红层泥岩三轴膨胀力的试验研究

An experimental study of the triaxial expansion force of red-bed mudstone

针对现有规范中红层泥岩膨胀力测试结果偏小问题,自主研制了膨胀性岩石三轴膨胀力测试装置。采用先放试样后加约束的方式克服了岩石与容器壁有释放变形空隙的局限性,解决了膨胀力测试结果偏小的问题。通过膨胀土和红层泥岩三轴膨胀力的测试研究,检验了三轴膨胀力测试装置的合理性和有效性,初步总结了红层泥岩三轴膨胀力的变化规律。研究结果表明:三轴膨胀力测试装置及其测试方法能够克服传统固结仪试验方法的局限性,具有较好的实用性,可以适用于膨胀土和膨胀岩三轴膨胀力的测试;红层泥岩三轴膨胀力多数是在MPa的量级,传统固结仪测试的膨胀力多数是kPa量级,更新了现有红层泥岩膨胀力较小的认识;通过对试验结果的分析和膨胀后试样的观察,发现红层泥岩的膨胀机制与膨胀土的膨胀机制是不同的;红层泥岩主要是新鲜岩石表层吸水膨胀、泥化崩解,泥化层剥蚀后,新鲜面再次吸水膨胀、泥化崩解,这是一个逐层循环膨胀的过程。

Aiming at the problem that the swelling force of the red-bed mudstone is smaller than the theoretical value according to the code,this paper develops a triaxial swelling force device for the swelling rock.By placing the sample first and then restraining it,the deformation gap between the rock and the container’s wall is overcome.Through the experimental research of the triaxial expansion force of expansive soil and red-bed mudstone,the rationality and effectiveness of the triaxial expansion force device are verified.According to the experimental test results of the typical red-bed mudstone samples in Sichuan,the changes of the swelling force of the muddy swelling rock is preliminarily summarized.The research results show that the triaxial expansion force device and its test method can overcome the limitations of the existing method of consolidation instrument test.It is simple to operate,is of good practicability,and can be applied to the triaxial expansion force test of expansive soil and expansive rock.The experimental results of comparison of triaxial expansion force and uniaxial expansion force show that the triaxial expansion force of the red-bed mudstone is mostly in the magnitude of MPa,and the expansion force tested by the consolidation instrument is mostly in the magnitude of kPa.Through the analysis of the test results and the observation of the sample after expansion, it is found that the expansion mechanism of the red-bed mudstone is different from that of the expansive soil. The red-bed mudstone is mainly the surface layer of fresh rock that absorbs water and swells and disintegrates. After the surface layer is denuded, the fresh surface absorbs water again to swell and disintegrate. This is a cyclic expansion process layer by layer.