圆形洞室围岩破坏模式模型试验研究

摘要

For studying the deformation and failure modes of tunnel surrounding rock systematically under different continuum media, model tests have been performed on artificial cohesive material and artificial sandy materials.Barite powder, quartz sand and vaseline are the key ingredients of the cohesive similar material.Two types of sandy material made of quartz, and quartz+barite powder are tested respectively.Pressure cell, displacement gauge and non-contact precision measurement are used to monitor the surrounding rock response after excavation, the stress and deformation of the surrounding rock induced by tunnelling and further loading.For cohesive material in the process of step loading, failure first occurs on both sides of the tunnel and then at tunnel crown.According to the displacement and stress monitoring results, in response to the increase in load, the size of plastic zone increases as well.It also reveals that once the plastic zone develops, the rate of deformation in the tunnel surrounding rock will increase.Tunnel excavation in the sandy quartz material does not possess self-stability.However, for sandy material made of quartz and barite, the tunnel remains stable after excavation.For this mixture material, with the increase in applied pressure, failure arch first appears at the tunnel crown which follows the shape of a parabola curve.The arch foot then moves towards the sides of the tunnel.Stability is achieved when it reaches the central axis of the tunnel; at this point, the collapse arch sliding surface is similar to the Platts theory.This series of model tests, which allow the observation of the deformation failure modes for lunnel under different continuum media, provide significant information for the determination of tunnel supporting parameters.%为系统研究连续介质条件下隧道围岩的破坏模式和规律,采用模型试验,针对黏性材料和砂性材料2种典型地质材料进行研究.黏性材料由重晶石、石英砂和凡士林按一定配比组成,砂性材料考虑单一石英砂材料和石英砂与重晶石混合2种形式.利用压力盒、位移计、非接触监测系统等监测隧道开挖、加载过程中围岩应力和变形情况.对黏性材料而言,在逐级加载过程中表现出先洞室两侧剪切滑移,后拱顶塌落的二次破坏模式,通过位移和应力的监测可知,随着外部荷载的增大,洞室上方塑性区范围增加,而进入塑性状态后,围岩变形速率加快.对砂性材料而言,单一石英砂材料在开挖后围岩不具有自稳能力;而采用石英砂和重晶石混合后的材料,由于颗粒级配较好,材料具有一定的自锁能力,洞室开挖后可以保持稳定,随着逐级加载,洞室顶部首先出现二次抛物线型塌落拱,然后拱脚位置向洞室两侧移动,当其发展到水平中轴线处达到稳定,此时塌落拱滑裂面与普氏拱理论类似.模型试验揭示连续介质条件下隧道围岩的破坏模式,对隧道支护参数的确定具有重要意义.