Systematic Researches On Red Bed Rock Mass Engineering Geological Problems Of Water Resources And Hydropower Projects In Sichuan Basin, China

Red bed rock distributes all around the world, and in China, most of it distributesin Northwest, Southwest and South of China, especially, it distributes widely,continuously and typically in Sichuan Basin, with dense population and advancedinfrastructure of industry and agriculture being there. However, total amount of waterresources in Sichuan Basin is poor, runoff-time pattern is not uniform, draught andflood happen very often, these have resticted the development of industry andagriculture. As for the water energy, it is less than West Mountain Area of SichuanProvince, but Sichuan basin area is closer to the demanded centre and with easytransportation condition, so the development condition of hydro power is better.Hence, there is much experience about water resources and hydro-electricity projectsin Sichuan Basin, which have built up a large amount of successful engineeringexamples and experience, meanwhile, there are some kinds of engineering geologicalproblems exist, such as, dam foundation rock sliding beneath the dam of HelongtanReservior Project; gypsum erosion of in dam foundation rock of GaofengshanHydro-power Project; rock-swelling in Huilonggon Tunnel,etc..At present, just half of water energy projects had been completed whilebuilt-ratio of irrigation area is only about11.5%in Red-bed rock area of the Basin, sothe water resources and hydro power construction in Sichuan red bed basin area has alarger development foreground in the future.Therefore, as for achievements or results of systematic and profound summary,analysis and researches on red bed rock property and its engineering geologicalproblems, there is much more project experience and lessons about the researchfoundation, wide real demand for the project practice, large and wide appliedforeground. According to the above, based on almost100large or medium water resourcesand hydro-power projects in Sichuan basin red bed rock area, the author with morethan20years work experience, refering to relative data in or out of China, carried outsystematical researches on major engineering geological problems in Sichuan Basinred bed rock mass, to provide theoretical and methological supporting for protectingand developing water resources&hydropower appropriately and effectively.Based on researches of red bed rock formation–transformation characters inSichuan Basin, the distributed rule of red bed rock lithologic characters, lithfacies andlitho-stratigraphic combination character is summarized in the dissertation, and thenthe physico-mechanical parameters come out through the analysis onphysico-mechanical test data of red bed rock in Sichuan Basin. Also, analysis anddiscussion on structure character about rock deposit formation of red bed rock massand it’s tectonically and epigenic transformation was finished, then, engineeringgeological zoning is going on. According to these above, researches on red bed rockstability and leakage problems in dam foundation have been carried out. At last,researches on some other particular geological problems in water resources andhydro-power project related to red bed rock mass such as pseudo-karst and swelling isdiscussed in the dissertation. Some major results of the dissertations are:（1）Based on almost100water resources and hydro-power project in SichuanBasin, the physico-mechanical and characters of red bed rock mass and some relatedgeological problems are systematically summarized; basic models of deformation andanti-sliding of dam foundation, as well as leakage of red bed dam rock mass with theirassessment methods are put forward, which provide basic thought-ways and methodsfor systematical analysis and evaluation on red bed rock mass engineeringgeological problems in water resources and hydro-power project.（2）Based he researches on the evolvement sedimentary facies, distributing andlitho-stratigraphic combination characters of red bed rock from Jurassic to Tertiarythroughout Sichuan basin, the thesis found the formation characters of the red bed inSichuan basin.（3）Based on the classifying, statistics and analyzing on test results nearly800sets of red bed rock in Sichuan basin,the thesis found that red bed rock is generally ofsoft rock,that is to say, the sand rock belongs to relative-soft rock（Rb=15～30Mpa）,pelitic rock in red bed rock area all belongs to soft rock（Rb=5～15MPa）or very-softrock（Rb≤5Mpa）. Generally speakihg, red bed rock is of soft rock, and the red bedrock mass is of hard layers and soft layere alternately in structure,the soft intercalationof the red bed rock mass usually exists between sand rock and pelitic rock or withinpelitic rock, and it spreads along the stratification plane of the rock. Authough red bedrok is generally belongs to soft rock, some sand rock is of mediumhard（Rb=30⁶0MPa） to hard rock（≥60MPa）,some pelitic rock is is of relative soft rock（Rb=15～30Mpa）to medium hard（Rb=30⁶0MPa）;these kind of red bedrelatively harder mainly exists northweast of Sichuan basin; the spacial distributingcharacters about the strenth of red bed rock throughout the Sichuan basin hassomething to do with the sedimentary environment.（4）According to the major factor of red bed rock formation and tectonictransformation, taking account of the topographic and hydrogeological condition etc.,the red bed rock mass in Sichuan basin is divided into3geological zones, that is:Northwest Basin zone （I）, Center Basin zone（II）, East Basin zone（III）; furtherlyNorthwest Basin zone （I） is divided into2secondary sector, Secondary East Basinsector（Ⅰ-1）and Secondary North Basin sector（Ⅰ-2）, also, the main geologicalproblems in the each zone has been analyzed and evaluated.（5）Based on the red bed rock mass structure characters,9classes of damfoundation deformation and9kind of model about anti-sliding stability of damfoundation is put foreword. The main geological elementary factor about each damfoundation deformation and anti-sliding stability are summarized, and the evaluationpoints to the corresponding problems is also put foreword in the dissertation.（6）Through the analysis on geological forming process of permeable zone in redbed rock mass, based on statistic and analyzing nearly4000sets of water-pressuretests data, the viewpoint that the formation of the permeability of red bed rock mass ismainly controlled by epigenic transformation such as weathering and unloading action.By numerical modeling and analyzing, basic rules of percolation through damfoundation and abutment,as well as the mainly designing points of anti-percolation inred bed rock area is gotten, that is to say, the objects of the anti percolation is thepermeable weatering rock mass, it is enough and safe for the projects.that the antipercolation curtain is just need going through weathered zone and gets into fresh rockwith suitable depth or length.（7）Based on the analyzing of Tongtou Project, the dissertation found that theintensity of pseudo-karst of conglomerate is lower than that of limestone, which iscontrolled or dominated by the difference of soluble components（CaO/MgO）ofthem. According to the analyzing on the erosion of red bed with gypsum K＝(ABS(V_{ppseduo-karst}-V_pfresh)／V_pfresh)×100ï¼…,as an intensity evaluation factor ofpseudo-karst action is bring forward. Through the regression relationship analyzingbetween Vpand rock mass engineering mechanical index, a method for quantitativeevaluating the pseudo-karst weakening effect concerning rock mechanical index byrock mass sound wave value Vpis also put foreward in the dissertation.（8）Based on the typical project example about swelling of surrounding rockleads to liner brokening in Huilonggong Tunnel, according to the qualitative analysisand quantitative modeling of the deformation and failure mechanics, main points for constructing and designing in swelling rock tunnel is put forward.