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                       Foundation Condition of Yazagyo Dam, Kalay Township, Sagaing Division by using Engineering Geotechnical Investigation and Elastmeter Test
                                                     Myo Thandar Win#1, Kyaw Htun*2, Khin Soe Moe#3
                                            #Department of Engineering Geology, West Yangon Technological University
                                                                        [email protected]
ABSTRACT
Engineering geological investigation of Yazagyo Multipurpose Dam Project was carried out in order to provide engineering geological information, especially for foundation of the dam, saddles and other appurtenant structures. The engineering geological interpretation along the dam axis reveals that the entire Chaung Section is composed of highly pervious slope washed deposits of which the thickness ranges between 20 to 88 feet at the right bank and 40 to 50 feet at the left bank. Lugeon values at the right bank (8 to 80 Lu) are more than that of the left bank (5 to 60 Lu), especially at the flanks of Talone Taung and Khamauk Taung where debris deposits occur. Beneath the gravel and debris deposits, indurated sandstones which are hard and dark brown in colour, and mudstone (from the Pane Chaung Group) are observed from the drill hole-data. These strata show steep dipping and trend NNE-SSW direction and the main dam alignment crosses the regional structural trends obliquely leading to unequal settlement of the dam and serious leakage of water not only through porous media but through bedding plane also. From the observation records in the right abutment, the entire section is composed of Yazagyo metamorphics, sheared serpentinites and dolerite rocks. Although the entire body of Khamauk Taung is made up of radiolarian chart, the confirmation drilled holes show that these drilled holes constitute weathered serpentines rocks below 10 to 40 feet depth. Again, according to the drilled hole, serpentinite rocks are observed at the upstream portion of the left abutment. The foundations of all saddles, penstock, power house and spillway are founded on weathered crushed and jointed Yazagyo metamorphic rocks, especially in upper portion. However, fresh serpentines rocks are observed near the penstock and power house. In this paper, engineering properties of serpentines and Pane Chaung Group, Yazagyo metamorphic rock and dolerites are discussed. The treatments of foundation, the excavation procedure and stability of right abutment are also described.
According to the bore-hole data and field observation, serpentinite rocks, with dolerite dyke are observed both in left and right abutment. Due to the mineral composition, the real value of RQD and compressive strength cannot be measured in usual way of measuring of other rocks. Therefore, the strength of these rocks are measured with some in-situ such as plate bearing test, and Elastmeter Test.
Keywords – Dolertie Dyke, Serpentinite, Green Schist, Landslide, RQD, Elastmeter Test