三峡库区巫山移民新城址松散堆积体成因机制研究

FORMATIONG MECHANISM OF LARGE-SCALE LOOSE SEDIMENT AT THE RELOCATION SITES OF WUSHAN COUNTY ON THE THREE-GORGES

以巫山移民新城址松散堆积体成因类型为例 ,对三峡库区分布较广的松散堆积体进行了研究。通过对大量新开挖剖面的调查测绘 ,在许多地段发现了堆积与基岩之间的滑坡主滑带 ,说明了在该区分布较广的松散堆积体成因具有复合性。它是构造和岩溶作用前提下形成的滑坡体、崩塌体、泥石流堆积体和岩溶坍陷堆积体。运用高分辨率浅层地震勘探揭示堆积体发育深度可达 40 m至 6 0 m ,通过面波测试可按波速将之划分为三层。最后 ,建立了松散堆积体形成演化的概念模型 ,并运用目前最新版本的离散元软件 (UDEC3.0 )对其中最为重要的一种类型滑崩堆积体的形成演化过程进行了模拟。结果表明 ,该区的层状岩体在长江河流下切过程中 ,形成了区域性的卸荷松动 ,而在岩体下部形成压碎张裂带 ;地下水沿卸荷拉裂带渗入 ,并与压裂带贯通 ,形成了岩溶发育带 ,为滑坡、崩塌、塌陷等表生改造提供了条件。其形成演化可划分为能量积累、断裂体系形成、回弹变形与卸荷破裂阶段。

Investigation, identification and evaluation of the large scale loose deposits sediments at the relocation sites of Wushan County on the Three Gorges are discussed . A large number of the excavated sections show a complex accumulation of the sediments formed by tectonic process and karstification, and reveal a sliding zone between the loose deposit and bed rock. The sediments consist of landslidemass, rockfall,debris,karst collapse mass, etc. The thickness of the sediments determined by high resolution shallow seismic detection is 40m to 60m and can be divided into three wave velocity layers. A comprehensive conceptul model is set up and UDEC method is applied to simulated it. The formation and evolution process of the loose sediments can be divided into four stages geologic energy accumulation, fault system formation, rebound deformation and unload fracture, and epigenic reworking. Karstification is important to control the whole process.