Rapid evaluation of durability of rocks subjected to freezing and thawing cycle with an accelerating deterioration test

为了快速评价冻融循环下岩石的耐久性，提出了一种新的试验方法--“搭接法”。在此基础上，研究了冻融循环下岩石耐久性与岩石物理性质的关系。主要研究结果如下：采用搭接法和ASTM推荐的标准方法对岩石进行了冻融试验。用这两种方法测定了岩石的劣化率。因此，裂纹萌生在研磨方法比在标准方法更快。结果表明，研磨法的早期劣化速度比标准法快。然而，裂纹扩展速率和断裂循环数在标准方法中比在研磨方法中更快。在标准方法中，试样的含水量在试验过程中逐渐增加，而在研磨方法中，试样的含水量几乎是恒定的。通过对9种岩石进行冻融试验，研究了岩石60次循环失重与吸水系数和抗拉强度的关系。失重随吸水系数的增加和抗拉强度的降低而增加。结果表明，失重率与吸水系数呈正相关，与抗拉强度呈负相关。抗拉强度大于2 MPa的岩石试件不产生裂纹。这些结果表明，岩石在冻融循环作用下的耐久性可以用其吸水系数或抗拉强度来评价

A new testing method referred to "lapping method" was developed in order to evaluate quickly durability of rocks subjected to freezing and thawing cycles. Then, the relationship between the durability of rocks subjected to freezing and thawing cycles and some physical properties was investigated. Main results are summarized as follows.Freezing and thawing tests were conducted on rocks with the lapping method and a standard method suggested by ASTM. Deterioration rate of rocks was examined in these two methods. Consequently, crack initiation in the lapping method was faster than that in the standard method. It is cleared that the deterioration rate in the lapping method is faster than that in the standard method in the early stage. However, crack propagation rate and number of cycles to breaking was faster in the standard method than in the lapping method. Water content of the specimen gradually increased during test in the standard method, but it is almost constant in the lapping method. This fact may attribute to crack propagation and breaking.Freezing and thawing tests were carried out with nine kinds of rocks to study a relationship between weight loss at 60th cycles and coefficient of water absorption or tensile strength. The weight loss shows an increase with an increase in the coefficient of water absorption and with a decrease in tensile strength. It was found that the weight loss is positively correlated with the coefficient of water absorption, and negatively correlated with the tensile strength. No Crack initiation can be observed in rock specimens when its tensile strength is higher than 2 MPa. These results indicate that durability of rocks subjected to freezing and thawing cycles can be estimated with their coefficient of water absorption or their tensile strength