A study of the transfer law of formation stress and displacement induced by active ground fissures
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摘要: 以西安地裂缝典型地段为研究对象，建立基于实际地裂缝活动方式的地质力学模型，通过FLAC3D数值模拟，研究地裂缝活动作用下地层应力和位移传递规律。结果表明：地裂缝活动作用下，地表竖向沉降变形曲线近似呈反“S”形，表现出“牵引挠曲”现象，水平位移曲线出现明显波峰现象；随着地裂缝位错量的增大，地表竖向和水平位移均逐渐增大；基于地裂缝活动引起的地表变形平均倾斜值，确定了地裂缝带影响区范围为上盘21 m和下盘13 m。地裂缝活动引起两侧地层断距由深部到浅表部逐渐减小，具有明显的变形传递衰减特征，且地层断距随埋深的变化曲线可近似概化为一个四次多项式方程。地裂缝活动导致上盘地层出现应力降低区，下盘地层出现应力增强区，上盘应力降低区范围大于下盘应力增强区，且上、下盘应力变化范围随着位错量的增大均逐渐增大。地裂缝活动作用下地裂缝两侧地层应力影响区随地层埋深的增大而增大，其与埋深之间关系近似满足三次多项式方程。研究结果可为盆地断裂控制型地裂缝发育区的工程防灾减灾提供科学依据。Abstract: Based on the typical zones of ground fissures in Xi’an, the geological mechanics model of the actual activity mode of ground fissures is established. The transfer law of formation stress and displacement under the action of active ground fissures is studied with the FLAC3D numerical simulation method. The results show that under the action of active ground fissures, the curves of ground vertical displacement exhibit an approximate reverse-S shape, indicating the phenomenon of traction deflection. The curves of horizontal displacement appear the phenomenon of an obvious peak. The vertical and horizontal displacement gradually increases with the settlement of the hanging wall of the increasing ground fissure. Based on the average ground deformation tilt values induced by ground fissures, the affected zone range of ground fissure belts is determined, which is 21 m in the hanging wall and 13 m in the football from ground fissures, respectively. The fault throw on both sides of the formation induced by ground fissures gradually decreases with the depth from deep to shallow surface, which is characterized by the obvious deformation transfer and attenuation. The curves of fault throw of formation variation with the buried depth can approximately be expressed using a quartic polynomial equation. Under the action of active ground fissures, there appears a stress reduced area in the hanging wall, which is bigger than the stress enhanced area in the footwall. The stress variation range in the hanging wall and the football gradually increase with the increasing settlement of the hanging wall. The relationship between the affected zone of the formation stress on both sides of ground fissures, which gradually increases with the increasing buried depth, and the buried depth approximately satisfies a cubic polynomial equation. The results can present a scientific basis for disaster prevention of active ground fissure zones controlled by basin faults.
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Key words:
- ground fissure /
- formation stress /
- ground deformation /
- fault throw of formation /
- affected zone range
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