弥勒非低矮路基超固结膨胀土地基沉降特征
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摘要
为研究非低矮路基下超固结原状膨胀土地基沉降特征,针对弥勒超固结膨胀土地区路基下地基的物理力学特性与沉降变形特征,开展了一系列原状膨胀土分级连续加载K0固结试验以及现场路基填筑试验,并长期监测路基下地表沉降与路基下地基分层沉降。对比分析天然地基与CFG桩加固地基的沉降特征,地基中的超固结土与正常固结土的分界面深度随路基荷载增大的变化规律及其对地基沉降量的影响。分别采用正常固结法和超固结法计算地基沉降量,并与实测结果进行对比分析,对沉降计算方法进行了深入讨论。研究结果表明:CFG桩加固处理深度应超过超固结土层分布深度,否则与天然地基相比,控制沉降的效果并不明显;超固结沉降计算方法的计算精度明显高于目前设计常用的正常固结沉降计算方法(超固结计算方法的修正系数为0.531,正常固结计算方法的修正系数为0.351),超固结算法-正常固结算法修正系数比随土层深度递减的趋势可用于反映超固结土层的加固处理情况;在路基工程设计中,对于路基荷载下的超固结膨胀土地基,建议采用超固结法沉降计算方法进行沉降分析;在地基加固处理时也应充分利用原状膨胀土的超固结特性,从而在该类地基加固设计中有效降低工程成本。
The objective of this research is to study the settlement characteristics of intact overconsolidated expansive clays with under a non-low embankment.Based on the deformation characteristics of the Mile overconsolidated physical and mechanical properties of the foundation soil subgrade under expansion and settlement,a series of undisturbed expansive soil classification K0 continuous loading consolidation tests and subgrade filling tests were performed,and the longterm settlement of the subgrade surface and settlement of a subgrade under the subgrade were monitored.The settlement characteristics of the natural foundation and CFG(The abbreviation of Cement Fly-ash Gravel,the same below)piles-reinforced foundation were compared and analyzed.The change law of the depth of the interface between the overconsolidated soil and normal consolidated soil with the increase in the subgrade load and its influence on the settlementof the foundation were analyzed.The settlement of the foundation was calculated by the normal consolidation method and over-consolidation method,and the results were compared with the measured results.The settlement calculation method is discussed in depth.The results show that the reinforcement depth of the CFG pile should exceed the depth of the overconsolidation soil layer,otherwise,the effect of the settlement control is not obvious compared with the natural foundation. The precision of the method of overconsolidation settlement calculation is significantly higher than the method of normal consolidation settlement calculation,which is commonly used in current designs.(The modified coefficient of the overconsolidation method is 0.531 and of the normal consolidation method is 0.351)The decrease in the modified coefficient ratios of the overconsolidation and normal consolidation calculation methods with the soil depth can be used to reflect the reinforcement of the foundation in the overconsolidated soil layer.In the design of subgrade engineering,for an overconsolidated expansive soil foundation under a subgrade load,adoption of the overconsolidation method as the settlement calculation method is suggested to analyze the settlement.For the foundation reinforcement treatment,the excess consolidation property of the undisturbed expansive soil should be fully utilized,so that the engineering cost can be effectively reduced in the design of the foundation reinforcement.
The objective of this research is to study the settlement characteristics of intact overconsolidated expansive clays with under a non-low embankment.Based on the deformation characteristics of the Mile overconsolidated physical and mechanical properties of the foundation soil subgrade under expansion and settlement,a series of undisturbed expansive soil classification K0 continuous loading consolidation tests and subgrade filling tests were performed,and the longterm settlement of the subgrade surface and settlement of a subgrade under the subgrade were monitored.The settlement characteristics of the natural foundation and CFG(The abbreviation of Cement Fly-ash Gravel,the same below)piles-reinforced foundation were compared and analyzed.The change law of the depth of the interface between the overconsolidated soil and normal consolidated soil with the increase in the subgrade load and its influence on the settlementof the foundation were analyzed.The settlement of the foundation was calculated by the normal consolidation method and over-consolidation method,and the results were compared with the measured results.The settlement calculation method is discussed in depth.The results show that the reinforcement depth of the CFG pile should exceed the depth of the overconsolidation soil layer,otherwise,the effect of the settlement control is not obvious compared with the natural foundation. The precision of the method of overconsolidation settlement calculation is significantly higher than the method of normal consolidation settlement calculation,which is commonly used in current designs.(The modified coefficient of the overconsolidation method is 0.531 and of the normal consolidation method is 0.351)The decrease in the modified coefficient ratios of the overconsolidation and normal consolidation calculation methods with the soil depth can be used to reflect the reinforcement of the foundation in the overconsolidated soil layer.In the design of subgrade engineering,for an overconsolidated expansive soil foundation under a subgrade load,adoption of the overconsolidation method as the settlement calculation method is suggested to analyze the settlement.For the foundation reinforcement treatment,the excess consolidation property of the undisturbed expansive soil should be fully utilized,so that the engineering cost can be effectively reduced in the design of the foundation reinforcement.
引文
[1]FREDLUND D G,RAHARDJO H.Unsaturated Soils Mechanics in Engineering Practice[M].New York:John Wiley&Sons,2012.
[2]KITAJIMA H,SAFFER D M.Consolidation State of Incoming Sediments to the Nankai Trough Subduction Zone:Implications for Sediment Deformation and Properties[J].Geochemistry,Geophysics,Geosystems,2014,15(7):2821-2839.
[3]TERZAGHI K,PECK R B.Soil Mechanics in Engineering Practice[M].New York:John Wiley&Sons,1967.
[4]FUJIWARA H,YAMANOUCHI T,YAUSUHARA K,et al.Consolidation of Alluvial Clay Under Repeated Loading[J].Soils and Foundations,1985,25(3):19-30.
[5]FUJIWARA H,UE S.Effect of Preloading on Post-construction Consolidation Settlement of Soft Clay Subjected to Repeated Loading[J].Soils and Foundations,1990,30(1):76-86.
[6]KESKIN S N,TEKINSOY M A,UZUNDURUKAN S.The Effects of Over-consolidation Ratio and Effective Stresses to the Earth Pressure at Rest at Clay Soils[J].Teknik Dergi/Technical Journal of Turkish Chamber of Civil Engineers,2004,15(3):3295-3310.
[7]GOURVENEC S M,VULPE C,MURTHY T G.A Method for Predicting the Consolidated Undrained Bearing Capacity of Shallow Foundations[J].Geotechnique,2014,64(3):215-225.
[8]甄文战,孙德安,段博.不同应力路径下超固结黏土试样变形局部化分析[J].岩土力学,2011,32(1):293-298.ZHEN Wen-zhan,SUN De-an,DUAN Bo.Analysis of Strain Localization in Over-consolidated Clay Specimens Along Different Stress Paths[J].Rock and Soil Mechanics,2011,32(1):293-298.
[9]姚仰平,牛雷,韩黎明,等.超固结非饱和土的试验研究[J].岩土力学,2011,32(6):1601-1606.YAO Yang-ping,NIU Lei,HAN Li-ming,et al.Experimental Study of Behaviors of Overconsolidated Unsaturated Clays[J].Rock and Soil Mechanics,2011,32(6):1601-1606.
[10]FARULLA C A,FERRARI A,ROMERO E.Mechanical Behaviour of Compacted Scaly Clay During Cyclic Controlled-suction Testing[C]//SCHANZ T.Experimental Unsaturated Soil Mechanics(Springer Proceeding in Physics).New York:Springer Publishing Company,2007:345-354.
[11]孙磊,王军,孙宏磊,等.循环围压对超固结黏土变形特性影响试验研究[J].岩石力学与工程学报,2015,34(3):594-600.SUN Lei,WANG Jun,SUN Hong-lei,et al.Influence of Cyclic Confining Pressure on Cumulative Deformation Behavior of Overconsolidated Clay[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(3):594-600.
[12]CHEN Wei-zhi,JIANG Guan-lu,ZHAO Hui-shuang,et al.Analysis of Nonlinear Settlement for an Unsaturated Soil Under Stage Continuous Loading[J].Journal Central South University,2014,21(12):4690-4697.
[13]余雷.膨胀土超固结特性及其对地基沉降计算的影响分析[J].铁道建筑,2014,54(8):58-61.YU Lei.Analysis on Super-consolidation Characteristics of Expansive Soil and Its Influence on Foundation Subsidence Calculation[J].Railway Engineering,2014,54(8):58-61.
[14]陈伟志,蒋关鲁,王智猛,等.分级连续加载条件下原状膨胀土固结变形研究[J].岩土力学,2014,35(3):710-716.CHEN Wei-zhi,JIANG Guan-lu,WANG Zhimeng,et al.Study of Consolidation Deformation of Undisturbed Expansive Soil Under Stage Continuous Loading Conditions[J].Rock and Soil Mechanics,2014,35(3):710-716.
[15]陈伟志,蒋关鲁,王智猛,等.弥勒原状膨胀土物理力学参数与固结特性[J].中南大学学报:自然科学版,2014,45(6):1908-1915.CHEN Wei-zhi,JIANG Guan-lu,WANG Zhimeng,et al.Physical-mechanical Parameters and Consolidation Characteristics of Undisturbed Expansive Soil in Mile[J].Journal of Central South University:Science and Technology,2014,45(6):1908-1915.
[16]蒋关鲁,王力伟,杭红星.路桥交界处地基附加应力修正计算方法[J].岩土工程学报,2013,35(2):208-218.JIANG Guan-lu,WANG Li-wei,HANG Hongxing.Modified Additional Stress Calculation Method of Bridge Approach Foundation Under Subgrade Load[J].Chinese Journal of Geotechnical Engineering,2013,35(2):208-218.
[17]蒋关鲁,王海龙,李安洪,等.土质路基荷载下地基反力试验研究[J].铁道学报,2012,34(6):69-74.JIANG Guan-lu,WANG Hai-long,LI An-hong,et al.Experimental Study on Ground Reaction Under Loading of Soil Subgrade[J].Journal of the China Railway Society,2012,34(6):69-74.
[18]JGJ 79—2012,建筑地基处理技术规范[S].JGJ 79—2012,Technical Code for Ground Treatment of Buildings[S].
[19]陈伟志,蒋关鲁,赵慧爽,等.铁路路基下膨胀土地基浸水响应现场试验[J].岩土工程学报,2014,36(8):1507-1514.CHEN Wei-zhi,JIANG Guan-lu,ZHAO Huishuang,et al.Field Tests on Soaking Response of Expansive Soil Foundation Under Railway Subgrade[J].Chinese Journal of Geotechnical Engineering,2014,36(8):1507-1514.
[2]KITAJIMA H,SAFFER D M.Consolidation State of Incoming Sediments to the Nankai Trough Subduction Zone:Implications for Sediment Deformation and Properties[J].Geochemistry,Geophysics,Geosystems,2014,15(7):2821-2839.
[3]TERZAGHI K,PECK R B.Soil Mechanics in Engineering Practice[M].New York:John Wiley&Sons,1967.
[4]FUJIWARA H,YAMANOUCHI T,YAUSUHARA K,et al.Consolidation of Alluvial Clay Under Repeated Loading[J].Soils and Foundations,1985,25(3):19-30.
[5]FUJIWARA H,UE S.Effect of Preloading on Post-construction Consolidation Settlement of Soft Clay Subjected to Repeated Loading[J].Soils and Foundations,1990,30(1):76-86.
[6]KESKIN S N,TEKINSOY M A,UZUNDURUKAN S.The Effects of Over-consolidation Ratio and Effective Stresses to the Earth Pressure at Rest at Clay Soils[J].Teknik Dergi/Technical Journal of Turkish Chamber of Civil Engineers,2004,15(3):3295-3310.
[7]GOURVENEC S M,VULPE C,MURTHY T G.A Method for Predicting the Consolidated Undrained Bearing Capacity of Shallow Foundations[J].Geotechnique,2014,64(3):215-225.
[8]甄文战,孙德安,段博.不同应力路径下超固结黏土试样变形局部化分析[J].岩土力学,2011,32(1):293-298.ZHEN Wen-zhan,SUN De-an,DUAN Bo.Analysis of Strain Localization in Over-consolidated Clay Specimens Along Different Stress Paths[J].Rock and Soil Mechanics,2011,32(1):293-298.
[9]姚仰平,牛雷,韩黎明,等.超固结非饱和土的试验研究[J].岩土力学,2011,32(6):1601-1606.YAO Yang-ping,NIU Lei,HAN Li-ming,et al.Experimental Study of Behaviors of Overconsolidated Unsaturated Clays[J].Rock and Soil Mechanics,2011,32(6):1601-1606.
[10]FARULLA C A,FERRARI A,ROMERO E.Mechanical Behaviour of Compacted Scaly Clay During Cyclic Controlled-suction Testing[C]//SCHANZ T.Experimental Unsaturated Soil Mechanics(Springer Proceeding in Physics).New York:Springer Publishing Company,2007:345-354.
[11]孙磊,王军,孙宏磊,等.循环围压对超固结黏土变形特性影响试验研究[J].岩石力学与工程学报,2015,34(3):594-600.SUN Lei,WANG Jun,SUN Hong-lei,et al.Influence of Cyclic Confining Pressure on Cumulative Deformation Behavior of Overconsolidated Clay[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(3):594-600.
[12]CHEN Wei-zhi,JIANG Guan-lu,ZHAO Hui-shuang,et al.Analysis of Nonlinear Settlement for an Unsaturated Soil Under Stage Continuous Loading[J].Journal Central South University,2014,21(12):4690-4697.
[13]余雷.膨胀土超固结特性及其对地基沉降计算的影响分析[J].铁道建筑,2014,54(8):58-61.YU Lei.Analysis on Super-consolidation Characteristics of Expansive Soil and Its Influence on Foundation Subsidence Calculation[J].Railway Engineering,2014,54(8):58-61.
[14]陈伟志,蒋关鲁,王智猛,等.分级连续加载条件下原状膨胀土固结变形研究[J].岩土力学,2014,35(3):710-716.CHEN Wei-zhi,JIANG Guan-lu,WANG Zhimeng,et al.Study of Consolidation Deformation of Undisturbed Expansive Soil Under Stage Continuous Loading Conditions[J].Rock and Soil Mechanics,2014,35(3):710-716.
[15]陈伟志,蒋关鲁,王智猛,等.弥勒原状膨胀土物理力学参数与固结特性[J].中南大学学报:自然科学版,2014,45(6):1908-1915.CHEN Wei-zhi,JIANG Guan-lu,WANG Zhimeng,et al.Physical-mechanical Parameters and Consolidation Characteristics of Undisturbed Expansive Soil in Mile[J].Journal of Central South University:Science and Technology,2014,45(6):1908-1915.
[16]蒋关鲁,王力伟,杭红星.路桥交界处地基附加应力修正计算方法[J].岩土工程学报,2013,35(2):208-218.JIANG Guan-lu,WANG Li-wei,HANG Hongxing.Modified Additional Stress Calculation Method of Bridge Approach Foundation Under Subgrade Load[J].Chinese Journal of Geotechnical Engineering,2013,35(2):208-218.
[17]蒋关鲁,王海龙,李安洪,等.土质路基荷载下地基反力试验研究[J].铁道学报,2012,34(6):69-74.JIANG Guan-lu,WANG Hai-long,LI An-hong,et al.Experimental Study on Ground Reaction Under Loading of Soil Subgrade[J].Journal of the China Railway Society,2012,34(6):69-74.
[18]JGJ 79—2012,建筑地基处理技术规范[S].JGJ 79—2012,Technical Code for Ground Treatment of Buildings[S].
[19]陈伟志,蒋关鲁,赵慧爽,等.铁路路基下膨胀土地基浸水响应现场试验[J].岩土工程学报,2014,36(8):1507-1514.CHEN Wei-zhi,JIANG Guan-lu,ZHAO Huishuang,et al.Field Tests on Soaking Response of Expansive Soil Foundation Under Railway Subgrade[J].Chinese Journal of Geotechnical Engineering,2014,36(8):1507-1514.