Rheological properties of sand-foam mixtures used in Earth Pressure Balance tunnelling

  • Qiong Zhang

Student thesis: Master of Philosophy

Abstract

Earth Pressure Balance (EPB) tunnelling machines are commonly used for tunnelling in soft grounds. Soil conditioning agents such as foams and polymers are increasingly used to modify the properties of the soils in order to make to them easier to be excavated and transported by EPB machines. Previous researchers have mixed foam agents with different soils and assessed the properties of foamed soils using a variety of procedures including slump, screw conveyor model, rheometer tests. These studies have focused on the effects of conditioning agents on the properties of the soils, but with little consideration of the foam generation process itself or accurate measurement of the properties of foams. The test methods for basic foam properties reported in existing research are all based on EFNARC (2005), which itself is based on research originally undertaken for firefighting foams. This may not only miss important aspects of the foam conditioning process but it can also make it difficult to compare the results of different research programmes. This thesis presents the results of an experimental investigation of the basic properties of foams and sand-foam mixtures. Considerations have been given to correlation of control parameters such as air line pressure and tank pressure in foam generating process. In addition, the effects of air/liquid flow rates and the ratio between air and liquid flow rates on the foam properties have been studied. For the purpose of developing advanced experimental methods for a more accurate assessment of foam properties, a specially designed setup for bubble size measurement and continuous foam fractionation process has been developed. Results are presented and the possibility of measuring foam stability and the liquid fraction of foams with the setup is introduced. At last, design and development of a soil rheometer which is capable of measuring the viscosity of sand-foam mixture are presented. Contents such as the process of design, results from trials with sand-foam mixtures, alignment process and proving tests are included.
Date of Award1 Aug 2018
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorAhmad Syed Mohd Syed (Supervisor) & Majid Sedighi (Supervisor)

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