Abstract The objective of this study is to determine the effect of cyclic loading under pre-peak condition on shearing behavior of fractures in Phra Wihan sandstone, primarily to improve an understanding of the stability conditions of slope embankments along roadways and railways in the north of Thailand where seismic activities have often occurred. The fractures were artificially made in the laboratory by tension inducing method and cyclically sheared under forward to fully backward loading paths with constant normal stresses between 1 and 4 MPa. Two cyclic loading conditions were used on separate sets of specimens: constant stress amplitude and constant displacement amplitude. Fifty shear cycles were applied. The results indicated that the pre-peak cyclic loading under both loading conditions slightly reduce shear strengths and stiffness of the sandstone fractures due to the degradation of the second order fracture asperities. Fracture roughness notably reduced particularly under large shear stress and displacement amplitudes due to the deposition and packing of rock power. The subsequent monotonic loading performed after cyclic loading showed further reduction of fracture roughness due to the degradations of the first order asperities.

中文翻译：

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砂岩裂缝在前后峰前循环荷载作用下的摩擦行为

摘要 本研究的目的是确定峰前条件下循环荷载对 Phra Wihan 砂岩裂缝剪切行为的影响，主要是为了提高对泰国北部公路和铁路沿线边坡路堤稳定性条件的了解。地震活动频繁发生的地方。裂缝是在实验室中通过张力诱导方法人工制造的，并在正向到完全反向加载路径下循环剪切，恒定法向应力在 1 到 4 MPa 之间。两种循环加载条件用于不同的试样组：恒定应力幅和恒定位移幅。应用了五十个剪切循环。结果表明，两种加载条件下的峰前循环加载都会轻微降低砂岩裂缝的剪切强度和刚度，这是由于二级裂缝凹凸不平的退化。由于岩石粉末的沉积和堆积，裂缝粗糙度显着降低，特别是在大剪切应力和位移幅度下。由于一阶凹凸不平的退化，在循环加载之后进行的后续单调加载显示断裂粗糙度进一步降低。