Stability Research And Support Design For Surge Shaft Cavern Group Of Guangzhao Hydropower Station

Guangzhao hydropower station is the first and largest cascaded power plantin Beipanjiang River and constructed as the second batch of key projects of "Electricity delivery from the West to the East", undertaking the dutites ofadjusting power peak and frequency, and supplying load and emergency reserveafter the completion.Water diversion and power generation system on the right bank of theGuangzhao Hydropower Station adopts " two caverns and two shafts and foursets of turbine generator unit" arrangement. Surge shaft and the lower cavernsinclude the shaft body of surge shaft, connecting section of diversion tunnel,bifurcated pipe, upper horizontal section of pressure piping and1#forkedcavern for construction. Caverns intersect each other in the layout, having alarge size of structure, small thickness of the rock body between caverns(heightof surge shaft is106.5m, shaft excavation diameter is24.0m, minimumthickness between the shaft body is20.38m). Low part of the shaft body andbifurcated pipe section are affected by the cutting of1#construction forkedcavern and J1soft and weak interlayer, the place lower than EL690m have arather broken rock body and poor rock stability due to the erosion of theunderground water.During the study period, the Guangzhao hydropower station is stilloperating in the experimental stage. In this thesis, engineering geologicalconditions of surge shaft is simulated in accordance with the undergroundcaverns layout and excavation measures of construction and supporting designand other parameters etc., using ANSYS finite element program in the analysisof the rock stability for the surge shaft caverns in order to verify thepreliminary engineering design analysis methods used in the calculation andsupporting measures of construction is reasonable or not, include but is notlimited to the following:1) According to the cavern layout and excavation methods and supportingmeasures, the dimensional finite element analysis of the stability of surrounding rock for surge shaft shall be carried out in combination with the engineeringgeological conditions;2) Collecting monitoring data of the prototype of the surge shaft, throughthe analysis of its construction,supporting design and safety monitoring of keypositions shall be identified basing on the the operation of rock stressdeformation and development trends;3) The reasonability of preliminary computational analysis conclusionsand supporting measures of construction of surge shaft shall be evaluated;4) According to the monitoring data of the prototype, rock stability andoperational safety of the surge shaft shall be evaluated;5) Pursuant to the foregoing calculation results of the analysis, anoptimization of similar supporting measures of construction of undergroundengineering design shall be recommended.The surge shaft of the Guangzhao hydropower station belongs to thelarge-scaled type with the diameter larger than20m. By collecting, analyzingthe recent stress, deformation monitoring data of surge shaft cavern groups,surge shaft is proved in good condition since the operation so far, whichindicates that the stability analysis results and supporting measures ofconstruction of surge shaft cavern groups of Guangzhao hydropower station arereasonable for the reference by the design of similar underground engineeringprojects.