Experimental Study Of Clogging Effect On Permeability Of Dam Foundation Soil For Plateau Reservoir

Since the 1990s, China's Tibet region have built a large number of water conservancy facilities in order to speed up local economic and social development. At present, the dam foundation of anti-seepage mainly deals with anti-seepage wall and curtain grouting, under the conditions of the river loose accumulation of medium in the mountains. But the effect of impermeable reservoir foundation is often unsatisfactory, especially in the mountains-gully rivers, deep rough coarse gruanular soil and over coarse-grained soils coverage will be doubled to increase the difficulty and cost of anti-seepage.Therefore, looking for a cost-effective method of reservoir anti-seepage becomes extremely urgent,according to the special geological conditions in the Mountain plateau.This paper presents a sieve deposit lobe of"clogging effect",by tracking survey with Qiongjie reservoir which is operating in Shannan region of Tibet,that is, water storage and seepage flow have an effect,as the time,the sieve deposit lobe(rock and soil of the dam foundation) has a clogging of internal role, making the foundation of rock and soil permeability reduction of leakage reduction. Based on this, the study area of this paper is the south of Brahmaputra River in Shannan region of Tibet to Kong-Shan Rail Rafah ,the region has been proposed Zhuoyu reservoir and the reservoir built Jiangxiong represented on the mountain plateau alluvial soil formation conditions of deposition Plugging effect on the indoor simulation experiments.Designed and produced clogging infiltration instrument, and summed up the clogging test steps and attention to the matter in the testing process through exploration. Clogging infiltration instrument is based on the characteristics of coarse gruanular soil and produced by the head principle, the structure is similar to seepage deformation tests,but the difference is that water supply systems is carried out from top to bottom. In the tests,to add Particles of different grains to the instrument,and observe the continuous changes of pore water pressure on the different depth through the left side of the apparatus, which reflect changes of sample permeability in the process of clogging test.In clogging tests, the soil samples are all taken from Zhuoyu proposed reservoir in the regions of Tibet Shannan. Clogging infiltration instrument is filled with grits and screes of Quaterna Holocene alluvial-proluvial,because some soil particles have gone beyond the scope of the instrument to allow, so based on earthwork experiment regulations,a method of mixed soil samples is taken to deal with over-size particles,that basic guarantee for the design grade,Structure and pore situation of the sample similar to the original grade. Clogging test adding soil sample are taken from the Zhuoyu reservoir on the dam area Zhuoyu ditch upstream edge Zuoyouan alluvial fan floodplain and the upper reaches of the river, upstream to the reservoir simulation clastic material source.In this paper,make a series of indoor simulation clogging permeability test with the grits and screes taken from Zhuoyu proposed reservoir in the regions of Tibet Shannan; establish the clogging test model,and preliminarily discuss the clogging of creation, development,process of action and influencing factors;summarized some related concepts of clogging,and proposed the two concepts of "optimal size range","characteristics pore"in clogging area the first time;based on test dates, briefly analyse the mforation conditions and effecting processes of clogging from the particle samples of the pore structure and stress; initially overlook that the clogging of the reservoir as a new method has been applied to engineering practice impermeable prospects, pointing out that the current clogging pilot study of the shortcomings and clogging in-depth study of the role general direction.Through this study,the following conclusions are made: 1. Based on this test grade soil samples, clogging effect is an objective existence, clogging test soil samples on the role played by the reduced infiltration effect is more obvious.2. From clogging test data, the overall sample flow rate, permeability coefficient increased with the passage of time decreases, but the test system head loss is concentrated in the soil samples of a soil layer, but not all, it is precisely Because of this led to the reduction of soil permeability of the sample of the overall decline in infiltration capability.3. Other areas of silt from the definition of preliminary summary of the effect of clogging the relevant concepts and types.4. Proposed the two concepts of "optimal size range","characteristics pore"in clogging area the first time. Based on this test grade soil samples, under the condition of 2.2 m in the head, the optimal size range is 0.5 to 2 mm; under the condition of 2.7 m in the head, the optimal size range is 2 to 3 mm. Hydrodynamic conditions improved to the clogging effect of changes in the optimal size range. The characteristics pore of Test soil samples is 0.5 to 1 mm tablets identified by the group.5. Add further improve the penetration of the concept of deformation. Infiltration deformation not entirely equivalent to the infiltration and sabotage, infiltration of deformation may lead to the development of the two results, one is the infiltration and sabotage, a role that is clogging.6. Artificial clogging the reservoir as a new foundation impervious ideas, with a smaller, cost-effective application of the characteristics of the prospects for engineering practice is still very substantial.