季冻区矿山排土场粗粒土冻融界面剪切性能研究
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摘要
随着我国西部矿产资源的大力开发,季节冻融作用对于高寒高海拔地区矿山排土场的稳定性影响问题日益突出。以西藏某高海拔多金属矿山排土场为研究对象,利用可控温大型直剪仪开展了排土场粗粒土在全融状态下和冻融交界面的剪切试验,并考察砾粒组含量对两种状态下粗粒土剪切强度的影响。结果表明:对于全融粗粒土,其剪切应力—剪切位移曲线呈现应变硬化特征,而冻融交界面剪切应力—剪切位移曲线呈现应变软化特征。同一砾粒组含量条件下,相对于融土,冻融交界面抗剪强度约是其2倍,主要原因体现在两方面:一是冻融界面处冰的胶结作用增加了土体的粘聚强度,试验条件下这一贡献量值约在50～60 kPa;二是冻融界面处水分的润滑作用有所减弱导致滑动摩擦增加,且粗颗粒表面的冰包裹作用增强了颗粒之间脱离咬合的咬合摩擦,因此其内摩擦强度同样大于融土。随砾粒组含量增加,融土、冻融界面黏聚力显著减小,而内摩擦角显著增加,但相较于融土,冻融界面处黏聚力减小幅度较小而内摩擦角增加幅度较大。
With the development of mineral resource exploitation in western China,the seasonal freezing-thawing effect has become more and more important to the stability of mine dump in high-altitude and cold regions. Taking a polymetallic mine in Tibet as the object,a series of shear tests on coarse-grained soils from dump of the mine at a freeze-thaw interface and under full thawed state were carried out using a large direct shear apparatus with temperature control. The effect of gravel particles content on shear strength of coarse-grained soils was considered during the test design. The results show that the shear stress-shear displacement curve of coarse soils under full thawed state performs as strain hardening,while that at freeze-thaw interface shows strain softening characteristics. Under the same content of gravel particles,the shear strength of freeze-thaw interface is approximately 2 times as much as that of full-thawed soils. The reason of this phenomenon lies in tow aspects. Firstly,the ice cementation increases the cohesive strength of the soil interface. Under the test condition,the cohesive strength increased by ice cementation is approximately 50～60 kPa. Secondly,the lubrication of water at the freeze-thaw interface is weakened,which leads to the increase of sliding friction. Moreover,the ice encapsulation on the surface of coarse particles enhances the occlusal friction between particles,so the internal friction strength of coarse particles at freeze-thaw interface is also greater than that of the thawed soils. With the increase of gravel particles content,the cohesive forces at both the freezethaw interface and the thawed soils decrease,while the internal friction angles increase. Compared with the thawed soils,the cohesive force of the freeze-thaw interface decreases relatively slowly and the internal friction angle increase quickly.
With the development of mineral resource exploitation in western China,the seasonal freezing-thawing effect has become more and more important to the stability of mine dump in high-altitude and cold regions. Taking a polymetallic mine in Tibet as the object,a series of shear tests on coarse-grained soils from dump of the mine at a freeze-thaw interface and under full thawed state were carried out using a large direct shear apparatus with temperature control. The effect of gravel particles content on shear strength of coarse-grained soils was considered during the test design. The results show that the shear stress-shear displacement curve of coarse soils under full thawed state performs as strain hardening,while that at freeze-thaw interface shows strain softening characteristics. Under the same content of gravel particles,the shear strength of freeze-thaw interface is approximately 2 times as much as that of full-thawed soils. The reason of this phenomenon lies in tow aspects. Firstly,the ice cementation increases the cohesive strength of the soil interface. Under the test condition,the cohesive strength increased by ice cementation is approximately 50～60 kPa. Secondly,the lubrication of water at the freeze-thaw interface is weakened,which leads to the increase of sliding friction. Moreover,the ice encapsulation on the surface of coarse particles enhances the occlusal friction between particles,so the internal friction strength of coarse particles at freeze-thaw interface is also greater than that of the thawed soils. With the increase of gravel particles content,the cohesive forces at both the freezethaw interface and the thawed soils decrease,while the internal friction angles increase. Compared with the thawed soils,the cohesive force of the freeze-thaw interface decreases relatively slowly and the internal friction angle increase quickly.
引文
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[17]王光进,杨春和,张超,等.超高排土场的粒径分级及其边坡稳定分析研究[J].岩土力学,2011,32(3):905-913.Wang Guangjin,Yang Chunhe,Zhang Chao,et al.Research on particle size grading and slope stability analysis of super-high dumping site[J].Rock and Soil Mechanics,2011,32(3):905-913.
[18]凌华,傅华,韩华强.粗粒土强度和变形的级配影响试验研究[J].岩土工程学报,2017,39(S1):12-16.Ling Hua,Fu Hua,Han Huaqiang.Experimental study on effects of gradation on strength and deformation of coarse-grained soil[J].Chinese Journal of Geotechnical Engineering,2017,39(S1):12-16.
[2]何芳,徐友宁,陈华清,等.西北地区矿山地质灾害的现状及其时空分布特征[J].地质通报,2008,27(8):1245-1255.He Fang,Xu Youning,Chen Huaqing,et al.Current situation and spatial and temporal distribution characteristics of geological hazards in Northwest China[J].Geological Bulletin of China,2008,27(8):1245-1255.
[3]刘传正.中国崩塌滑坡泥石流灾害成因类型[J].地质论评,2014,60(4):858-868.Liu Chuanzheng.Genetic types of landslide and debris flow disasters in China[J].Geological Review,2014,60(4):858-868.
[4]刘传正.关注冰雪冻融引发的崩塌滑坡灾害[J].水文地质工程地质,2014,41(2):I0001.Liu Chuanzheng.Concerned about the collapse and landslide caused by freezing and thawing[J].Hydrogeology&Engineering Geology,2014,41(2):I0001.
[5]崔鹏,陈晓清,程尊兰,等.西藏泥石流滑坡监测与防治[J].自然杂志,2010,32(1):60-65.Cui Peng,Chen Xiaoqing,Cheng Zunlan,et al.The landslide debris flow monitoring and control in Tibet[J].Chinese Journal of Nature,2010,32(1):60-65.
[6]王超.季冻区哈大高铁边坡冻融滑塌机理研究[D].哈尔滨:哈尔滨工业大学,2014.Wang Chao.Research on Freeze-thaw Slumping Mechanism of Harbin-Dalian High-speed Railway Slope in Seasonal Frozen Region[D].Harbin:Harbin Institute of Technology,2014.
[7]Lai Yuanming,Li Chuangyang,Gao Zhihua,et al.Stochastic damage constitutive model for warm frozen soil under uniaxial compression and strength distribution[J].Journal of Glaciology and Geocryology,2007,29(6):970-976.
[8]Tsytovich N A.The Mechanics of Frozen Ground[M].translated by Zhang Changqing,Zhu Yuanlin.Beijing:Science Press,1985
[9]徐学燕,丁靖康,娄安金.冻融界面土体的长期抗剪强度指标确定[J].哈尔滨建筑工程学院学报,1992(03):37-42.Xu Xueyan Ding Jingkang,Lou Anjin.Determining the long term shear strength at the frozen-unfrozen interface[J].Harbin Architecture&Civil Engineering.Institute,1992(03):37-42.
[10]佟治权.砂粘土和粘砂土冻融交界面的抗剪强度试验报告[C]∥青藏铁路多年冻土科研成果论文集.北京:铁道部科学技术司,2003:111-122.Tong Zhiquan.Test report of shear strength at the interface of freezethaw interface between sand clay and clay soil[C]∥Qinghai-Tibet Railway Permafrost Research Achievement Research Papers.Beijing:Department of Science and Technology,Ministry of Railways,2003:111-122.
[11]葛琪,李京子,武鹤,等.寒区公路土质边坡冻融界面的抗剪强度试验[J].交通科技与经济,2017,19(1):39-41.Ge Qi,Li Jingzi,Wu He,et al.Experimental study on shear strength deterioration of the freezing and thawing interface of soil slope in seasonal frozen regions[J].Technology&Economy in Areas of Communications,2017,19(1):39-41.
[12]邓爱平.基于冻融界面对路基土体抗剪强度的影响研究[J].湖南交通科技,2017,43(3):91-93.Deng Aiping.Research on shear strength of subgrade soil based on freeze-thaw interface[J].Hunan Communications Science and Technology,2017,43(3):91-93.
[13]程永春,葛琪,何锋.季冻区土质边坡滑动界面临界深度的试验研究[J].岩土力学,2010,31(4):1042-1046.Cheng Yongchun,Ge Qi,He Feng.Experimental research on critical depth of slip surface of soil slopein seasonal frozen area[J].Rock and Soil Mechanics,2010,31(4):1042-1046.
[14]杨让宏,朱本珍.冻融交界面变化对于多年冻土区斜坡路堤稳定性的影响分析[J].兰州交通大学学报,2010,29(3):1-6.Yang Ranghong,Zhu Benzhen.A Freeze-thaw Interface Analysis of the Influence of the Slope Embankment Stability in Permafrost Regions[J].Journal of Lanzhou Jiaotong University,2010,29(3):1-6.
[15]吴海燕.模拟冻融界面的冻土模型实验研究[D].成都:西南交通大学,2007.Wu Haiyan.Experimental Study of Frozen Soil Model with a Simulative Frost-Thawing Interface[D].Chengdu:Southwest Jiaotong University,2007.
[16]谢学斌,潘长良.排土场散体岩石粒度分布与剪切强度的分形特征[J].岩土力学,2004,25(2):287-291.Xie Xuebin,Pan Changliang.Fractal characteristics of size distribution and shear strength of bulky rock material in waste pile of mines[J].Rock and Soil Mechanics,2004,25(2):287-291.
[17]王光进,杨春和,张超,等.超高排土场的粒径分级及其边坡稳定分析研究[J].岩土力学,2011,32(3):905-913.Wang Guangjin,Yang Chunhe,Zhang Chao,et al.Research on particle size grading and slope stability analysis of super-high dumping site[J].Rock and Soil Mechanics,2011,32(3):905-913.
[18]凌华,傅华,韩华强.粗粒土强度和变形的级配影响试验研究[J].岩土工程学报,2017,39(S1):12-16.Ling Hua,Fu Hua,Han Huaqiang.Experimental study on effects of gradation on strength and deformation of coarse-grained soil[J].Chinese Journal of Geotechnical Engineering,2017,39(S1):12-16.