基于广义塑性理论的土工格栅加筋高土石坝的动力分析

Reasonably seismic design methods and aseismic measures are proposed according to the damage characteristics and failure mechanism of structure, and to study the anti- seismic mechanism of the corresponding measures, which is a key problem and objective in seismic research of high earth-rockfill dam.Using large-scale triaxial tests,direct shear tests and the nonlinear finite difference numerical simulation,the project studies the action mechanism and reinforcement effect of geogrid reinforced. The static model, dynamic model and pull model of geogrid reinforced rockfill are established. Based on the generalized plasticity theory and experimental results,the composite calculation method and the separate calculation method are created. Considering the dynamic response of high earth-rockfill dam, a elasto-plastic dynamic analysis method for the high earth-rockfill dam reinforced with geogrids is set up. The comparison between the calculated results and those obtained from shaking table tests shows that they are close and definitely verified each other. Based on this model, the seismic performance of dam with geogrid reinforced are analyzed in practical engineering. And then an effective seismic optimization design will be put forward. Based on the safety, reasonable and economy, the reinforcement design methods of high earth-rockfill with geogrid reinforced under earthquake is recommended. A scientific basis for theoretical research for geogrid reinforced of high earth-rockfill in aseismic measures under earthquake will be provided.There are important theoretical significance and wide application prospect in research findings.

高土石坝抗震研究的重点和目标，主要是根据结构的破坏特征以及工程的破坏机理来提出合理的抗震设计方法和抗震措施，同时研究相应抗震措施的作用机理，从而达到解除地震灾害之虞。本项目通过采用大型三轴试验、直剪试验和非线性有限差分数值模拟，研究土工格栅加筋堆石料作用机理和加固效果，建立土工格栅加筋堆石料静、动力计算模型和拉伸变形模型。基于广义塑性理论和试验基础上，建立复合式动力计算方法和分离式动力计算方法，建立适用于土工格栅加筋高土石坝的弹塑性动力分析程序。在振动台模型试验结果与计算分析相互印证的基础上，将计算程序应用于实际工程，研究土工格栅抗震加固方案对大坝抗震性能的影响，并进行方案优化，在安全、合理、经济的基础上，建议高土石坝的土工格栅加固设计方法。该项研究将为高土石坝土工格栅抗震加固措施的理论研究提供科学依据，研究成果具有重要理论意义和工程应用前景。

高土石坝的一旦因地震失稳破坏会造灾难性的后果。近年来，土工格栅加固土石坝也得到了广泛的应用，已经应用于已建和在建的大坝中。但是这些坝体加固方案的设计多采用工程类比进行的，土工格栅加固高土石坝的机理尚不清楚，缺少定量的分析指导，不便于工程应用。.本课题通过有限差分软件Flac3D，研究了地震作用下土工格栅加筋高土石坝的加固效果，开发了有限差分计算坝坡动力时程安全系数的计算方法，研究了土工格栅的最佳铺设方式，并通过实例进行验证。主要内容如下：.（1）通过强震作用下土工格栅加筋高土石坝的变形分析，计算结果表明，土工格栅加固高土石坝后，降低了坝顶位移，减小了坝体侧移和竖向位移，具有加固高土石坝的效果。通过改变土工格栅弹性模量，土工格栅的长度，土工格栅铺设的层间距等条件，从坝体变形角度选择最佳的铺设方式。.（2）通过拟静力法施加地震荷载结合强度折减法计算得到最大剪应变增量图，计算结果表明，土工格栅加固后滑裂面下移，滑弧加深，土工格栅加固土石坝增加了坝体整体稳定性。通过安全系数时程图，发现加固后安全系数整体增加，坝体的稳定性成增加趋势，对坝体起到加固作用。通过两种强度分析法分析土工格栅的最佳铺设方式。.（3）通过双江口心墙坝的实例验证，按照最佳铺设方式对双江口土石坝进行加固，计算结果表明，坝体的永久变形减小，安全系数增加明显，极限抗震能力也有明显的提高。