Experimental and numerical modeling of diaphragm grouting in earth dams considering construction defects

• Published in: Modeling earth systems and environment Vol. 10; no. 2; pp. 2159 - 2185
• Main Authors: Fawzy, Momen A., Hassan, Nagy A., Saad, Neveen Y., El-Molla, Doaa A.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.04.2024; Springer Nature B.V
• Subjects: Chemistry and Earth Sciences; Computer Science; Concrete; Construction; Dam construction; Dam safety; Dam stability; Dams; Defects; Diaphragms; Discharge; Downstream; Earth; Earth and Environmental Science; Earth dams; Earth Sciences; Earth System Sciences; Ecosystems; Environment; Finite element method; Grouting; Height; Hydraulic gradient; Hydrostatic pressure; Math. Appl. in Environmental Science; Mathematical Applications in the Physical Sciences; Mathematical models; Numerical models; Original Article; Permeability; Physics; Pore pressure; Pore water; Pore water pressure; Seepage; Slope stability; Stability analysis; Statistics for Engineering; Velocity; Water pressure; Numerical modeling; Grouted diaphragm defects; Seepage control; Rehabilitation; Earth dam; Experimental modeling
• ISSN: 2363-6203; 2363-6211
• DOI: 10.1007/s40808-023-01892-2

Grouting is a common technique to rehabilitate old dams that started to leak. Nevertheless, grouted diaphragms are subject to construction defects which cause further seepage issues. In this study, a permeability tank experimental model and a finite element numerical model are used to simulate seepage through earth dams. The effect of using a grouted diaphragm on the dam’s seepage and stability is evaluated. The paper also investigates the negative effects of diaphragm construction defects, namely, thickness deficiency, cracking, and high permeability of concrete. Different scenarios are modeled for the grouted diaphragm without and with defects. Additionally, a toe drain is added in some scenarios to investigate if it enhances the stability of the dam. The seepage discharge, velocity, hydraulic gradient, pore water pressure, and downstream slope stability are evaluated. The grouted diaphragm reduced the seepage discharge by 20% in the case of partial grouting and up to 100% for full-height grouting, enhancing the stability of the dam. Yet, partial grouting increased the velocity at the diaphragm’s free end by 2–3 times its value in a homogeneous dam. Cracking of the diaphragm’s lower end was the most detrimental to the dam’s safety, while the high hydraulic conductivity of concrete came in second place. Using a toe drain increased the seepage discharge by 12–20%, but greatly lowered the pore water pressure, and enhanced the downstream slope stability by 20–23%. Hence, adding a grouted diaphragm that penetrates the full height of the dam combined with a toe drain is recommended to rehabilitate earth dams.