某水利枢纽坝区构造特征及其对岩溶发育规律的影响

某水利枢纽区构造基本格局形成于早白垩世的燕山运动,此时构造应力场以NE向为最大主应力方向,形成了规模较大的NE向百兴向斜;渐新世以来,区域表现为大面积的间歇性隆升,构造应力场转变以NW向为最大主应力方向,形成坝区占统治地位的NE向构造,在坚硬的岩层中形成大量节理裂隙,软弱岩层中则表现为塑性变形。这种构造特征对岩溶的发育具有控制性作用:(1)构造发育史控制了岩溶发育演化史,(2)构造运动的间歇性导致岩溶的多层性及继承性,(3)褶皱限制了岩溶呈NE向带状分布,(4)不同岩层内构造特征相异导致岩溶仅在某些岩层内较发育,(5)节理裂隙控制了岩溶发育的部位及形态规模。

TECTONIC FEATURES OF A HYDRO PROJECT DAM SITE AND THEIR INFLUENCES ON KARST DEVELOPMENT

The basal tectonic pattern in a hydro project dam site is due to the Yanshanian movement of Early Cretaceous, and direction of the major principal stress of the tectonic stress field is northeast in this period, which formed the large Baixing syncline. From Oligocene till now, the ground of this district has risen intermittently on a large-scale and the direction of the major principal stress of the tectonic stress field turns northwestwards, which resulted in dominant northeastward tectonics, and a great number of joints or cleavages came into being in those hard rocks, while only some plastic deformation but not joints occurred in those soft rocks. These tectonic features in this district have great influences on the karst development; (1) the history of tectonic development controls the history of karstification; (2) the intermittence of tectonic movement led to multi - stratification and succession of karst; (3) the northeast-axis folds made karst development in a northeast direction, too; (4) differences in tectonic deformation in different rock formations led to karst development in those hard jointed rocks; and (5) the joints control the location, scale and configuration of karst.