A study of the cracking mechanism of ground fissures under the action of active faults
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摘要: 地裂缝的成因机理争论不断，笔者认为活动断层与全新世浅表层开裂两者之间的联动机制为主要原因之一。文章以华北平原典型地裂缝为例，通过详尽地面调查、资料分析总结，结合地球物理勘察、槽探揭露和钻探等多种技术方法，得到以下几点认识：（1）依据全新世浅表层开裂形态特征，可将华北平原地裂缝划分为全新世节理裂隙型地裂缝和全新世活动断层型地裂缝。（2）节理裂隙型地裂缝开裂的外部条件是华北平原地下水位下降，疏干的松散含水层是地表水沿节理裂缝下渗后的储存场所，是产生渗透压力的原因；而活动断层是产生该类地裂缝的内部因素，两者缺一不可；活动断层型地裂缝实质是全新世活动断层。（3）节理裂隙型地裂缝主要特征是地表局部塌陷、间断性、地表无高差等；活动断层型地裂缝主要特征是连续性强，地表断距明显；地表断距是两种类型地裂缝的最主要区别特征。本文首次以构造活动断层与全新世浅表层开裂两者之间的联动机制为研究线索，阐述了构造活动断层在地裂缝形成过程中的具体作用，厘清了地下水位下降所扮演的“角色”，为城市规划建设提供了地质依据和建议。Abstract: There is continuing controversy about the genesis mechanism of ground fissures. The authors believe that the linkage mechanism between active faults and Holocene shallow surface fissures is one of the main reasons. The typical ground fissures in the North China Plain are examined, and detailed ground investigation, data analysis and summary are carried out, combined with geophysical survey, trench exploration and drilling and other technical methods. The results show that (1) according to the characteristics of surface morphology, ground fissures in the North China Plain can be divided into two types: Holocene jointed fissures and Holocene active fault fissures. (2) The external condition of joint-fissure type of ground fissure cracking is the decrease in groundwater level in the North China Plain, and the dried loose aquifer is the storage place of surface water after seeping down along joint fissures, which is the cause of seepage pressure, while the active fault is the internal factor of producing ground fissures, both of which are indispensable. Active fault type of ground fissures are essentially Holocene active faults. (3) The main characteristics of the jointed fissure type of ground fissures are local surface subsidence, discontinuity, no-difference in surface height, etc. The main characteristics of the active fault type ground fissures are strong continuity, obvious surface fault distance, which is the main distinguished feature between the two types of ground fissures. (4) The linkage mechanism between tectonic active faults and Cenozoic shallow surface fissures is studied for the first time in this paper. The clue elaborates the specific role of tectonic active faults in the formation of ground fissures, clarifies the “role” of groundwater level decline, and provides geological basis and suggestions for urban planning and construction.
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Key words:
- ground fissures /
- active faults /
- Holocene Epoch /
- joint fracture /
- cracking mechanism /
- North China Plain
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