| Altered rock(band) is a main geological defects of hydropower project dam foundation rock mass, often constitute the main engineering geological problems of large scale hydropower project. The Dagangshan Hydropower Station dam foundation rock geological background is complex, rock alteration type is also complicated, strong alteration have a significant impact on the stability of arch dam foundation rock mass, become the main engineering geological problems of dam foundation rock mass. The author in the hydropower station dam foundation rock mass as the object of study, in the background of rock alteration on the basis of the analysis of rock mass, using the method of macro and micro alteration characteristics and its alteration mechanism, and the rock mechanics methods of the alteration effects on physical and mechanical properties of rock body, in order to evaluate the quality of altered rock mass and its utilization. Get the following main results.(1) In the analysis of rock alteration and erosion background becomes the basis of characteristics of the system research, division of dam foundation of granite rock mass of the dam foundation of granite alteration type, alteration type is divided into hydrothermal alteration(including K-feldspar alteration and sericite- chlorite alteration), tectonic alteration(quartz epidote Petrochemical alteration) and weathered alteration(weathered altered rock, weathered rock, weakly weathered altered rock,weak weathered rock alteration and micro). According to the micro petrological characteristics of macro characteristics of altered space output, analysis and study of the formation mechanism of various types of altered rocks, the system changes the petrologic characteristics of different types of alteration and the alteration of the granite.(2) Divided the diabase alteration degree, divided into massive diabase, diabase and diabase fragmentation- foliated diabase and argillic alteration rock.The study on variation rules of different degree of alteration of diabase rock mass structure characteristics and micro petrological and mineralogical characteristics, show that the tectonic dynamic alteration of the diabase had strong chloritization, and sericite and illite formation, enhance the alteration mineral content along with the alteration degree,the tectonic schist and argillaceous rock alteration mineral content up to 59% and 76%. According to the qualitative judgment and indoor particle analysis test system divide the engineering geological type with dikes and mud groups,SN and NE to the dike for structure of B2 and B3, NW-NWW and EW dikes were B1 rock debris type structure, argillic alteration belongs to B4 clay structure type.(3) The tectonic erosion diabase variable mechanism, according to the rule of change, the micro petrological and mineralogical characteristics of altered diabase space changes and the dynamic conditions of tectonic erosion diabase variable mechanism and argillic zone formation mechanism. It is considered that the tectonic dynamic alteration mechanism for dynamic fragmentation and dynamic metamorphism, the main reason is rich in pyroxene dark minerals and hydrothermal metasomatic, multistage structural slippage and groundwater constitute dikes altered clay.(4) In the altered rock microscopic characteristics and mechanism on the basis of the analysis, combined with the indoor physical and mechanical tests, the system of the alteration of the physical and mechanical characteristics of rock mass in dam area, the physical water of various types of altered physical properties, strength properties and deformation characteristics. Altered rock are mainly controlled by structure and mineral composition, alteration type and degree of alteration effects mainly as follows: the hydrothermal alteration sericite chlorite with Kfeldspar alteration mineral content is high and weak., density and rebound strength, saturated uniaxial compressive strength and deformation modulus are relatively low; quartz epidote petrochemical physical and hydrological characteristics and strength decreased a little, but because of epidote and quartz concentration causes the shear strength decreased significantly. Weathering altered granite and tectonic altered diabase showed the same regular pattern:With the increase degree of alteration, bulk density 、 particle density of weathering altered granite and tectonic altered diabase block gradually decreased, the opposite site its water content, water absorption, porosity and void ratio increased, also the strength and deformation modulus properties decreased.(5) The rigid bearing plate compression creep test were conducted with the disintegration of diabase and soft rock, the creep characteristics of altered diabase, establishes the creep constitutive model, and from the micropetrological characteristics and structure analysis, analysis of the impact of alteration on the creep characteristics of the Shi Bianhui ophiolite. Indicates that the tectonic alteration degree of soft rock large with respect to adisintegration of diabase, the deformation value is larger, long-term compression creep strength, low modulus of deformation characteristics of instantaneous modulus and creep.(6) On the basis of the above study and analysis of the influence on the rock mass alteration rock mass quality, established the altered rock analysis system, a brief evaluation of the altered rock availability. |
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