蓄洪区路堤边坡浸润线及安全系数变化规律
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摘要
基于修建于蓄洪区范围内的公路边坡将受洪水浸泡,引入非饱和渗流理论,利用孔隙压力为0 kPa的条件确定蓄洪过程中的边坡浸润线位置,并在条分法中采用侧面水压力等效计算土坡中的渗流力,对水位完全慢速下降过程中边坡安全系数进行计算;将蓄洪过程分为水位上升期、蓄洪期和水位下降期,令蓄洪水位为10 m,水位上升速率为0.2 m/d,水位下降速率为0.5 m/d,采用本文方法对饱和渗透系数分别为10-6,10-7和10-8 m/s的边坡安全系数变化规律进行计算分析。研究结果表明:蓄洪期内边坡浸润线均达不到稳定状态,且渗透系数越小,边坡内浸润线的变化越小;蓄洪水位上升期边坡安全系数增大,且渗透性较高的土坡安全系数上升速率比渗透系数低的土体安全系数上升速率慢;蓄洪期内,当蓄洪时长比s即蓄洪时长t与总时长T之比相等时,高渗透性边坡安全系数下降率较大;水位下降期内边坡安全系数随下降比增大而变小,蓄洪时间越长安全系数越小,但安全系数下降率基本不受蓄洪时间的影响,其规律可采用抛物线近似模拟。
Based on the fact that road embankment located in flood storage district will emerge in flood period,the unsaturated soil seepage theory was introduced to analyze pore water pressure distribution in embankment,and the phreatic line was determined when pore water pressure is 0 kPa.Water pressure on side of soil slice was applied to determine the seepage force equivalently.The embankment in slowly drawdown condition was analyzed by this method.Then,the whole flood storage period was considered composing of water level rising time,water level keeping time and water level lowering time,when the maximun water level was 10 m,water level rising rate was 0.2 m/d,water level lowering rate was 0.5 m/d,and then the variation of factor of safety of embankment,whose permeability coefficient was 10-6,10-7,and 10-8 m/s respectively,were studied.The results show that the phreatic line will not reach final level in flood storage period,and the smaller the permeability,the less change of the line.In water level rising time,factor of safety will be enlarged,and the rate is smaller when the soil of the embankment has larger permeability.In flood storage time,in the same s(s=t/T),the factor of safety of embankment decreases at higher rate when it is of larger permeability;in water level lowering time,the longer the storage time,the smaller the factor of safety,while lowering rate of factor of safety is not influenced by flood storage time.
Based on the fact that road embankment located in flood storage district will emerge in flood period,the unsaturated soil seepage theory was introduced to analyze pore water pressure distribution in embankment,and the phreatic line was determined when pore water pressure is 0 kPa.Water pressure on side of soil slice was applied to determine the seepage force equivalently.The embankment in slowly drawdown condition was analyzed by this method.Then,the whole flood storage period was considered composing of water level rising time,water level keeping time and water level lowering time,when the maximun water level was 10 m,water level rising rate was 0.2 m/d,water level lowering rate was 0.5 m/d,and then the variation of factor of safety of embankment,whose permeability coefficient was 10-6,10-7,and 10-8 m/s respectively,were studied.The results show that the phreatic line will not reach final level in flood storage period,and the smaller the permeability,the less change of the line.In water level rising time,factor of safety will be enlarged,and the rate is smaller when the soil of the embankment has larger permeability.In flood storage time,in the same s(s=t/T),the factor of safety of embankment decreases at higher rate when it is of larger permeability;in water level lowering time,the longer the storage time,the smaller the factor of safety,while lowering rate of factor of safety is not influenced by flood storage time.
引文
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[14]Fredlund D G,XING An-qing.Equations for the soil-characteristic curve[J].Can Geotech,1994,31:524-526.
[2]Lane P A,Griffiths D V.Assessment of stability of slopes underdrawdown conditions[J].Journal of Geotechnical andGeoenvironmental Engineering,2000,126:443-450.
[3]Mehmet M.Berilgen.Investigation of stability of slopes underdrawdown conditions[J].Computers and Geotechnics,2007,34:81-91.
[4]Viratjandr C,Michalowski R L.Limit analysis of submergedslopes subjected to water drawdown[J].Can Geotech J,2006,43(8):802-814.
[5]徐光明,王国利,顾行文,等.雨水入渗与膨胀性土边坡稳定性试验研究[J].岩土工程报,2006,28(2):270-273.XU Guang-ming,WANG Guo-li,GU Xing-wen,et al.Centrifuge modeling for instability of excavated slope inexpansive soil due to water infiltration[J].Chinese Journal ofGeotechnical Engineering,2006,28(2):270-273.
[6]郑颖人,时卫民,孔位学.库水位下降时渗透力及地下水浸润线的计算[J].岩石力学与工程学报,2004,23(18):3203-3204.ZHENG Yin-ren,SHI Wei-ming,KONG Wei-xue.Calculation ofseepage forces and phreatic surface under drawdownconditions[J].Chinese Journal of Rock Mechanics andEngineering,2004,23(18):3203-3204.
[7]万少石.涉水边坡稳定性的三维强度折减有限元分析[D].大连:大连理工大学土木水利学院,2009:55-62.WAN Shao-shi.Three-dimensional slope stability analysis byshear strength reduction finite element method(SSR-FEM)under drawdown condition[D].Dalian:Dalian University ofTechnology.School of Civil and Hydraulic Engineering,2009:55-62.
[8]王飞跃,杨铠腾,徐志胜,等.基于浸润线矩阵的尾矿坝稳定性分析[J].岩土力学,2009,30(3):840-844.WANG Fei-yue,YANG Kai-teng,XU Zhi-sheng,et al.Stabilityanalysis of tailings dam based on saturation line matrix[J].Rockand Soil Mechanics,2009,30(3):840-844.
[9]高玉峰,范昭平.多点、多向地震作用下非圆弧滑面边坡稳定分析通用条分法[J].岩土力学,2010,31(12):3816-3817.GAO Yu-feng,FAN Zhao-ping.Generalized slice method forstability analysis of slope with non-circular slide face undermultipoint and multidirection seismic ground motions[J].Rockand Soil Mechanics,2010,31(12):3816-3817.
[10]毛昶熙,李吉庆,段祥宝.渗流作用下土坡圆弧滑动有限元计算[J].岩土工程学报,2001,23(6):659-665.MAO Chang-xi,LI Ji-qing,DUAN Xiang-bao.Finite elementcalculation on circular slip of earth slope under seepage action[J].Chinese Journal of Geotechnical Engineering,2001,23(6):659-665.
[11]时卫民,付玉峰.条分法中土条周边水压力与渗透力之间的关系[J].岩土工程技术,2007,21(3):123-125.SHI Wei-min,FU Yu-hui.Relations between seepage force andwater pressure around slice in slice method[J].GeotechnicalEngineering Technique,2007,21(3):123-125.
[12]毛昶熙,段祥宝,吴良骥.再论渗透力及其应用[J].长江科学院院报,2009,26(增刊1):1-5.MAO Chang-xi,DUAN Xiang-bao,WU Liang-ji.Discussionagain on seepage force and its application[J].Journal of YangtzeRiver Scientific Research Institute,2009,26(S1):1-5.
[13]王旭升,常宏,谭建民.斜坡地下水渗透力计算与稳定性分析[J].水文地质工程地质,2003(2):41-45.WANG Xu-sheng,CHANG Hong,TAN Jian-min.Calculation ofgroundwater seepage force and stability analysis of slopes[J].Hydrogeology and Engineering Geology,2003(2):41-45.
[14]Fredlund D G,XING An-qing.Equations for the soil-characteristic curve[J].Can Geotech,1994,31:524-526.
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