Embankment dams, widely constructed and covering extensive areas, frequently experience material degradation due to seepage-induced weakening. Minor seepage can lead to progressive wetting deformation of support structures and subsequent failure of the impermeable elements. Major seepage triggers continuous seepage deformation and even catastrophic failure. Examples include the collapse of concrete face slabs and cushion erosion in Hunan’s Zhushuqiao and Baiyun dams, core wall defects in Sichuan’s Shiziping dam, and the collapse of Qinghai’s Gouhou concrete-face sand-gravel dam.

The in-situ anisotropy induced by the layered compaction of embankment dams and long-term sedimentation of overburden, as well as the in-situ stress caused by overlying loads, significantly influences the seepage-induced weakening effects on dam materials. Existing experimental apparatus inadequately replicate in-situ anisotropy, stress, and hydraulic gradients, necessitating advanced apparatuses to simulate in-situ seepage-induced weakening characteristics for the predictive evaluation of the embankment dam safety.

·   Development of an experimental apparatus for field sampling and laboratory sample preparation to reproduce in-situ anisotropy ;

·   Design of an experimental apparatus for simulating progressive seepage deformation under in-situ anisotropy;

·   Innovation of an experimental apparatus for simulating progressive wetting deformation under in-situ stress.

·   An apparatus for simulating the seepage deformation characteristics of overburden under in-situ stress has been developed, and a device for preparing anisotropic soil samples of coarse-grained overburden has  been invented. The combination of field-oriented and laboratory-oriented methods enabled the preservation of in-situ anisotropy and the determination of directional combinations.

·   An "Oreo"-style sleeve osmometer has been developed for sidewall installation on the flexible latex membranes. A soil-water separation technique for seepage deformation tests with controllable outlet hydraulic head has also been established. Furthermore, a triaxial seepage deformation testing system has been innovatively developed to realize the full-scale measurement of deformation, hydraulic gradients, and particle migration.

·   A progressive wetting process control device that simulates steam or drip effects under in-situ stress has been invented, a graded-load wide-range force sensor has been created, and a measurement device for progressive water absorption and wetting processes under in-situ hydraulic head has been developed.

The developed experimental apparatus has been successfully applied to critical projects, including the Lijiayan concrete-face rockfill dam, the Shuangjiangkou gravelly soil core rockfill dam, and a key hydropower project. It has provided robust support for engineering demonstration, process consulting, and real-time adaptive design, generating substantial social benefits. The apparatus demonstrates strong potential for widespread application.

Figure 1 Experimental Apparatus for Field Sampling and Laboratory Preparation to Reproduce In-situ Anisotropy

Figure 2 Experimental Apparatus for Simulating Progressive Seepage Deformation Under In-situ Anisotropy

Figure 3 Experimental Apparatus for Simulating Progressive Wetting Deformation Under In-situ Stress