川南某换流站复杂堆积体边坡开挖变形机制及抗震加固效果评价

The excavation deformation mechanism and the seismic reinforcement effect evaluation of complex accumulation slope of a converter station in Southern Sichuan

西南山区广泛分布的复杂堆积体边坡开挖变形机制对换流站建设具有重大制约作用。为解决白鹤滩—江苏某特高压输电工程换流站建设的紧迫需求,以拟建站址区堆积体边坡为研究对象,采用深部位移监测、原位试验和FLAC3D数值模拟相结合的手段,对该堆积体边坡开挖变形机制及不同设计方案、不同桩参数条件下的抗震加固效果进行评价,并分析其抗震加固机理。结果表明:①换流站“多成因类型土体”的复杂堆积体边坡开挖极易产生变形,失稳模式为“牵引式蠕滑-拉裂”;②开挖过程中形成的高陡临空面是导致此类堆积体边坡变形的主控因素,堆积体边坡土体的高水敏性是短历时强降雨后坡体变形加剧的内在诱因;③经过圆形抗滑桩和矩形抗滑桩两种边坡加固方案治理后,坡体变形量均显著降低,坡体内最大变形位置位于坡体中后部,堆积体边坡在天然、地震工况下的稳定系数均符合设计要求,采用矩形抗滑桩对此类型堆积体边坡的治理具有更高的抗滑支挡效益和经济效益;④地震工况下,抗滑桩桩顶变形最大,剪力和弯矩随着地震波的增加呈先增加后减小,最终达到最大值的变化趋势,最大弯矩值位于抗滑桩桩身约1/2处,边坡的支挡设计应结合桩身剪力、弯矩等分布规律进行。研究成果可为类似工程的设计和施工提供参考。

The excavation deformation mechanism of the widely distributed complex accumulation slopes in the southwestern mountainous areas has a significant restriction effect on the construction of converter stations.To address the urgent needs of the converter station construction in Baihetan-Jiangsu UHV transmission project,the authors in this paper took the accumulation slope in the proposed station site as the research object,and adopted the deep displacement monitoring,in-situ test and FLAC3D numerical simulation methods to evaluale the excavation deformation mechanism of this accumulation slope and the seismic reinforcement effect under different design schemes and different pile parameters.Then the seismic reinforcement mechanism is analyzed.The results are as follows.①The excavation of the complex accumulative slope of“multi-genetic type soil”in the converter station is prone to deformation,and the instability mode is“traction creep and tension failure mode”.②The high and steep free face formed in the excavation process is the main factor leading to the accumulation slope deformation,and the high-water sensitivity of the accumulation slope soil is the internal inducement of the slope deformation aggravation after short duration heavy rainfall.③Under the two slope reinforcement schemes of circular anti-slide pile and rectangular anti-slide pile,the deformation amount of the slope body is significantly reduced,and the maximum deformation position in the slope body is located in the middle and back of the slope body.The stability coefficient of the accumulation body slope under natural and seismic conditions meets the design requirements.The use of rectangular anti-slide pile in the treatment of the accumulation body slope has higher anti-slide retaining and economic benefits.④The top deformation of the anti-slide pile is the largest under seismic condition,and the shear force and bending moment increase first and then decrease with the increase of seismic wave,and finally reach the maximum change trend.The maximum bending moment value is about 1/2 of the anti-slide pile body.The retaining design of slope should be combined with the distribution law of pile shear force and bending moment.The research results of this paper could provide some references for the design and construction of similar projects.