Preliminary Analysis Of Greenschist At The Right Abutment Of Jinping I^st Hydropower

The dam area of Jinping Ist Hydropower has narrow valleys, steep valley slopes;the relative altitude of the slopes is up to 1000-1700m, the range of slope is 30-90°, this area ismainly constituted by the third paragraph metamorphic sandstone of triassic zagunao,board rock(T2-3z3), the second paragraph marble schist folder (T2-3z2) and so on; thephase formation is large, geological structure is complicated, and the stress levels are high. Theright bank of the dam site is along the slope, and constituted of green marble schist; Generally,the stability of the slopes is better, but still has some local stability issues andgeological defects.According to the amount of chlorite, mica and quartz, greenschist can be divided intocalcite chlorite schist and quartz chlorite, the wet compressive strength of these two freshrock are 25~50Mpa and 40~60Mpa, which are lower than other bedrocks. Calcitechlorite schist, especially as the negative factors of right abutment's stability, because of itscharacteristic of schistosity development, rich in chlorite, soft, loose and easy witha smooth sense of weathering. it makes an important sense to evaluate the developmentalcharacteristics of greenschist correctly, in order to assess the stability and reliability of theabutment. Therefore, under the guidance of my supervisor, combine with the practice ofscientific research in Jinping Ist Hydropower Project, author carried out thesis researchwork with the master's thesis"Connectivity Features and Stability Against Sliding'sPreliminary Analysis of Greenschist at The Right Abutment of Jinping Ist Hydropower", inorder to obtain useful results for this project and instructive study ways or means for similarprojects.In this paper, the geological conditions of the dam were introduced comprehensively andsystematically, such as the topography, lithology, geological structure, weatheringand unloading, groundwater; based on understanding the specific geological environment ofgreenschist, this paper described the development features and proposed the connectivityrate value of the greenschist on the right bank of Jinping Ist Hydropower, finally the stabilityagainst sliding on the right abutment has been evaluated. The specific research contents andresults are as follows: (1) The research of engineering geological characteristics about the greenschist onright abutment: based on the catalog informations of greenschists which are at afeasibilitystudy adit, right bank of the dam foundation (including the downstream slope) , undergroundpowerhouse of right bank and the slope of power inlet; as well as based on rebound andacoustic testing data; using mapping (flat cut chart, profile) and statistical methods; madestatistics about the development of greenschist layers, shape and size, composition andstructure, weathering characteristics, mechanical properties and so on; also analyzed thebasic engineering geological characteristics of greenschist on the right abutment.(2) The research on connectivity rate of the greenschist at right abutment: looking thegreenschist as fracture structureas surface, and used the following three methods to research theconnectivity rate of greenschist: first, based on the whole trace length greenschist's dateswhich feasibility track adit, dam foundation and excavation slope revealed, analyzed theprobability (frequency) distribution of greenschist's length and spacing, calculated connectivityrate of the greenschist at right bank's main horizons using full trace length'sbandwidth projection method; Second, using trace length estimation method of theuncertainty model, determine the connectivity rate of the greenschist which feasibilitystudy adit, irrigation and drainage tunnel as well as the right bank plant revealed; Third, basedon the measured frequency distribution of greenschist's pitch, length, orientation andmeasured angle, using Monte Carlo method which is used in fracture network simulation,simulated the spatial distribution of right abutment's greenschist; and then calculatedconnectivity rate of the greenschist at layers using bandwidth projection method. Basedon these studies, given the recommended value of the connectivity rate on main layersright abutment.(3) The analysis of right abutment stability against sliding: First, according to thedevelopment features of the greenschist at right abutment's faults and fissures, analyzed theboundary conditions of right abutment's stability against sliding,identified adverse combinations; according to the research results about the mechanicalparameters of dam rock mass and structure surface rock, determined the comprehensiveparameter of boundaries; then, with the rigid body limit equilibrium method, calculated andanalyzed right abutment stability against sliding under various conditions, evaluated thestability against sliding of right abutmention.