南宁地铁区域饱和圆砾土大型动三轴试验研究
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摘要
以南宁地铁区域圆砾层土质为研究对象,对饱和状态下的圆砾土开展了一系列大型排水动三轴试验,分析了相对密实度、动应力幅值和振动次数对饱和圆砾土累积应变、应力–应变滞回圈和孔压的影响。研究表明,饱和圆砾土累积轴向应变?–振动次数N曲线在动应力幅值较小时为稳定型曲线,呈双曲线增长规律,其参数?与初始相对密实度Dr呈线性关系;动应力幅值较大时为破坏型曲线,呈幂函数增长规律。饱和圆砾土应力应变滞回圈形状呈双直线型,其面积在动应力幅值较小时随着振动次数的增加先增大后减小,其割线模量随着振动次数的增加先减小后增大。饱和圆砾土的孔压在动应力幅值较小时随着振动次数的增加先增大再减小,且循环加载后期Dr=0.5试样的孔压大于Dr=0.3和Dr=0.7试样的孔压,这与不同初始相对密实度条件下粗粒土的破碎特性有关。
The gravel soil in Nanning metro area is taken as the research object, and a series of large-scale drained dynamic triaxial tests are conducted on saturated gravel. The effects of the relative density, dynamic stress amplitude and number of loading cycles on the accumulation strain, stress-strain hysteresis loops and pore pressure of saturated round gravel are analyzed. The experimental results show that when the dynamic stress amplitudes are small, the curves of accumulated axial strain with number of loading cycles are stable with the increasing rule of hyperbolic function. A linear relation between the parameter α in the hyperbolic function and the relative density Dr is found. However, the curves exhibit failure type and the increasing rule conforms to power function under a large dynamic stress amplitude. The stress-strain hysteresis loops of saturated round gravel exhibit double-lined type. When the dynamic stress amplitude is small, with the increasing number of loading cycles, the area of hysteresis loops firstly increases and then decreases, the secant modulus firstly decreases and then increases, and the pore pressure firstly increases and then decreases. In the later period of cyclic loading, the pore pressure is high when Dr=0.5 in comparison to the situation Dr=0.3 or 0.7, and this result relates to the gravel breaking characteristics at different initial relative densities.
The gravel soil in Nanning metro area is taken as the research object, and a series of large-scale drained dynamic triaxial tests are conducted on saturated gravel. The effects of the relative density, dynamic stress amplitude and number of loading cycles on the accumulation strain, stress-strain hysteresis loops and pore pressure of saturated round gravel are analyzed. The experimental results show that when the dynamic stress amplitudes are small, the curves of accumulated axial strain with number of loading cycles are stable with the increasing rule of hyperbolic function. A linear relation between the parameter α in the hyperbolic function and the relative density Dr is found. However, the curves exhibit failure type and the increasing rule conforms to power function under a large dynamic stress amplitude. The stress-strain hysteresis loops of saturated round gravel exhibit double-lined type. When the dynamic stress amplitude is small, with the increasing number of loading cycles, the area of hysteresis loops firstly increases and then decreases, the secant modulus firstly decreases and then increases, and the pore pressure firstly increases and then decreases. In the later period of cyclic loading, the pore pressure is high when Dr=0.5 in comparison to the situation Dr=0.3 or 0.7, and this result relates to the gravel breaking characteristics at different initial relative densities.
引文
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[19]田海,孔令伟,赵翀.基于粒度熵概念的贝壳砂颗粒破碎特性描述[J].岩土工程学报,2014,36(6):1152-1159.(TIAN Hai,KONG Ling-wei,ZHAO Chong,et al.Characterization of partical breakage with grading entropy on shell sand[J].Chinese Journal of Geotechnical Engineering,2014,36(6):1152-1159.(in Chinese))
[2]黄茂松,姚仰平,尹振宇,等.土的基本特性及本构关系与强度理论[J].土木工程学报,2016,49(7):9-35.(HUANGMao-song,YAO Yang-ping,YIN Zhen-yu,et al.An overview on elementary mechanical behaviors,constitutive modeling and failure criterion of soils[J].China Civil Engineering Journal,2016,49(7):9-35.(in Chinese))
[3]凌华,傅华,蔡正银,等.坝料动力变形特性试验研究[J].岩土工程学报,2009,31(12):1920-1924.(LING Hua,FU Hua,CAI Zheng-yin,et al.Experimental study on dynamic deformation behaviors of dam materials[J].Chinese Journal of Geotechnical Engineering,2009,31(12):1920-1924.(in Chinese))
[4]张振东,李国英.循环荷载作用下堆石料颗粒破碎特性试验研究[J].岩土工程学报,2017,39(8):1510-1516.(ZHANG Zhen-dong,LI Guo-ying.Experimental study on particle breakage behaviors of rockfill under cyclic loadings[J].Chinese Journal of Geotechnical Engineering,2017,39(8):1510-1516.(in Chinese))
[5]张超,杨春和,白世伟.尾矿料的动力特性试验研究[J].岩土力学,2006,27(1):35-40.(ZHANG Chao,YANGChun-he,BAI Shi-wei.Experimental study on dynamic characteristics of tailings material[J].Rock and Soil Mechanics,2006,27(1):35-40.(in Chinese))
[6]SUN Q D,INDRARATNA B,NIMBALKAR S.Effect of cyclic loading frequency on the permanent deformation and degradation of railway ballast[J].Géotechnique,2014,64(9):746-751.
[7]INDRARATNA B,LACKENBY J,CHRISTIEL D.Effect of confining pressure on the degradation of ballast under cyclic loading[J].Géotechnique,2005,55(4):325-328.
[8]TANG L,YAN M H,LING X Z,et al.Dynamic behaviors of railway’s base course materials subjected to long-term low-level cyclic loading:experimental study and empirical model[J].Géotechnique,2016,67(6):1-9.
[9]冷伍明,周文权,聂如松,等.重载铁路粗粒土填料动力特性及累积变形分析[J].岩土力学,2016,37(3):728-736.(LENG Wu-ming,ZHOU Wen-quan,NIE Ru-song,et al.Analysis of dynamic characteristics and accumulative deformation of coarse-grained soil filling of heavy-haul railway[J].Rock and Soil Mechanics,2016,37(3):728-736.(in Chinese))
[10]唐开顺,谢雄耀,杨磊.圆砾土大型三轴试验力学特性研究[J].地下空间与工程学报,2014,10(3):580-585.(TANG Kai-shun,XIE Xiong-yao,YANG Lei.Research on mechanical characteristics of gravel soil based on large-scale triaxial tests[J].Chinese Journal of Underground Space and Engineering,2014,10(3):580-585.(in Chinese))
[11]张茹,何昌荣,费文平,等.固结应力比对土样动强度和动孔压发展规律的影响[J].土木工程学报,2006,28(1):101-105.(ZHANG Ru,HE Chang-rong,FEI Wen-ping,et al.Effect of consolidation stress ratio on dynamic strength and dynamic pore water pressure of soil[J].Chinese Journal of Geotechnical Engineering,2006,28(1):101-105.(in Chinese))
[12]张曦,唐益群,周念清,等.地铁振动荷载作用下隧道周围饱和软黏土动力响应研究[J].土木工程学报,2007,40(2):85-88.(ZHANG Xi,TANG Yi-qun,ZHOU Nianqing,et al.Dynamic response of saturated soft clay around a subway tunnel under vibration load[J].Chinese Journal of Geotechnical Engineering,2007,40(2):85-88.(in Chinese))
[13]INDRARATNA B,NIMBALKAR S,RUJIKIATKAMJORNC.From theory to practice in track geomechanics-Australian perspective for synthetic inclusions[J].Transportation Geotechnics,2014,1(4):171-187.
[14]MONISMITH C L,OGAWA N,FREEME C R.Permanent deformation characteristics of subgrade soils due to repeated loading[J].Transportation Research Record,1975:1-17.
[15]周文权,冷伍明,蔡德钩,等.循环荷载作用下路基粗粒土填料临界动应力和累积变形特性分析[J].铁道学报,2014,36(12):84-89.(ZHOU Wen-quan,LENG Wu-ming,CAI De-gou,et al.Analysis on characteristics of critical dynamic stress and accumulative deformation of coarse grained soil subgrade filling under cyclic loading[J].Journal of the China Railway Society,2014,36(12):84-89.(in Chinese))
[16]ERLINGSSON S,RAHMAN M.Evaluation of permanent deformation characteristics of unbound granular material using multi-stage cyclic-load triaxial tests[J].Journal of the Transportation Research Board,2014(1):178-195.
[17]LI D,SELIG E T.Cumulative plastic deformation for fine-grained subgrade soils[J].Journal of Geotechnical Engineering.1996,122(12):1006-1013.
[18]丁智,张涛,魏新江,等.排水条件对不同固结度软黏土动力特性影响试验研究[J].岩土工程学报,2015,37(5):893-899.(DING Zhi,ZHANG Tao,WEI Xin-jiang,et al.Experimental study on effect of different drainage conditions on dynamic characteristics of soft clay under different degree of consolidation[J].Chinese Journal of Geotechnical Engineering,2015,37(5):893-899.(in Chinese))
[19]田海,孔令伟,赵翀.基于粒度熵概念的贝壳砂颗粒破碎特性描述[J].岩土工程学报,2014,36(6):1152-1159.(TIAN Hai,KONG Ling-wei,ZHAO Chong,et al.Characterization of partical breakage with grading entropy on shell sand[J].Chinese Journal of Geotechnical Engineering,2014,36(6):1152-1159.(in Chinese))