断续双裂隙砂岩三轴卸荷蠕变特性试验及损伤蠕变模型

Experimental study on the triaxial unloading creep characteristics of stone with two pre-existing cracks and its damage creep model

为研究卸荷条件下裂隙岩体的蠕变特性,以通过对砂岩切割并充填水泥砂浆制备的裂隙试样为对象,开展了恒轴压分级卸围压三轴卸荷蠕变试验。试验结果表明:试件在破坏时对应应力差最小的是缓缓和陡缓裂隙组合岩体,其次为陡陡裂隙组合岩体和完整试样;从变形特点来看,相同应力状态下,瞬时应变与蠕应变从大到小的顺序依次均为缓缓、陡缓、陡陡裂隙组合岩体和完整岩石。采用元件模型对各试件不含加速蠕变阶段的变形进行的拟合显示,可采用同一形式的本构模型对裂隙岩体和完整试样进行描述。根据这一结论提出了基于Lemaitre应变等效原理和Sidoroff能量等价原理的裂隙岩体损伤蠕变模型,并与室内试验结果进行了对比与分析。该模型可通过完整岩石蠕变模型参数推导裂隙岩体蠕变模型参数,从而建立了完整岩石与裂隙岩体间的关系。

In order to understand the unloading creep characteristics of fractured rock,the sandstone specimens with two pre-existing cracks were prepared,then the unloading creep test with the axial pressure remaining stationary and the lateral stress unloading gradually was performed in laboratory. The results show that for the deviator stress at failure,the minimum value was found for low-low angle type specimen and high-low angle type specimen,followed by high-high angle type specimen and intact sandstone. Under the same stress level,the maximum value of instantaneous strain and creep strain were found for low-low angle type specimen,followed by high-low angle type specimen,highhigh angle type specimen and intact sandstone. The traditional element models were presented for the creep curves of all specimens,the results show that the intact specimens and fractured specimens have the same form of constitutive model,just the parameters are different. Based on the research results,the fractured rock mass damage creep constitu-tive models were put forward by using the equivalent strain and energy equivalent principle,and then compared with the laboratory tests results. The relationship between the intact rock and fractured rock mass was established by these fractured rock mass damage creep constitutive models.