Soil Reinforcement with Natural Fibers for Low-Income Housing Communities
Total Page：16
File Type：pdf, Size：1020Kb
Project Number: LDA-1006 Project Number: MT- 1003 Soil Reinforcement with Natural Fibers for Low-Income Housing Communities A Major Qualifying Project Submitted to the Faculty of WORCESTER POLYTECHINIC INSTITUTE In partial fulfillment of the requirement for the Degree of Bachelor of Science By _________________________ Bryan Gaw _________________________ Sofia Zamora Approved by: ________________________ Professor Leonard D. Albano, Co-Advisor _______________________ Professor Mingjiang Tao, Advisor 1 Abstract The objective of this project is to identify a natural fiber to enhance the shear strength and bearing capacity of a cohesive soil. This study includes a proposed protection method to increase the durability of the selected fiber, determination of the optimum reinforcement scheme in terms of fiber’s content and length, and investigation of the reinforced soil through laboratory experiments on footing bearing capacity and slope stability analysis. 2 Acknowledgements We would like to thank the following people for their role in helping make this project a success: Don Pellegrino - Laboratory Manager Dean Daigneault – Laboratory Manager Leonard Albano – Associate Professor of Civil and Environmental Engineering Mingjiang Tao – Assistant Professor of Civil and Environmental Engineering 3 Authorship Page This report was authored by the following individuals, each had specific authorship responsibilities and each collaborated between disciplines across the completion of the project. Bryan Gaw ______________________________ - Selection of protection method. - Testing implementation. - Preparation of test specimens and testing. - Co-analyzing data. - Authorship of Background and Methodology. - Editing. Sofia Zamora ______________________________ - Selection of reinforcement method and natural fiber. - Planning of experimental implementation. - Design of special devices for tests. - Preparation of test specimens and testing. - Co-analyzing data. - Modeling and analysis of implementation. - Cost estimation. - Authorship of Introduction, Analysis and Results and Applications Chapters. - Formatting and editing. 4 Capstone Design Statement The capstone design criteria aim towards driving the students through a decision making process where the solution to a problem is developed though synthesis and analysis of different aspects that shape the final solution design. The main eight realistic constraints that shaped the design process during this project are the following: economic, environmental, sustainability, constructability, ethical, health and safety, social and political. The economic and social constraints were the leading aspects in the design of the project. The social constraint determined the population we aimed to provide a solution for. We are aware of the large disparity among social classes in developing countries and the low living standards this brings to the poorest communities; therefore we decided to focus on the poorest social groups in these countries. Our main concern is the high-risk conditions in which these communities develop their housing. The project focuses on beginning to develop a solution for these communities to establish on hillsides under safer conditions. We determined the improvement of safety required the stabilization of the ground to be developed. The scarcity of resources available to these communities made the economic constraint the leading criteria in the selection of the soil reinforcement method. We evaluated different reinforcing methods and selected the most feasible one for these communities. Therefore we studied a method that properly reinforced a cohesive soil type, commonly encountered in developing nations and that required inexpensive, locally attainable materials and minimal construction effort and machinery. The environmental and sustainability constraints were also part of the core design. The environmental constraint determined the materials and process used for the reinforcement method. We selected natural fibers, and used a 100% natural protection method for the selected fiber, because we wanted to prevent contaminating the soil with detrimental materials. Following the environmental concept of reducing drastic modifications to the landscape as to not disrupt the existing ecosystem, we aimed to sufficiently increase the shear strength of the soil in the slope to minimize the grading process and the change in runoff. The sustainability constraint determined our design approach. Our design aimed to provide a 5 reinforcement method which at the end of its useful life would become an asset to the soil while allowing other stability methods to come in place. Therefore we selected biodegradable materials which will not endanger the species or the type of organisms that inhabit in the area. The key aspect of the design became to provide a temporary solution while a more permanent but equally sustainable solution could be implemented. An example of such a method is planting a specific species of tree capable of growing strong widespread roots during the lifespan of the fiber reinforcement. The roots of the trees only need to hold the upper 3 or 4 feet of soil. The design aims to behave as an item in a closed ecosystem cycle. The constructability constrains the manner how the fibers would be implemented. We evaluated the construction resources available to the target-users and we determined the most feasible implementation would be by mixing the fibers into the soil instead of inserting layers of fiber fabric or ties. We evaluated the difficulties of the soil removal, fiber preparation, and soil mixing and compaction and provided a basic cost and schedule estimate. We designed a basic reinforcing method through the modeling of grading, soil compaction and basic drainage. The models evaluate the increment in factor of safety of the slope when the reinforcement is in place. The models were modified iteratively aiming to minimize the required depth of reinforcement while the increase of factor of safety remained acceptable. The health and safety constraint shaped the criteria by which the reinforcement method was deemed successful. The fibers and the components of the protective coating were selected based on their toxicity reports. All of the materials are non-toxic. Also, as described in the previous paragraph, the reinforcement models were deemed successful when they had a factor of safety larger than 1.1. This extra 0.1 accounted for the peak load concentrations that could occur during the construction process. The design of the bearing capacity test and the models, were done in compliance with the safe dimensions dictated in the Central American Building Code,1996 . The political constraint dictated the Construction Manuals and Building Codes that were consulted in order to comply with the construction practices allowed in the focus areas. Also, in 6 recognition of the political atmosphere in these communities, we simplified the communal decisions and collective work required for the implementation of the reinforcement. The ethical constraint lead to us to complete this project according to Code of Ethics for Engineers, 2003. According to the 6th Fundamental Canon, we conducted ourselves honor ably, responsibly, ethically, and lawfully so as to enhance the honor, reputation, and usefulness of the profession. We determined our conclusions and recommendations according to the Professional Obligations One and Two. 7 Table of Contents Abstract ........................................................................................................................................... 2 Acknowledgements ......................................................................................................................... 3 Authorship Page .............................................................................................................................. 4 Capstone Design Statement ........................................................................................................... 5 List of Figures ................................................................................................................................ 10 List of Tables ................................................................................................................................. 12 Chapter 1: Introduction ................................................................................................................ 14 Chapter 2: Background ................................................................................................................. 19 Current Soil Stabilization Technologies ..................................................................................... 20 Effect of Soil-Fiber Reinforcement on Soil Shear Strength ....................................................... 25 Important Impact of Soil-Fiber Reinforcement: Improvement of Soil Bearing Capacity ......... 27 Chapter 3: Methodology ............................................................................................................... 31 Selection of Fiber and Experimental Design Parameters .......................................................... 31 Selection of Testing Sequence and Procedures ........................................................................ 32 Soil Selection ............................................................................................................................. 35 Soil Synthesis ............................................................................................................................