Grouting in Ground Improvement – Effects and Definition Which of the following statements about grouting in coarse-grained soils is/are correct?

Introduction / Context:
Grouting is a common ground improvement technique used to reduce permeability, control seepage, and enhance strength/stiffness of soils and weak rocks. It is frequently applied below dams, around shafts, and beneath foundations to mitigate piping or settlement and to improve bearing capacity locally.

Given Data / Assumptions:

• Target soils are typically coarse-grained or fissured media where grout penetration is feasible.
• Grout types include cementitious, chemical, microfine, and polyurethane, among others.
• Objective may be seepage control, void filling, or structural improvement.

Concept / Approach:

By injecting grout under pressure, interconnected voids are partially or fully filled, thereby reducing the hydraulic conductivity and increasing interparticle bonding. This often elevates the small-strain stiffness and shear strength. The process definition itself is the injection of grout into the pore space or fractures to achieve the desired performance outcomes.

Step-by-Step Solution:

Verification / Alternative check:

Permeability tests before/after grouting and in-situ shear/penetration tests typically show reduced k and enhanced strength/stiffness.

Why Other Options Are Wrong:

Each of (a)–(c) is correct; 'All the above' captures the complete picture.

Common Pitfalls:

Attempting to grout very fine silts/clays with coarse cement grouts; inadequate pressure/volume control causing hydrofracture or heave.

Final Answer:

All the above