Wall movement due to jet grouting

• Main Author: Goh, You Tian.
• Other Authors: Wong Kai Sin
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/40211
• Institution: Nanyang Technological University

Jet grouting is often used as a technique for in-situ soil improvement in many types of soils, especially soft clays in Singapore. Among of its many applications, the common use is to improve the ground for excavations to prevent excessive wall movements. The objectives of this research are (i) to investigate the causes of wall and soil movement due to jet grouting. (ii) To examine whether it can be simulated in the finite element analysis and (iii) to investigate the main parameters affecting the wall movements. The main cause of wall and soil movements is due to the choking of annulus and not the direct result of high pressure jetting. Thus to have a clear understanding of this effect on the wall, three case studies have been back-analyzed using the finite element software, Plaxis version 8.2, to model the entire construction process. Results indicate that it is possible to simulate such construction. Monitored measurements from each case study were compared with FEA results. They were found to be in good agreement. This allows the design engineers to anticipate potential problems which could occur on site. Unfortunately, there is no exact range of artificial pressure that can be adopted in the design. A range of pressure must be tested to achieve the desired results. Extensive parametric studies were conducted on the effect of varying clay thickness, jet grout pile’s (JGP) thickness, fill thickness and JGP location at increasing artificial pressure. Results indicate that these factors are sensitive factors affecting wall and soil movements. It is interesting to note, that a thick JGP located at a shallow depth of 10 to 15m below ground surface will induce a cantilever-liked shape of deflection. Such deflection shape registers a higher magnitude of wall deflection as compared to other form of deflected shapes. Throughout this research, referencing of the wall movement was made using net movements of the deflected wall profiles. This is the difference between any two points obtained from the inward deflected curve to the outward deflected curve. Such method of accounting of wall movements ensures certain standard of practicality while not being overly conservative.