金沙江白鹤滩水电站旱谷地料场灰岩工程性状弱化成因

二叠系下统栖霞+茅口组灰岩通常风化程度低、强度高,但白鹤滩水电站旱谷地料场灰岩却出现工程性状弱化现象。为揭示白鹤滩水电站旱谷地料场灰岩工程性状弱化特征及成因,通过对料场及周边地质环境调查,结合钻探、声波测试、室内试验等手段可得:旱谷地料场灰岩弱化后强度仅为新鲜岩体强度的1/2～1/4;料场区弱化岩体可分为强风化带、弱风化带上段、裂隙构造带、溶蚀带;分别分布在泥质含量较高的灰岩透镜体和灰白色灰岩夹泥质微晶灰岩条带、地表P_1q+m-①层、裂隙构造密集带、岩溶溶蚀带;料场灰岩弱化是受灰岩物质成分、构造挤压、岩溶溶蚀作用和风化耦合作用而成。

Weakening causes of Limestone Engineering characteristics in Hangoudi Quarry of Baihetan Hydropower Station on Jinsha River

Limestone of Qixia+Maokou Formation of Lower Permian is usually with low weathering and high strength, while the limestone in Hangoudi quarry of Baihetan Hydropower Station appeared weakened engineering shape. In order to reveal its weakening characteristics and causes, detail field investigations, drilling, acoustic testing and laboratory tests are adopted. The results show: (1) the strength of limestone in Hangudi site after weakening is only one half to one quarter of the strength of fresh rock mass; (2) the weakened rock mass in material field area can be divided into strong weathering zone and weak zone. The middle section of the chemical zone, the fracture structural zone and the dissolution zone are separately distributed in the limestone sac with high argillaceous content and the limestone with argillaceous microcrystalline limestone strip, the P1q+m-1 layer on the surface, the concentrated position of the fracture structure and the karst dissolution zone (3) The weakening of the limestone in the material field is caused by the composition of the limestone, tectonic compression, karst dissolution and weathering.