东南沿海地区玄武岩残积土雨水运移特征及滑坡失稳数值模拟
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摘要
暴雨作用下,东南沿海地区玄武岩残积土滑坡极易失稳,但相关的研究较为少见。文章以浙江省温州市马济头滑坡为对象,首先利用原状土土柱实验,获取中峰型和前峰型降雨工况下玄武岩残积土的雨水运移特征;然后使用Geostudio软件反演土柱降雨实验,获取玄武岩残积土的非饱和渗透参数;接着通过数值模拟,获取两种降雨工况下马济头滑坡的渗流场及稳定性。结果表明:降雨作用下,玄武岩残积土的浅层土体含水率增长速率较快,上部及深部土体更易达到饱和; 10 mm/h降雨强度下,湿润锋下渗速率较小且不随深度变化; 30 mm/h降雨强度下,湿润锋下渗速率可增大2～3倍,雨水主要在峰值降雨期快速入渗;降雨作用下,马济头滑坡的滑带土饱和度迅速增大,孔隙水压力随之增大,坡脚出现大面积滞水,土体抗剪强度急剧降低,模拟降雨第三天,滑坡的稳定性系数降至最低,滑坡最终失稳;中峰型降雨工况下雨水入渗速率更快,坡脚处产生更大滞水面积,滑坡更容易失稳。本文的研究成果可为东南沿海玄武岩残积土滑坡的稳定性评价提供理论依据。
Slopes in the basalt residual soil in the coastal areas of southeast China are easy to fall during the typhoon rainstorm. However,this aspect was seldom examined. In this paper,the Majitou landslide is chosen as a sample,and the undisturbed soil column tests are conducted to get the rainwater migration and distribution characteristics of the basalt residual soils under the central and advanced rainfall conditions. Geostudio software is used to retrieve the soil column tests to obtain the unsaturated seepage parameters of the soil.The above results are applied to the numerical simulation to obtain the seepage field and slope stability of the Majitou landslide under the two rainfall conditions. The results indicate that the volumetric water contents in the upper and bottom parts of the soil column increase greatly during rainfall; under the rainfall intensity of 10 mm/h,the migration velocity of wetting front is low and unchanged with depths; while under the rainfall intensity of 30 mm/h,the migration velocity is 2-3 times greater than the former and decreases gradually with depth. Rainwater rapidly enters the basalt residual soil during the peak rainfall,and after three days' rainfall,the soil saturation and the pore-water pressure of the Majitou landslide increase rapidly. The perched water appears at the foot of the slope,the soil shear strength decreases sharply,and the slope is unstable. The rainwater movement velocities under the central rainfall conditions are faster,which lead to the larger perched water area,and the landslide is easier to induce. The results in this paper may provide theoretical background for the stability evaluation and treatment for slopes in the basaltic residual soil in the coastal regions in southeast China.
Slopes in the basalt residual soil in the coastal areas of southeast China are easy to fall during the typhoon rainstorm. However,this aspect was seldom examined. In this paper,the Majitou landslide is chosen as a sample,and the undisturbed soil column tests are conducted to get the rainwater migration and distribution characteristics of the basalt residual soils under the central and advanced rainfall conditions. Geostudio software is used to retrieve the soil column tests to obtain the unsaturated seepage parameters of the soil.The above results are applied to the numerical simulation to obtain the seepage field and slope stability of the Majitou landslide under the two rainfall conditions. The results indicate that the volumetric water contents in the upper and bottom parts of the soil column increase greatly during rainfall; under the rainfall intensity of 10 mm/h,the migration velocity of wetting front is low and unchanged with depths; while under the rainfall intensity of 30 mm/h,the migration velocity is 2-3 times greater than the former and decreases gradually with depth. Rainwater rapidly enters the basalt residual soil during the peak rainfall,and after three days' rainfall,the soil saturation and the pore-water pressure of the Majitou landslide increase rapidly. The perched water appears at the foot of the slope,the soil shear strength decreases sharply,and the slope is unstable. The rainwater movement velocities under the central rainfall conditions are faster,which lead to the larger perched water area,and the landslide is easier to induce. The results in this paper may provide theoretical background for the stability evaluation and treatment for slopes in the basaltic residual soil in the coastal regions in southeast China.
引文
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[2] GASMO JM, RAHARDJO H, LEONG E C.Infiltration effects on stability of a residual soil slope[J]. Computers and geotechnics,2000,26(2):145-165.
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[4]余沛,张著芳,魏厚振,等.考虑干湿循环影响下玄武岩残积土渗透系数的试验研究[J].水利与建筑工程学报,2011,9(5):63-66.[YU P,ZHANG Z F, WEI H Z, et al. Experimental study on permeability coefficient of basalt residual soil considering influence of drying and wetting cycle[J].Journal of Water Resources&Architectural Engineering,2011,9(5):63-66.(in Chinese)]
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[6]王一鸣,殷坤龙.台风暴雨型泥石流单沟危险度研究[J].水文地质工程地质,2018,45(3):124-130.[WANG Y M,YIN K L. A study of the typhoontriggered debris flow hazard degree of a single gully[J]. Hydrogeology&Engineering Geology,2018,45(3):124-130.(in Chinese)]
[7]张泰丽,周爱国,施斌,等.台风暴雨条件下滑坡变形特征物理试验研究[J].水文地质工程地质,2016,43(6):127-132.[ZHANG T L,ZHOU A G,SHI B,et al. Physical experiment research on landslide deformation characteristics under the condition of the typhoon heavy rain[J]. Hydrogeology&Engineering Geology,2016,43(6):127-132.(in Chinese)]
[8] CUOMO S,SALA M D. Rainfall-induced infiltration,runoff and failure in steep unsaturated shallow soil deposits[J]. Engineering Geology,2013,162(14):118-127.
[9]朱伟,陈学东,钟小春.降雨入渗规律的实测与分析[J].岩土力学,2006,27(11):1873-18.[ZHU W,CHEN X D, ZHONG X C. Observation and analysis of rainfall infiltration[J]. Rock&Soil Mechanics,2006, 27(11):1873-1879.(in Chinese)]
[10] GOFAR N,LEE M L, KASSIM A. Response of suction distribution to rainfall infiltration in soil slope[J]. Electronic Journal of Geotechnical Engineering,EJGE,2008,13(E):1-13.
[11] RAO M D, RAGHUWANSHI N S, SINGH R.Development of a physically based 1D-infiltration model for irrigated soils[J]. Agricultural water management,2006,85(1/2):165-174.
[12] HENCHER S R. Preferential flow paths through soil and rock and their association with landslides[J].Hydrological Processes,2010,24(12):1610-1630.
[13]张晨阳,张明,张泰丽,等.侵入岩脉风化壳对中林村残积土滑坡渗流场和稳定性的影响[J].岩土力学,2018,39(7):313-321.[ZHANG C Y,ZHANG M,ZHANG T L,et al. Impact of Dyke and its residual soil on seepage and stability of Zhonglin landslide[J]. Rock&Soil Mechanics,2018,39(7):313-321.(in Chinese)]
[14] RAHARDJO H,LEONG E C,REZAUR R B. Effect of antecedent rainfall on pore-water pressure distribution characteristics in residual soil slopes under tropical rainfall[J]. Hydrological Processes,2008,22(4):506-523.
[15] VAN GENUCHTEN M T. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J]. Soil science society of America journal,1980,44(5):892-898.
[16] KIM D H,KIM S K,GRATCHEV I. Unsaturated seepage behavior study using soil column test[C]//Singapore:Southeast Asian Geotechnical Conference,2013.
[17] FREDLUND D G,MORGENSTERN N R,WIDGER R A. The shear strength of unsaturated soils[J].Canadian geotechnical journal,1978,15(3):313-321.
[2] GASMO JM, RAHARDJO H, LEONG E C.Infiltration effects on stability of a residual soil slope[J]. Computers and geotechnics,2000,26(2):145-165.
[3] MUKHLISIN M,TAHA M R. Numerical model of antecedent rainfall effect on slope stability at a hillslope of weathered granitic soil formation[J].Journal of the Geological Society of India,2012,79(5):525-531.
[4]余沛,张著芳,魏厚振,等.考虑干湿循环影响下玄武岩残积土渗透系数的试验研究[J].水利与建筑工程学报,2011,9(5):63-66.[YU P,ZHANG Z F, WEI H Z, et al. Experimental study on permeability coefficient of basalt residual soil considering influence of drying and wetting cycle[J].Journal of Water Resources&Architectural Engineering,2011,9(5):63-66.(in Chinese)]
[5]周容方.贵州玄武岩残积土边坡稳定性分析[D].武汉:武汉科技大学,2013.[ZHOU R F. The slope stability analysis of basalt residual soil in Guizhou[D]. Wuhan:Wuhan University of Science and Technology,2013.(in Chinese)]
[6]王一鸣,殷坤龙.台风暴雨型泥石流单沟危险度研究[J].水文地质工程地质,2018,45(3):124-130.[WANG Y M,YIN K L. A study of the typhoontriggered debris flow hazard degree of a single gully[J]. Hydrogeology&Engineering Geology,2018,45(3):124-130.(in Chinese)]
[7]张泰丽,周爱国,施斌,等.台风暴雨条件下滑坡变形特征物理试验研究[J].水文地质工程地质,2016,43(6):127-132.[ZHANG T L,ZHOU A G,SHI B,et al. Physical experiment research on landslide deformation characteristics under the condition of the typhoon heavy rain[J]. Hydrogeology&Engineering Geology,2016,43(6):127-132.(in Chinese)]
[8] CUOMO S,SALA M D. Rainfall-induced infiltration,runoff and failure in steep unsaturated shallow soil deposits[J]. Engineering Geology,2013,162(14):118-127.
[9]朱伟,陈学东,钟小春.降雨入渗规律的实测与分析[J].岩土力学,2006,27(11):1873-18.[ZHU W,CHEN X D, ZHONG X C. Observation and analysis of rainfall infiltration[J]. Rock&Soil Mechanics,2006, 27(11):1873-1879.(in Chinese)]
[10] GOFAR N,LEE M L, KASSIM A. Response of suction distribution to rainfall infiltration in soil slope[J]. Electronic Journal of Geotechnical Engineering,EJGE,2008,13(E):1-13.
[11] RAO M D, RAGHUWANSHI N S, SINGH R.Development of a physically based 1D-infiltration model for irrigated soils[J]. Agricultural water management,2006,85(1/2):165-174.
[12] HENCHER S R. Preferential flow paths through soil and rock and their association with landslides[J].Hydrological Processes,2010,24(12):1610-1630.
[13]张晨阳,张明,张泰丽,等.侵入岩脉风化壳对中林村残积土滑坡渗流场和稳定性的影响[J].岩土力学,2018,39(7):313-321.[ZHANG C Y,ZHANG M,ZHANG T L,et al. Impact of Dyke and its residual soil on seepage and stability of Zhonglin landslide[J]. Rock&Soil Mechanics,2018,39(7):313-321.(in Chinese)]
[14] RAHARDJO H,LEONG E C,REZAUR R B. Effect of antecedent rainfall on pore-water pressure distribution characteristics in residual soil slopes under tropical rainfall[J]. Hydrological Processes,2008,22(4):506-523.
[15] VAN GENUCHTEN M T. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J]. Soil science society of America journal,1980,44(5):892-898.
[16] KIM D H,KIM S K,GRATCHEV I. Unsaturated seepage behavior study using soil column test[C]//Singapore:Southeast Asian Geotechnical Conference,2013.
[17] FREDLUND D G,MORGENSTERN N R,WIDGER R A. The shear strength of unsaturated soils[J].Canadian geotechnical journal,1978,15(3):313-321.
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