مقاله انگلیسی رایگان در مورد آنالیز اثر تاخیر نشت سد خاکی بر اساس اطلاعات – الزویر 2018

Following the impoundment of an embankment dam, the seepage field of the dam body is seen to gradually stabilize. At this point, seepage within the dam body is primarily influenced by environmental variables, such as the upstream level, which demonstrate a certain lag effect. As one of the main problems encountered in data analysis of embankment dam monitoring, lag-effect analysis of dam-body seepage plays an important and central role in health diagnosis and safety monitoring of embankment dams. For example, the lag time recorded at each measurement point must be known when using monitoring data to determine the saturation line, thereby determining the relationship between seepage pressure and upstream level. Lag-effect analysis is also required in selecting preset factors when establishing seepage models. The causes and mechanism of the seepage lag effect of embankment dams are complicated. Gu et al. (2005) summarized the mechanism as follows. Variations in the upstream level alter the dam seepage field from one stable condition to another, and the transition process occurs over a certain time period. This transition is the main cause of the seepage lag effect. Delayed transmission of water pressure in the dam body is another factor contributing to the lag effect. Further, response times of seepage monitoring sensors, such as piezometric tubes and osmometers, with regards to variations occurring in the seepage state could also contribute to the lag effect. At present, only a few specialized studies are being conducted with focus on the seepage lag effect in embankment dams. The basic method used in these studies involves comparison of the process line of the measured water pressure with those of the corresponding upstream water level. This technique serves to qualitatively determine the lag time of the seepage in terms of the appearance time of “peaks” and “valleys” in the process line. Gu et al. (2005) utilized the mean value of the upstream water level over several time periods as the precession factor for the hydraulic-pressure component in their seepage monitoring statistic model, thereby considering the hysteresis effect of seepage. In addition, several scholars have investigated seepage characteristics of embankment dams while also inadvertently studying aging characteristics of seepage. Ozer and Bromwell (2012) used the finite element method and measured seepage data to simulate seepage and aging characteristics of embankment dams. Simeoni (2012) investigated the relationship between the lag time and pore-water pressure using the piezometer experimental method. Wang et al. (2013) studied the influence of the crack self-healing phenomenon on the permeability of dams via 12 simulation tests. Lee et al. (2007) explored the tracer experiment method combined with specific engineering to study the concentrated seepage path of embankment dams. However, a common drawback of the studies mentioned above concerning determination of the seepage lag time is the exclusive utilization of qualitative estimations without quantitative measurements. It is, therefore, necessary to apply new ideas and methods to accurately quantify the seepage lag effect.