片麻岩风化程度及其声发射规律试验研究

Weathering Degree of Gneisses and Their Acoustic Emission Characteristics

作为建筑地基使用的泰山片麻岩,埋藏浅、区域特征明显,其风化特性对土木工程稳定性的影响广泛而复杂。应力-应变关系试验发现,5组片麻岩试件的A、B、C-D和E组分别隶属于未风化、中等风化、强风化和全风化4种风化程度。力学性质试验时同步检测不同风化程度片麻岩的声发射信号,发现随片麻岩风化程度的提高,振铃计数率呈明显下降趋势;未风化及中等风化片麻岩的振铃计数率最高可达2 500次/s,具有能量累积并集中释放的特点,岩石脆性特征较明显;强风化片麻岩的振铃计数率平均约200次/s,声发射信号密集,岩石具有典型的延性特征;全风化片麻岩的平均振铃计数率仅约15次/s,声发射信号离散、无规律,岩石已等同于散体介质;得到了部分片麻岩风化程度与声发射之间的量化规律。建立的片麻岩风化程度与声发射关系,可应用于指导风化片麻岩地基的处理,寻求匹配的地基置换材料。

As a foundation building material,Taishan gneiss was shallowly buried and had obviously regional characteristics. The influence of weathering degree of gneiss on the stability of civil engineering was extensive and complex. Test on the relationship of strain and stress presents that five groups of gneiss specimens have been subjected to no weathering,middle weathering,strong weathering and full weathering respectively. Synchronous acoustic emission signals of gneisses with different weathering degrees have been tested in mechanical test,which indicates that ringing counting rates present evident downtrend with the increase of weathering grades of gneiss. The highest ringing counting rate of no weathering and middle weathering gneisses can reach 2 500 per second and their energy is cumulative and releases centrally,which determines their obvious brittleness. Strong weathering gneiss is of typical ductility and its acoustic emission signals are concentrated,whose average ringing counting rate is about 200 per second. That average ringing counting rate of full weathering gneiss is only 15 per second and its discrete and irregular acoustic emission signals indicate that it is the same as a disperse medium. Partial quantization rules between weathering degree of gneiss and its acoustic emission signal have been obtained. The established relationship between weathering degree of gneiss and its acoustic emission signal may be useful for the treatment of weathered gneiss and looking for the replacement materials of the foundation.