Model tests of prefabricated horizontal drains with vacuum preloading on clay slurry for land reclamation

• Main Author: Teo, Brenda, Jia Wen
• Other Authors: Chu Jian
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/67463
• Institution: Nanyang Technological University

With the upcoming plans for the development of the country, Singapore needs to increase her territory to keep up with the economy. Singapore reclaims land to increase her land space. However, Singapore has a drastic lack of land fill materials because her resources have been depleted. Singapore has been searching for materials and exports from other countries to fill up the shortage of materials. Recently, import bans were imposed on her and hence, she has to explore other materials to use for land reclamation other than using the typical materials, sand and gravels. Cohesive soils such as marine clay have been studied to replace the usual materials because cohesive soils have different properties as non-cohesive soil. Cohesive soils display large settlements and have low bearing capacities. Soil improvement methods are needed to strengthen cohesive soils and to increase the rate of consolidation. Hence, this project aims to improve the properties of cohesive soils by proposing the use of vacuum preloading and prefabricated horizontal drains. The objectives of this project are to investigate the effectiveness of vacuum preloading and prefabricated horizontal drains on the rate of consolidation of clayey soil in a settlement tank test and to test whether the addition of lime on clayey soil is effective to increase the rate of consolidation. The prefabricated horizontal drains used in this project are a combination of prefabricated vertical drains with geotextile sheet. Preliminary tests were conducted and the results were analyzed. The purpose of the preliminary tests is to test the effectiveness of the addition of lime. After the preliminary tests, kaolin was chosen as the tested material. No lime was added and water content of 160% was selected for the settlement tank test on the effectiveness of the proposed method. Laser sensors and pore-water pressure transducers were used in the settlement tank test to monitor the surface settlement and to measure the pore-water pressures. In addition, shear vane test was conducted and water content of different points was obtained. Based on the findings and results of the settlement tank test, it is concluded that the proposed method of using vacuum preloading and prefabricated horizontal drains is useful in helping to consolidate clayey soil. The degree of consolidation is calculated and it corresponds to the results of the rate of settlement and pore-water pressures. However, more in depth studies and experiments are required to prove that the proposed method works. One-dimensional consolidation is assumed in this project, but in reality more factors and parameters are to be considered.