Surcharge preloading consolidation of reclaimed land with distributed sand caps

Abstract

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.

Keywords:

• Distributed drainage boundary
• sand caps
• surcharge preloading
• consolidation
• finite element analysis

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant 51578164), the Natural Science Foundation of Guangxi Province (Grant 2016GXNSFGA380008), and the Ministry of Education of China through the Changjiang Scholars Program to Dr Guoxiong Mei, and the National Natural Science Foundation of China (Grant 41672296) to Dr Yanlin Zhao.