Surcharge preloading consolidation of reclaimed land with distributed sand caps

For land reclamation using the conventional surcharge preloading method, a sand cap layer is often fully placed at the ground surface of ultra-soft compressible estuary or marine clays. A novel strategy of distributed sand caps is proposed to save cost associated with sand materials. At an early stage of consolidation, the drainage capacity of distributed sand caps is less than the drainage demand, whereas at a later stage, the capacity exceeds the demand. Hence, the overall drainage capacity of distributed sand caps is equivalent to the drainage demand. A numerical model is developed to study the effectiveness of the proposed technique, and calculations are compared against theoretical solutions. A parametric study is conducted to optimize design parameters. It has been found that distributed sand caps should be uniformly placed with a size of 3% of the total width and a spacing of 1 times the size, such that sand materials can be saved by up to 50% without compromising the consolidation efficiency (an increase of consolidation time by less than 5%). The use of distributed sand caps will be effective regardless of soil properties, including hydraulic conductivity, elastic modulus and Poisson's ratio.