高温高压下煤超微构造的变形特征

DEFORMATION CHARACTERISTICS OF SUPERMICROSTRUCTURES OF COAL UNDER THE CONDITION OF HIGH TEMPERATURE AND CONFINING PRESSURE

本文通过不同温、压实验条件下，不同煤级煤的应力－应变曲线及超微变形构造特征分析，深入探讨了不同煤化程度煤的变形行为及其影响因素。阐明了高温高压和差异应力作用是促使煤结构由无序向有序方向转化，使大分子结构有序畴和定向性增大的重要因素。论述了温度和压力在不同的煤级和不同的实验条件下，具有不同的作用。在中煤级阶段，虽然围压的增大可在一定程度上提高煤的强度，但温度的影响更为重要。较高煤级在小应变阶段，温度起主导作用；而到了大变形阶段，围压的作用又逐渐上升到主导地位。在整个变形过程中，定向压力都是不容忽视的重要因素。

According to the analysis of stressstrain curves and deformation characteristics of supermicrostructures of different rank coals(Ro,max=1.18%-4.11%) that deformed under different conditions of temperature and confining pressure(T=200-700℃, pc=250-650MPa) the paper inquired deep into the deformational behaviors of coals of different degrees of coalification and their influence factors. It is discussed that temperature and pressure have different actions to different rank coals under different experimental conditions. The experimental results showed that strength of all the coal samples decreased along with increasing temperature. It made deformation of coals easier. In contrast, increase of pressure may make coal strength heightened. Although increase of confining pressure may enhance intensity of coals,action of temperature is more important in stage of medium rank coals. Temperature takes a leading effect in stage of less strain of higher rank coals,but action of confining pressure gradually rises into a leading effect in stage of larger strain. The important action of stress can not be ignored in the whole deformation process of coals, especially in aspects of transformation of coal structures from disordering into ordering and increase of the order domain and orientation of megamolecule structures, it is the more important factor. But the ordering evolution of coal structutres is not the same in different rank coals and under the action of different temperature ,confining pressure and differential stress. The ordering domain increases slowly when the coal rank is relatively low. The extension degree increases quickly and the orientation is obvious and the megamolecule structures similar to microcolumn graphite and winkle graphite may form locally. When the coal ranks are higher, the basic structural units are more concentrated and the ordering develops very quickly. The wormy basic structural units, which have more extension degree, may take place. Moreover, the structure of closed rings that is composed of original aromatic clustrs may further be pressed flat. The long axes of the rings are nearly parallel to the strength direction of the basic structural units and the orientation is more obvious. 