| Deep geological disposal of high-level radioactive waste is currently consideredas the most technically feasible method for the final safe isolation of high-levelradioactive waste from human environment. That is necessary to select a naturalgeological barrier and set multiple engineered barriers (multi-barrier system) in theunderground repository in order to achieve long-term or permanent isolation of HLWfrom human environment. In the site selection process of HLW waste disposalrepository, many factors should be considered which included natural andgeographical condition, hydro-geological condition, rock properties and so all, amongthem the crust stability is one of the key factors in the repository siting. In this paper,we choose Xingchang and Jijicao selection as a main research area, the faults whichdisgovered in the Xingchang and Jijicao selection and in their vicinity are consideredas the main study object. In order to evaluate the crust stability of Xingchang angJijicao selection, we use the geomorphology survey, trench excavation, AMS14Cdating, OSL dating (OSL), electron spin resonance (ESR) dating and other methods,to identify the activity age of those faults, and the main results obtained are asfollows:1. Beishan area is preselected place for high-level radioactive waste disposalrepository in the Alax stable Block. There are20faults in and near the Xingchangselection, which can divide into5groups:(1) Xian Shuijing faults system, which isnorth-west strike faults and in the northwest of the Xingchang selection. Those faultsare distributed in the valley or groove that between the granite hills, and their finalactivity age is early-middle Pleistocene or Pre-Quaternary;(2) Jin Miaogou fault (F6),which was west-east strike fault and in the north of the Xingchang selection. Thisfault is left-lateral strike-slip fault and its final activity age is Pre-Quaternary;(3)Jiujing faults system (F20), which are north-east strike fault and located in the west ofThe Xingchang selection. Those faults belong to the normal and left-lateral strike-slipfault. The Jiujing faults group is in the proximity of the Xingchang selection and itsfinal activity age is late Pleistocene, but it is limited by its scale and something else, the influence of these faults on Xingchang selection is weak;(4) The faults system islocated in the Xingchang rock mass is north-east or North north-east strike faults.Those faults are discovered in the valley or groove that formed between the granitehills, and their final activity age is Pre-Quaternary;(5) The F95fault, which occused inthe south of the Xingchang selection. This fault is left-lateral strike-slip fault and itsfinal activity age is early-middle Pleistocene.2. There are12faults in and near the Jijicao selection, which can divide into2groups:(1) Hong Qishan fault (F1), which is est-east strike fault and appears in thesouth of the Jijicao selection. This fault is in the left-lateral ductile shear zone and itsfinal activity age is Pre-Quaternary; the faults system is located in the Jijicao Rockmass is north-east strike faults. Those faults ars left-lateral strike-slip fault and theirfinal activity age is early-middle Pleistocene.3、The Sanweishan fault, which belongs to the Altyn Tagh fault, is one of thebranch faults in the north-east of Altyn Tagh Fault. The distribution of this fault is inthe form of a series of linear fault triangle that is north-east strike. The lest-lateralvelocity of the fault is between0.1and0.4mm/a. Three trenching has reveled3paleoseismic events that place took in56ka,40ka and between7.4and2.4ka beforepresent, which means the Sanweishan fault was a Holocene activity fault.4. The Jiujing faults group is in the form of complex extensional horsetailsplay structure in geometry. The distribution of this fault group is in the form of aseries of linear fault triangle. This faults group is normal and left-lateral strike. Thehorizontal displacement is1.3～6.5m, and most of them is between3.0to4.0m, andVertical displacement is around3m. The trenching has reveled2paleoseismic eventsthat was occurred in76～78ka and22ka, which means the Jiujing faults groupbelongs to the late Pleistocene activity fault5. Refer to relevant secifications, we give the reginal custsal stability preliminarystandard that for the geological dispoal of high-level radioactive waste repository, andaccording to this regulations, we initial consider that the Xingchang and Jijicaoselection is in the crust stable area. |
PDF Full Text Request