马普托大桥南锚碇工程半成岩力学特性试验研究

Experimental study on mechanical property of hypabyssal rock at south anchorage base of Maputo bridge

半成岩是一种半岩半土的特殊工程地质载体,目前针对半成岩力学特性的研究较少。依托马普托大桥南侧锚碇工程,设计可同时进行岩基承载及两相胶结面剪切的现场试验框架,开展基底细砂半成岩载荷试验和混凝土–半成岩两相胶结面剪切现场试验,获得细砂半成岩的承载和剪切力学参数,进一步深入研究和讨论半成岩变形模量的预测方法及混凝土–半成岩两相胶结面剪切破坏的形态及机制。研究表明细砂半成岩的承载性能与岩石类似,采用基于现场地质条件的经验方法可以较准确地估算半成岩的变形模量;细砂半成岩的混凝土–半成岩两相剪切具有独特的性质,其低致密性导致与混凝土形成很强的胶结作用和较明显的胶结带,从而增加了两相胶结面的粗糙程度。在预测混凝土与半成岩两相胶结抗剪强度时,需充分考虑混凝土浸入半成岩的胶结作用。研究结果为大桥锚碇设计提供了可靠的参数支持,为类似地质条件的工程提供可靠依据。

Hypabyssal rock is a special material with the property between rock and soil. Few researches have been conducted on the mechanical properties of hypabyssal rock. In this study,a field test device for conducting the load carrying tests and the shearing tests simultaneously was designed. The load carrying test of fine sand hypabyssal rock and the shear test on cementation surface of concrete and fine sand-hypabyssal rock were conducted at the south anchorage base of Maputo bridge. The load carrying and shearing parameters of the fine sand-hypabyssal rock are obtained. Based on the obtained parameters,the prediction of deformation modulus of hypabyssal rock and the morphology and mechanism of shear failure of cementation surface were further studied and discussed. The bearing property of hypabyssal rock was found to be similar to rock. The empirical methods based on the on-site geological conditions can be used to estimate the deformation modulus accurately. However,the shear property of the cementation surface is different from the rock. Its low compactness leads to the strong cementation with the concrete and form an obvious adhesive zone. The cementation should be fully considered when the shear strength of the hypabyssal rock-concrete cementation surface is evaluated.