大跨度采空影响顺倾构造山体侧向变动的复合机理

采空区地表山体侧向变动,不同于一般天然山坡,也与采空区一般上覆岩层的变形破坏有异;它是二者复合机理的效应。本文在分析考察了毗邻电厂的横山顺倾构造山体,剖析了地下采空情况后认为,山体侧向变动中,软弱夹层有决定性作用;变动范围、速率与规模,与地下采空有关。从而又利用地质力学模型试验和数值模拟,探索了采动引起山体应力场及变动规律。结果表明,山体岩层的变形、位移、破坏,由直接顶板向地表发展;采空坍陷诱发了软弱夹层的蠕滑,则产生山体侧向滑移;电厂区地表隆起变形是山体侧向滑移挤压地基土的反映。通过现场实际调究、变形观测资料分析与数值模拟和模型试验的对比研究,提出了“坍落拱梁”的成生效应、挤压蠕滑效应、失稳效应;揭露了顺倾构造山体在采空影响下,具有地表、地下的“复合临空面”的“复合应力场”中“复合变动”的“复合机理”;并提出这种山体侧向变动机理的典型地质模式,借以论证山体稳定性。

COMPOSITE MECHANISM OF LATERAL MOVEMENT OF THE SLOPE ON A DOWN DIP STRUCTURE MOUNTAIN ASSOCIATED WITH THE UNDERGROUND EXCAVATION ABOUT LONG-SPAN

The slope movement above the mined-out area is different from the deformation and failure of general slope and overlying strata in mine area. It is an effect of both the site movements and mechanisms. This study leads to establish a new research field of mountain Environmental Engineering Geology. Hengshan slope adjacent to a power plant forms a low-angle and downdip structure mountain, and there are several coal seams beneath it. Based on analysis of the structural characteristics of low-angle rock layer, this paper deals with the mechanical properties of weak interlayers on the slope. It is considered that the weak interlayers play a leading role in the lateral movement of the slope. According to detailed field investigation and analysis of displacement data obtained, it is founded that the deformation of rock mass of the slope is mainly controlled by underground mined-out area, and collapse as well as the creeping of the rock mass on the pre-slope toward the landsurface occur. Furthermore, slope deformation process and characteristics associated with underground mine collapse were studied using geomechanical modelling and elastic-plastic finite element method. The regularity of stress change within the slope caused by mine collapsing beneath the slope is analysed. It is showed that the deformation, displacement and failure of rock formations are through the overlying strata to the landsurface of the slope, and that the weak interlayer creeping induced by mine collapsing beneath the slope leads to the slope lateral movement. The surface doming of power plant area is caused by pre-slope rock mass pushing against the basement soil. By comparing the modelling results to real deformation and displacement data and geological indications, the collapse arching effect, the effect of additional push creeping and the damaging effect of collapse arching which were induced by underground coal mining, are analysed in detail and proposed. Thereby, this paper proposed also the "composite mechanism" of composite movement within the "composite stress field" and "composite boundary surfaces", associated with the collapsing of the overlying strata about the slope downdip structure mountain. The typical geological model for the lateral movement of low-angle rock formation on the slope has been put forward.