Nuozhadu Hydropower impervious core wall engineeri -

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Nuozhadu Hydropower impervious core wall engineering geological characteristics of soil materials

Optimal water content (15.6%) high 4.0%, close to the plastic limit water content (18.9%), suitable for direct on the dam, construction of better conditions; maximum dry density than the natural dry 1.779g/cm 14% high density, compaction better performance; permeability coefficient of 2.10 ~ 10cm / s,[link widoczny dla zalogowanych], seepage is good; in the 0.1 ~ 0.2MPa pressure, the compression coefficient of saturated water immersion 0.16MPa ~, with the compression performance; soluble salts and organic matter content is low; a non-dispersive clay and non-expansive soil (free expansion of 16.4%). Control SDJ17-78 \3 gravel wall material Nouzhadu dam 26l, 5m, so impervious material in addition to meet the performance requirements of seepage, but also must have good mechanical properties, in order to work with the deformation of rockfill dam coordination shell, reduce the dam shell of the core wall of the arch effect and improve the cardiac wall stress and strain, reduce the probability of occurrence of cracks in the core wall. Domestic and foreign soil from the construction of impermeable dam dam body experience, body is made of high embankment dam seepage moraine soil, weathered rock and gravel soils represented a wide size distribution of soil material is increasingly common,[link widoczny dla zalogowanych], the use of gravel soil as high rockfill dam impervious advantages are: higher density obtained after compaction, so impervious with high strength and low compression; cracking in the impervious limit the conduct of cracks, and to Crack downs poor increased, decreased flow of hydraulic gradient along the crack, while for II,[link widoczny dla zalogowanych],. ◆. ◆ _. - Easy to sew wall erosion of coarse particles on the percolation limit erosion along the cracks have a positive role in the filter under the protection of the self-healing effect of crack is also good; used to facilitate construction of gravelly soil, can be used to transport heavy machinery and grind pressure, moisture content is not sensitive to rain-fed areas than the clay construction materials easier. Soil material used in the early stages of planning, the two types of earth materials: mixture, the thickness of the material field can be taken within the mixed soil; ② residual soil, in addition to pushing the surface slope of about 2m thick layers of soil material plot. According to test results, both material with grain size, compaction density difference between the physical and mechanical indicators are small, a medium compressed soil, the dam settlement calculation, final settlement is relatively large volume in excess of regulatory requirements. On the other hand, with the international than other high-core dam, Nuozhadu farm yard of soil particles of soil material is noticeably thin, so were of gravel mixed with soil material. In l470kJ / m compaction features, the 35% of the gravel yard of soil material and soil test results is shown in table mixed l. As can be seen from Table l, compared with mixed gravel materials maximum dry density 0.15g/cm, greater than 5mm in diameter compaction of soil material content of 33.85%, gravel and anti-material deformation index mixture shear strength parameters were greatly improved, with layered summation method for the completion and final settlement of the heart wall, mixing ratio of gravel material is 20%, while the permeability coefficient of soil material has not been gravel content increases soil material essential changes occur,[link widoczny dla zalogowanych], and gravel soil behind the physical and mechanical material parameters were significantly better than the mixed soil material. In summary, the experience from the construction and test results of soil material point of view, the heart wall Nuozhadu high dam, the soil should be used as a gravel impervious material. Gravel soil Nuozhadu access works can be taken two ways: First, through the exploitation of the lower layer of strongly weathered soil material mixed with the upper stone; Second, artificial stone mixed with people. According to exploration results, soil slope deposits yard thick 0.6-2.5m, constructed residual thickness 3.5 ~ 21.6m, generally following the 9 ~ 14m weathered rock. To the lower part of the strongly weathered through the exploitation of stone and the upper layer of soil material to obtain gravel mixed soil, due to slope, uneven residual layer of mixed gravel mining is difficult to guarantee the quality of soil, and may experience lower exploitation of groundwater is not conducive to excavation; In addition, the soil material is mainly purple shale rock, soft rock, compressive strength is low, softening coefficient, even after the weathered part of rock, after rolling in the heavy compaction machinery, gravel volume will not increase too much. So. Safety from the engineering point of view, in order to effectively increase the core material of the gravel content,[link widoczny dla zalogowanych], the use of fresh games to add stone or artificial granite aggregate breccia way to obtain more appropriate gravel soil impervious material.

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