董英,张茂省,刘洁,张新社,冯立.西安地区含水系统释水压密效应及微结构变化[J].西北地质,2019,52(2):63-71
西安地区含水系统释水压密效应及微结构变化
Water Release Compaction Effect and Microstructure Change of Aquifer System in Xi'an
投稿时间:2019-04-04  修订日期:2019-05-02
DOI:10.19751/j.cnki.61-1149/p.2019.02.007
中文关键词:  粘性土;释水压密;CT扫描;地面沉降
英文关键词:cohesive soil;water release compaction;CT;land subsidence
基金项目:国家重点研发项目(2018YFC1504700),国家自然科学基金重点项目(41641011、41530640),中国地质调查局项目(DDT20190463、DD20160261、DD20189270)联合资助
作者单位E-mail
董英 西北大学, 陕西 西安 710069;中国地质调查局西安地质调查中心/西北地质科技创新中心, 自然资源部黄土地质灾害重点实验室, 陕西 西安 710054  
张茂省 中国地质调查局西安地质调查中心/西北地质科技创新中心, 自然资源部黄土地质灾害重点实验室, 陕西 西安 710054 xazms@126.com 
刘洁 中国地质调查局西安地质调查中心/西北地质科技创新中心, 自然资源部黄土地质灾害重点实验室, 陕西 西安 710054  
张新社 中国地质调查局西安地质调查中心/西北地质科技创新中心, 自然资源部黄土地质灾害重点实验室, 陕西 西安 710054  
冯立 中国地质调查局西安地质调查中心/西北地质科技创新中心, 自然资源部黄土地质灾害重点实验室, 陕西 西安 710054  
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中文摘要:
      西安地区诱发地面沉降地裂缝灾害最主要的因素是过量开采地下水。承压水地下水头下降引起的含水层骨架有效应力增加,粘性土释水压密一方面造成了地面沉降地裂缝灾害;另一方面引起含水层孔隙率、储水系数、渗透系数等水文地质参数的变化。笔者选取西安地裂缝最活跃的F4号地裂缝两侧钻孔岩心进行了压密CT扫描,获取了300 m以浅地层粘性土在不同压力(水头下降幅度)条件下的空隙大小的微结构变化,并建立了渗透系数与微结构变化耦合关系。结果显示:在地下水开采引起的土层应力增加过程中,大孔隙度、长孔隙度会随着压力增加而明显降低,地裂缝上盘和下盘含水层大孔隙分别降低了39.05%和9.22%,不利于水分在孔隙间运移,中小孔隙度基本保持不变或略有上升;渗透系数随压力的增加呈现出减小趋势,最大下降幅度为71.08%,且随深度增加含水层渗透系数减小幅度逐渐降低。研究结果对于科学评价和预测西安地区地面沉降地裂缝地质灾害具有指导意义。
英文摘要:
      In Xi'an city, the over-exploitation of groundwater is the most important factor for inducing land subsidence and ground fissures. The confined groundwater head increases the effective stress of the aquifer layer. The release compaction of cohesive soil water causes the land subsidence and ground fissures; it also results in the change of hydrogeological parameters, such as aquifer porosity, water storage coefficient and permeability coefficient. The borehole cores on both sides of the F4 ground fissure, served as the most active ground fissure in Xi'an city, are selected for the compacted CT scanning in this paper. Under the different pressures (head drawdown amplitude), the microstructure changes of the pores within 300m shallow clay have been obtained. And then, the coupling relationship between the permeability coefficient and microstructure change has been established. The results show that the large porosity and long porosity can decrease with the increasing pressure during the increase of soil stress caused by the groundwater exploitation. This is not conducive to the migration of water between pores. The macropores of the upper and lower aquifers of the ground fissure will decrease by 39.05% and 9.22%, respectively. The small and medium porosity is almost unchanged or only slightly increased. The permeability coefficient shows a decreasing trend with the increase of pressure. The aquifer permeability coefficient decreases with depth, the decline magnitude is gradually decreasing, and its maximum decrease is 71.08%. Thus, the research results have a guiding significance for scientific evaluation and prediction of land subsidence and ground fissure in Xi'an city.
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