The Shear Properties of Clay Mixed with Crushed Glass Using CBR and Triaxial Analysis - Report Example

The analysis of the shear properties of clay mixed with crushed glass using CBR and triaxial analysis Introduction The quality of the soil subgrade influences the performance of the pavement. A pavement can last for long if the pavement has proper draining and stable soil. Roads constructed in soil areas usually experience pavement failures in form of depression, unevenness and cracking. This is caused by low shear strength that can reduce further on physical disturbances or wetting. Geotechnical engineers have been studying the soil subgrade in an effort to establish the best method for soil improvement and soil stabilization. Thus there has been a rise in research on soil improvement techniques for construction and engineering projects. Material reuse is one of the alternative methods that are more economical for application of soil stabilization. Soil stabilization is the process of mixing and blending materials such as waste materials with the soil to improve its engineering properties. Soil improvement enhances properties such as compressive strength, bearing capacity, the shear strength parameters and soil cohesiveness. The major problem in using crushed glass is lack of knowledge about geotechnical properties of these materials and their effects on the environment. Different research has been done to determine if the material can be a substitute for traditional techniques of soil improvement like cement and lime. An example of their application includes the use of a mixture of glass with sand on Florida beaches. The increase in the shear strength property of the soil has a number of benefits. They include increase in bearing capacity, ground improvement, slope stability and soil stabilization. Currently, large amount of recycled materials consist of glass, providing an opportunity to use recycled crushed glass materials for engineering construction. Triaxial testing and CBR testing are used to study the effectiveness of crushed glass materials for improving the shear properties of the soil. Project objective and deliverable The main deliverables for this project is to bring a new knowledge and understanding on the improvement of clay through the application of crushed glass. The knowledge gain from this test can be used is real life application. It is expected that the mechanical properties of the sample with crushed glass will have improved. The specific deliverable will be to determine the optimal percentage of the crushed mixture of soil and glass to obtain the desired properties in the soil’s shear characteristics. Moreover, the optimum sizes of the particles will determined, so as to establish if medium or fine categories of crushed glass are the best. The project will not only improve the soil properties, but it also reduces the amount of waste being dumped in land fill. This will also assist in the conservation of the environment. Specific project aims The study focuses on increasing the shear properties of soil samples that have been mixed with crushed glasses, compared to the samples that have not been improved through the introduction of crushed glass. The main aims for this project include: To conduct test on reinforced soil and control samples with different amount of fibre. To compare the results of the test of the samples with varied fibre content Produce a conclusion of the overall project Project benefits and implications The benefits derived from using crushed glass so as to improve the shear properties of the soil will be: a) Provide an alternative to the old techniques Crushed glass exhibit improved levels of shear and workability properties and can be used as a substitute for gravel and sand in the construction of roads, pavements and road design. Experiment has shown that crushed glass for road design has not leaching problem, therefore, cannot affect the environment negatively. It also has a potential to provide another alternative to traditional ground improvement methods such as cement/lime stabilization soil preloading and soil reinforcement b) Increase slop stability Improvement in the shear properties of the soil by mixing with crushed glass will result in greater stability of slopes. Consequently, the safety factor in design of embankments and slope design will be reduced, thus reducing the cost of the project. c) Reduced non-biodegradable waste being dumped in landfill Preservation of the environment is the key issue in the modern world. The engineers should be involved in the accomplishment of this goal, by designing systems that can reduce waste. Glass wastes are non-biodegradable, thus, by recycling waste glass materials through soil reinforcement, they not only produce improved engineering properties, but it also reduces waste going downhill. d) Improved shear properties of the soil There will be an increase in shear angle and strength for the soil. This affects a wide range of application such as foundation design and structures that require bearing capacity. Research has shown that the shear properties are improved with the introduction of fibre in the soil sample (Shivanand and Signh, 2013). e) Reduction of cost for projects Since geotextiles are very expensive, by utilizing waste materials, soil with the same strength characteristics can be obtained with little cost. The waste glass materials can be obtained easily compared to other materials that are processed. Key research literature based rationale, justification and significance of the body The concept of geotechnical fibre reinforcement in design involves the use of reinforcing materials to increase the shear strength of the soil, resulting in slope stability. Andersland and Al-Khafaji (1992) investigated the effects of reinforcement material in the soil properties. They utilized triaxial tests on kaolinite clay mixed with cellulose pulp fibre. They found out that the shear strength obtained under various conditions that include consolidated undrained, consolidated drained and undrained, increases with increase in the fibre content. Similarly, they found that the failure mode changed from brittle to plastic. The ductility of the sample also increased significantly with an increase in fibre content (Al-Khafaji, 1992). Shivanand and Signh (2013) conducted a study to explore the shear strength parameters for sandy soil that has been mixed with glass. The study utilized triaxial testing technique to observe shear properties, strain behavior, and volume change of the soil sample. They found out that the shear stress to the horizontal strain for the samples showed an increase in the shear angle, soil cohesion and soil density. The research shows an improvement in soil properties through soil reinforcement with glass fibres. The present study use a different soil type that the one used in the study, but the study indicates that glass can be used as a geotechnical engineering material (Shivanand and Signh, 2013). Disfani et al., (2011) investigated the effects of recycled crushed glass on the environment when they are used in the construction of road. They conducted their test in accordance to the geotechnical tests and environmental agencies tests and found out that the recycled crushed glass has improved properties in relation to the shear strength, hydraulic conductivity and workability compared to natural aggregate samples. They also found out that the materials do not have any potential to cause leaching hazards. The research is significant as it shown the effects of the crushed glass materials on the environment (Disfani et al., 2011). A comprehensive study carried out by Gray (2003), utilized three point bending and unconfined compression test on kaolinite clay sample that was reinforced with fibre. He found out that random distribution of the fibre increase the compressive strength of the specimen. The flexural toughness, tensile strength and ductility of the kaolinite clay also increased. The effectiveness of fibre reinforcements were seen to be more in sample with low moisture content (Gray, 2003). Similar research on the utilization of fibre to increase the properties of cement was done by Consoli et al. (1998). They note that fibre content is shown to increase the residential shear strength and decreases stiffness. Consequently, the sample changed from being brittle to being ductile (Consoli et al., 1998). The rationale for this project is study the alternative technique for soil improvement. There has been an increase in demand for the use of land, with less than ideal geotechnical properties, for building and development. Therefore, various researches have been conducted to provide alternatives for ground stabilization. This research has a potential to improve the mechanical properties of soil to be applied in various applications, that may include application where increased shear angle and shear strength are required. The methods utilized are reliable and provide accurate results. The application includes ground improvement, foundation design, roads and other applications which require bearing capacity. Brief research strategies / approach The technique used in this study will mainly be based on experiment that will be conducted for different soil sample. The techniques that will be used are triaxal testing technique and California bearing ratio (CBR) technique. Soil samples that will be used in this test will be obtained locally as they are easily available. A range of soil samples will be collected that will be sufficient for preparing the samples and conducting the test. To ensure that soil properties such as moisture are not affected, the samples will be kept in air tight bags. The immediate data like the date, location weight and time will be recorded for each sample. To ensure that the required standards are met, the experiment will be conducted in accordance with AS 1289 for sample preparation and testing of soil samples. Recycled crushed glass will also be obtained. The physical properties of the soils samples such as moisture content, void ratio, and bulk unit weight are determined before mixing them with crushed glass. These values will be essential in the analysis of the result and determination of information relating to the test. Some samples will be mixed with crushed glass of varying gradation and sizes. This enables a perfect amount of crushed glass and gradation to be tested. A sample will not be mixed with crushed glass to facilitate the comparison between the soil samples. Thus improvement factor will be determined. Small test will be conducted before conducting the triaxial testing. This is done in order to determine the basic parameter of the sample such as particle sizes, material classification and moisture content. Particles sizes will be determined through sieve analysis on the sample. Moisture content is also determined through compaction test. To ensure more reliable and accurate results, both the undrained and drained shear strength will be measured. This is accomplished by performing three tests on the sample depending on the drainage and the loading condition, which include unconsolidated undrained (UU) triaxial test, consolidated undrained (CU) triaxial test and the consolidated drained (CD) triaxial test. Triaxial testing will be conducted according to the Australian standard AS 1289.6.4.2. The pore water pressure is determined which the calculation of the effective stress on the sample. Triaxial tests will be conducted in three phases, which include full saturation of the sample, application of pressure to consolidate the sample, before compressing it to obtain shear properties. During the consolidation, a pressure of 400kPa will be used with 150kPa back pressure. The Deviator stress and the friction Angle (Φ) are obtained by measuring the minimum and maximum stresses at failure. The axial and vertical stress is increased until the sample fails depending on different axial and lateral stress. Since the drainage condition of a sample affects the results, the drainage is prevented in undrained test (Fang, 1997; Preene, 2012). CBR test will be conducted in accordance with the Australian standard AS 1289.6.1.1. Samples are placed in a tank for 4 days before conducting the test. The results obtained will give a relative strength of the soil sample used in pavement or roads design application. Initial timeline The proposed timeline for this project was developed so that the task and the entire project is completed within a given time limit as shown in the table below. From the table, Gantt chart was created as shown below. The table showing the timeline Week no. Supervisor meeting Tasks The 1st project 1 Project proposal 2 1st meeting 3 4 2nd meeting 5 Project writing 6 7 8 3rd meeting 9 Oral presentation 10 4th meeting Final report writing 11 Submit report 12 Exam period 13 14 Break Soil testing The 2nd project 1 2 3 10 Writing thesis 11 Submitting the thesis That table for Gantt chart Task Start date Duration The 1st project 10/3/2015 60 Project specification 10/3/2015 5 Submitting specification 14/3/2015 1 Project proposal 30/3/2015 20 Submitting proposal 19/4/2015 1 Prepare presentation 10/4/2015 10 Presentation 20/4/2015 1 Final report 10/5/2015 30 Submitting the report 10/5/2015 1 The 2nd project 15/7/2015 80 Experimental work 31/5/2015 41 Thesis writing 28/7/2015 40 Submitting thesis 5/9/2015 1 Prepare poster 10/9/2015 25 Poster presentation 5/10/2015 1 The experiemnt will be conducted in the laboratory. A meeting with the technician will therefore be necessary, to plan on how to perform the experiment and to make sure that triaxial and CBR testing machines are in good condition. The expense will cover for labour, transport and and materials used to collect the samples. The main cost associated with experiment is the processing of crushed glass and mixing them with sample to be improved. References Al-Khafaji, A. W., & Andersland, O. B. (1992). Geotechnical engineering and soil testing. New York: Oxford University Press Consoli, N.C.; Prietto, P.D.M.; and Ulbrich, L.A. (1998). Influence of fiber and cement addition on behaviour of sandy soil. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 124(12), 1211-1214. Disfani, M. M., Arulrajah, A., Bo, M. W., & Sivakugan, N. (January 01, 2012). Environmental risks of using recycled crushed glass in road applications. Journal of Cleaner Production, 20, 1, 170-179. Fang, H. Y., (1997). Foundation engineering handbook. New Delhi: CBS Publishers & Distributors. Gray, D.H. (2003). Optimizing soil compaction and other strategies. Erosion Control, 9(6), 34- 41. Preene M., (2012). Groundwater Lowering in Construction: A Practical Guide to Dewatering, Volume 6 of Applied geotechnics, 2nd ed, CRC Press, Shivanand, Singh, S, B, (2013). A study on shear strength of sand reinforced with glass fibres. International Journal of Scientific & engineering research, 4, 285-288 Read More