温度-渗流耦合作用下砂岩卸荷蠕变试验研究

Experimental study on unloading creep of sandstone under temperature-seepage coupling conditions

巷道/隧道开挖后环境因素(温度、水)及耦合作用会改变围岩的卸荷蠕变性质,从而对围岩稳定及施工现场的安全维护产生威胁。为研究温度、渗流水及耦合作用对砂岩卸荷蠕变特性的影响,采用自主设计的温度控制系统和改良的孔隙水传导试件密封装置,开展了砂岩试件(φ50 mm×100 mm)三轴卸荷蠕变试验。研究发现:(1)在卸围压后的300 min蠕变时长内,轴向压缩及径向扩容蠕变速度先逐渐增加后放缓,以径向蠕变为主。(2)温度降低(65°C→30°C)最终会导致干燥及饱和试件的轴向蠕变量增加,而径向蠕变量减小。(3)随着渗流水压增加,轴向蠕变量减小,渗流水压增加对开挖后轴向蠕变起到抑制作用;而径向蠕变量显著增加,扩容现象明显,渗流水压增加对径向蠕变起到促进作用。(4)随着渗流水压增加,轴向卸荷蠕变速率减小,径向卸荷蠕变速率增大。温度-渗流耦合作用下,卸荷蠕变速率曲线分为衰减阶段和稳定阶段,衰减阶段变形量占主导地位。径向蠕变速率高于轴向,且径向蠕变速率的波动幅度较小,趋于稳定的速度更快。研究结果可为深部地下工程围岩稳定评价提供参考。

Environmental factors(such as temperature and water)and their coupling effects will change the unloading creep properties of surrounding rock after tunnel excavation,threatening the stability of surrounding rock and the safety maintenance of construction sites.To analyze the effects of temperature,seepage flow,and their coupling on the creep characteristics of sandstone unloading,the triaxial unloading creep test was carried out on the sandstone specimen(φ50 mm×100 mm)by using the self-designed temperature control system and the improved pore water conduction specimen sealing device.The results show that during the creep time of 300 min after unloading the confining stress,the axial compression and radial expansion creep speed increase gradually and then slow down.The strain is mainly radial creep.The decrease in temperature leads to the increase in axial creep deformation and the decrease in radial creep deformation of the dry and saturated specimens.With the increase in seepage water pressure,the axial strain reduces,and the seepage water pressure suppresses the axial creep deformation,while the radial strain increases significantly,and the expansion phenomenon is obvious.Seepage water pressure promotes radial creep deformation.With the increase of seepage water pressure,the axial unloading creep rate decreases and the radial unloading creep rate increases.Under the coupling effect of temperature and seepage,the creep rate curve of unloading is divided into the attenuation stage and the stable stage,and the deformation in the attenuation stage is dominant.The radial creep rate is higher than the axial creep rate,and the fluctuation amplitude of the radial creep rate is small,which reaches stability fast.This study can provide scientific information for the stability evaluation of surrounding rock in deep underground engineering.