Abstract
Clay–gravel mixture has been widely used in high embankment dams and understanding its seepage characteristics is critical to dam safety. From the instrumental perspective, the realization of continuous pressurized water supply becomes a key technical challenge, significantly restricting the working conditions replicated in previous seepage apparatuses. To this end, a novel water provision system, relying on parallel-disposed sensor-based pressure devices, was introduced, so that the application of an existing large-scale stress-controlled apparatus can be expanded to long-term seepage tests regarding coarse-grained cohesive soils. Constant-head permeability tests were conducted on original-graded clay–gravel mixtures to investigate their hydraulic properties, incorporating the influence of stress relaxation. Test results show that with 35% gravel content, the clay–gravel mixture is suitable for dam construction as the core material. The stress relaxation holds a marginal effect on the hydraulic conductivity of soil. The functionality of this improved apparatus is verified, especially under long-term seepage conditions.
Highlights
Seepage phenomenon, which is regarded as water flowing within continuous void spaces from a point of high energy to a point of low energy, can be found ubiquitously in embankment dams and other water-retaining structures [1,2,3]
Since the renovated water provision system proposed in this study offers the pressurized water through the same pipe, it can be transplanted into the existing apparatus without structural modification
A similar relationship between the velocity and the hydraulic gradient is recorded in Re-2, revealing that Darcy’s law remains applicable when the original-graded soil specimen is subjected to seepage flow, irrespective of the addition of gravel particles (35%)
Summary
Seepage phenomenon, which is regarded as water flowing within continuous void spaces from a point of high energy to a point of low energy, can be found ubiquitously in embankment dams and other water-retaining structures [1,2,3]. The relevant seepage control is of vital importance, given the high proportion of seepage-related dam breach accidents [4]. This issue has become increasingly severe, since the projected dam height in. Among various factors associated with uprising dam height, the hydraulic factor plays an essential role in triggering the seepage erosion [6,7]. Apparatuses that can be used to assess the hydraulic stability have been tremendously fostered, and some take into account the influence of stress states [8,9,10,11]. A few apparatuses tailored for large specimens are technically constrained from realizing the high hydraulic gradient, mainly because of the difficulty of producing highly stable hydraulic pressure
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