Application of Deep Mixing and Stone Column Techniques for stabilization of Large Earth Cum Rock Fill (ECRF) Dam for an Irrigation project-PPT Presentation

PPT Presentation

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The presentation describes the use of Deep Soil Mixing (DSM) to stabilize the 1,750 m-long Earth-Cum-Rock-Fill dam at the Polavaram irrigation project on the Godavari River in Andhra Pradesh, India. DSM was introduced by Bauer for the project as a sustainable alternative to conventional ground-improvement methods.<br /><br />DSM mixes self-hardening binder slurry with in-situ soil to create stronger, stiffer columns. The columns were designed beside the existing plastic-concrete cutoff wall, providing an intermediate stiffness between the wall and stone-column-treated ground. This transition is intended to improve ground stiffness, reduce differential deformation, and protect the cutoff wall. The target was to increase initial soil stiffness fivefold.<br /><br />Trial works comprised 18 columns, each 1 m in diameter, spaced 1.3 m apart in a square pattern, with a treatment-area ratio of 40%. Columns were installed using a wet, single-auger mixing method. Quality assessment included collecting samples at different depths and testing their unconfined compressive strength and deformation modulus. The specified 28-day characteristic compressive strength was 0.5–1.0 MPa, with a target deformation modulus of 40–135 MPa.<br /><br />Design studies used Plaxis 2D to model staged construction, soil treatment, dam construction, and reservoir filling. A 10 m transition zone between DSM and stone columns was designed, incorporating five rows of DSM columns. Predicted maximum settlement was 48 cm before reservoir filling and 50 cm afterward for the lower-bound case; corresponding upper-bound values were 46 cm and 48 cm.<br /><br />The presentation concludes that DSM can reinforce and protect the cutoff wall, improve ground stiffness, and provide a sustainable ground-improvement option for large dams.

Keywords

Deep Soil Mixing

DSM

Polavaram irrigation project

Earth-Cum-Rock-Fill dam

Godavari River

ground improvement

cutoff wall

geotechnical engineering

settlement analysis

Plaxis 2D