了兴建一座新的下游堤坝以提高其抗震能力,减少 Coquitlam 大坝的地震风险。新建坝包括一座土质心墙堆石堤坝和一个位于左坝肩的混凝土过渡带。新建堤坝大部分是建在具有承载力的淤泥土上,而混凝土过渡带则完全建在基岩上。由于现场和施工条件的限制,座落在现有大坝下游坝壳部分的新建堤坝上游坡的下部一小部分为沿原河道的液化砂砾石冲积层。先进的地震稳定性和变形分析结果表明,由于有足够的超高、厚厚的反滤体以及过渡带,大坝所产生的变形是可以接受的。为了控制基础渗流和出逸坡降,设计采用了塑性混凝土防渗墙、帷幕灌浆以及在下游增设一套减压井相结合的方案。为了监测新建坝的性态,在施工期和运行期的仪器监测设计中采用了基于破坏模式的方法。主要介绍了 Coquitlam新建堤坝的设计,包括大坝安全监测系统的设计。     

Features of seismic hazard in large dam projects and strong motion monitoring of large dams

Earthquakes can affect large dam projects in many different ways. Usually, design engineers are focussing on ground shaking and neglect the other aspects. The May 12, 2008 Wenchuan earthquake has damaged 1803 dams and reservoirs, and 403 hydropower plants with an installed capacity of 3.3GW. Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam. These recently completed dams are dam types which, up to now, have not experienced strong ground shaking. The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan. The different features of earthquake hazard are presented, i.e., ground shaking, faulting and mass movements. It is proposed to prepare project-specific safety plans for all dams, which consist of a matrix where the possible hazards and the corresponding countermeasures are listed. The earthquake behaviors of the Sefid Rud, Zipingpu and Shapai dams, which, in the past, have experienced strong ground shaking from nearby earthquakes, are discussed. Finally, the need for strong motion instrumentation of large dams is discussed. It is proposed that major dams with large damage potential, dams located in areas of high seismicity, and dams showing signs of abnormal behavior be equipped with strong motion instruments.     

Features of seismic hazard in large dam projects and strong motion monitoring of large dams

Earthquakes can affect large dam projects in many different ways. Usually, design engineers are focussing on ground shaking and neglect the other aspects. The May 12, 2008 Wenchuan earthquake has damaged 1803 dams and reservoirs, and 403 hydropower plants with an installed capacity of 3.3GW. Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam. These recently completed dams are dam types which, up to now, have not experienced strong ground shaking. The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan. The different features of earthquake hazard are presented, i.e., ground shaking, faulting and mass movements. It is proposed to prepare project-specific safety plans for all dams, which consist of a matrix where the possible hazards and the corresponding countermeasures are listed. The earthquake behaviors of the Sefid Rud, Zipingpu and Shapai dams, which, in the past, have experienced strong ground shaking from nearby earthquakes, are discussed. Finally, the need for strong motion instrumentation of large dams is discussed. It is proposed that major dams with large damage potential, dams located in areas of high seismicity, and dams showing signs of abnormal behavior be equipped with strong motion instruments.     

Evaluation of the dynamic response of the Damlapinar CFR dam

Concrete faced rock-fill (CFR) dams are now very popular. The structural complexity of these dams and the high risk associated with the social and environmental consequences of failures require very reliable analyses of their performance, especially as regards seismic loading. In this paper, a dynamic analysis procedure for CFR dams is proposed and described, using the Damlapınar CFR dam as a case study. The acceleration time history and maximum horizontal peak ground acceleration values were developed based on maximum credible earthquakes over 50 years from nearby seismic sources. Numerical studies showed that the Damlapınar CFR dam will remain stable under the maximum credible earthquake with a peak ground acceleration of 0.15 g. According to the numerical results, earthquake-induced deformations of the dam are expected to be within the safety margins determined by the Ministry of Public Works and Settlement, Turkey. The results also indicate that a non-linear analysis capable of capturing dominant non-linear mechanisms can be used to assess the stability of CFR dams.