阳洼水坠坝聚乙烯微孔波纹管排渗试验研究

为探索水坠筑坝中效果好、造价低的排水设施新形式,在阳洼水坠坝施工中采用聚乙烯微孔波纹管排水系统替代了沙井、沙沟和褥垫等排水设施。微孔波纹管用土工布或棕皮包扎后在坝内呈纵向、横向、竖向布设,形成网状排水系统。大坝实际冲填166天,日冲填速度0.2m,平均泥浆含水量45.72％。施工期坝体含水量、干容重、孔隙水压力、渗流量和冲填体抗剪强度等观测分析表明,波纹管排水系统加快了泥浆脱水固结,使流态区深度至少降低1/4,孔隙水压力消散速率提高约30％,冲填结束7个月后,坝体下部含水量降到27％,干容重达1.5～1.6g/cm~3,坝体固结程度达70％～80％,既保证了施工期的坝体稳定,又缩窄了碾压边埂宽度20％～30％,比采用沙井、沙沟排水可降低排水工程投资60％。

Experimental Study on the Drainage System by Polyethylene Corrugated Pipe with Micro-apertures in the Construction of Yangwa Hydraulic Fill Earth Dam

For probing into a new type of drainage system with better effect and lower cost in construction of hydraulic fill earth dam, the drainage systems such as pillar filter body, horizontal filter layers and filter blanket at the bottom of the dam were replaced by the drainage system installed with polyethylene corrugated pipes with micro-apertures in the construction of Yangwa hydraulic fill earth dam. The micro-aperture corrugated pipes packed with geotextile fabrics or palm barks laying out in horizontal and vertical directions form a reticulated drainage system. The dam was filled for 166 days with filling velocity 0. 2m per day and mean water content in the slurry was 45. 7%. Observations on the water content, dry bulk density, pore pressure, seepage quantity and shear-resistance intensity of the filled body etc. indicated that the new drainage system sped up the dehydration and consolidation of slurry, reduced the depth of flow of filling material by 25 % and increased the dispersion rate of pore pressure by 30%. Seven months after the filling, the water content in lower part of the dam decreased to 27%, dry bulk density reached 1. 5-1. 6g/cm3 and the degree of con-solidation of the dam body reached 70% - 80%. The drainage system not only ensured the stability of dam during construction period but also narrowed the width of side banks by 20%-30%. Cost of the new drainage system was reduced by 60% as compared with the conventionally adopted drainage system.