白垩系砂岩宏细观冻融损伤特性试验研究

(西安科技大学,建筑与土木工程学院,陕西 西安 710054)

白垩系砂岩; 冻融损伤; 细观结构; 强度特征; 控制指标

Experimental study of the macro and micro-scopic damage of Cretaceous sandstone subjected to freeze-thaw cycles
ZHAO Tao,YANG Geng-she,XI Jia-mi,SHEN Yan-jun,CHEN Xin-nian,JIA Xiao-feng

(College of Civil and Architectural Engineering,Xi'an University of Science and Technology,Xi'an 710054,China)

Cretaceous sandstone; frost damage; microscopic structure; mechanical properties; specific surface

DOI: 10.13800/j.cnki.xakjdxxb.2019.0209

备注

为研究人工冻结对白垩系砂岩物理力学特性的影响,以粗粒、中粒砂岩为研究对象,分别开展了一次冻融前后砂岩饱和吸水率试验、氮气吸附实验; 并进行20,-30,20 ℃等不同冻结过程下的强度测试。试验结果表明:2种岩石经历冻融作用后饱和吸水率均有所增大,粗粒砂岩饱和吸水率增加幅度较大。一次冻融循环后粗粒砂岩比表面积和孔容都增大而平均孔径减小,而中粒砂岩区别于粗粒砂岩的是,其孔容呈现减小趋势。冻融作用下两种岩石单轴抗压强度和弹性模量均有不同程度的降低,粗粒砂岩单轴抗压强度和弹性模量降低幅度大于中粒砂岩。低温冻结提高了试验岩石的单轴抗压强度,粗粒砂岩单轴抗压强度提高幅度大于中粒砂岩。揭示了饱和砂岩物理力学特性劣化内在机理,指出了岩体结构特征及饱和状况是控制不同冻结过程损伤状况的主要指标。

To investigate the influence of artificial freezing on the physical and mechanical properties of Cretaceous sandstone,we measured the water absorption of saturated coarse and medium-grained sandstone samples before and after one freeze-thaw cycle,and conducted the Nitrogen adsorption experiment employing the same samples.Besides,uniaxial compressive experiments were performed in the states of room temperature(20 ℃),over freezing(-30 ℃)and after thawing(20 ℃)respectively.The results indicate that:Water absorption at saturation of both types of rock samples increase after one freeze-thaw cycle,and coarse-grained sandstone samples increase more.Specific surface area of both types of rock samples rise,while average pore size drop after one freeze-thaw cycle,pore volume of the coarse-grained sandstone increase but the medium-grained sandstone behavior oppositely.Uniaxial compressive strength and elastic moduli of both types of rock samples reduce after one freeze-thaw cycle,and coarse-grained sandstone samples experience more.Freezing significantly strengthens both types of sandstone.The above change of micro-structure and mechanical properties of sandstone after one freeze-thaw cycle can be attributed to frost damage,under the same subzero temperature,pore structure and water content are two essential factors that controls frost damage.