دانلود رایگان مقاله انگلیسی نفوذ پذیری برای بازسازی هسته های سد - نشریه الزویر

ABSTRACT

Grouting methods are known to effectively remediate the dam foundation or the abutment. However, remediation grouting of the deteriorated embankment earth-core itself has rarely been performed or studied. In this study, low-pressure permeation grouting is adopted to remediate the deteriorated central core layers of five aging dams. Technical features of each dam's deterioration are described, such as sinkholes, slope failures, fluidized clay cores, and wet zones on the downstream surface induced by excessive seepage. This study suggests several empirical standards for the application of permeation grouting to the improvement of core permeability, including grout mix, injection period per stage, injection rate, and maximum fluid pressure to prevent hydraulic fracturing. The results of this empirical case study can be applied to effectively remediate degraded dam embankment cores to decrease their permeability and minimize the risk of hydraulic fracturing, without requiring a reduction in the reservoir water level.

5. Conclusions

This paper analyzed and discussed remedial grouting techniques applied over ten years to five existing deteriorated dam clay core layers. For remediation grouting of dam embankment cores, a totally different design concept is required compared to typical pressurized grouting applications, such as dam foundation or coffer dam grouting. Remediation grouting without reservoir water drawdown is known to be e ffective; however, case history reports on this topic are rare, and no empirical standards for applying the method have been presented. In this paper, low-pressure remediation grouting techniques were applied to five existing cored dam embankments that showed either exterior or interior de ficiencies in core impermeability. The dams exhibited embankment deterioration of the following types: randomly distributed fluidized cores of high water content, wet downstream surfaces, sinkholes on the crest, downstream slope failure, or granular cores in the areas adjacent to the dam crest. Various validation methods demonstrated that site-speci fic lowpressure permeation grouting can effectively remediate dams by improving the impermeability of deteriorated core layers. Fundamental empirically proven technical speci fications are proposed, including limits on the grout pressure, grout flow rate, injection duration, initial grout mix ratio, additive ratio, and grouting condition change. Signature characteristics of the most commonly e ffective remedial permeation grouting techniques include the following.