四川宜宾井场滑坡成因分析与治理措施
Cause analysis and control measures of landslide in Yibin well site of Sichuan Province
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摘要: 四川宜宾珙县的某油气井场位于古滑覆堆积体上,因井场作业平台开挖导致古滑堆积体局部复活,在2018年3月时发生滑塌,处于蠕动变形中。据现场调查表明,该井场滑坡平面形态呈舌状,纵长约200 m,横向宽度约150 m,滑坡前后缘高差约35 m,钻探结构滑体厚度约8 m,推测滑坡体积约为27×104 m3。井场滑坡在平面上分为4个变形区域,在井场平台和滑体中后部发育大量张拉裂缝和隆起开裂,裂缝宽度约4~8 cm,隆起高度达 21~35 cm。特殊的地形条件和土层结构造成滑坡出现多层滑面。考虑到井场滑坡属于边滑边治的情况,选定治理方案主要为抗滑桩+锚索+桩间网喷+桩顶连系梁+挡墙+截排水沟,并通过后期监测验证方案的合理性。监测结果表明: 各监测点抗滑桩的桩顶水平位移和竖向位移逐渐收敛,趋于稳定,锚索应力呈现平缓状态,稳定在14 kN左右。该治理方案应用性较好,可为相关项目提供设计参考。Abstract: An oil and gas well site in Gongxian County of Yibin in Sichuan Province is located on the ancient sliding accumulation body. Due to the excavation of the well site operation platform, the ancient sliding accumulation body was partially revived, and the ancient sliding accumulation body collapsed in March 2018, which was in the process of creeping deformation. According to the field survey, the landslide at the well site is tongue-shaped in plane, with a length of about 200 m and a width of about 150 m. The height difference between the front and rear edges of the landslide is about 35 m, and the thickness of the drilling structure slide is about 8m. It is estimated that the volume of the landslide is about 27×104 m3. The well site landslide is divided into four deformation areas on the plane, and a large number of tension fractures and uplift cracks were developed on the well site platform and the middle and back of the slide body, with cracks width of 4 to 8 cm and uplift height of 21 to 35 cm. The special terrain condition and soil layer structure cause the multi-layer sliding surface of the landslide. Considering that the landslide at the well site belongs to the situation of side-slip treatment, the selected treatment plan is mainly anti-slide pile + anchor cable + net spraying between piles + pile top connecting beam + retaining wall + cut-off drainage ditch, and the plan has passed the post-monitoring verification. The results show that the horizontal and vertical displacements of the anti-sliding piles at each monitoring point gradually converge and tend to be stable, and the stress of the anchor cable is in a gentle state with stable of 14 kN. This control scheme has good applicability, and provide design reference for related projects.