Technical Paper
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Table of Contents:
Overview
Definitions
Calculations
Technical Data
Section 1 What is Soil?
Section 2 Atterberg Limits and Triaxial Index
Section 3 Additives and Cohesionmeter
Section 4 Flexible Pavement System 19W
Section 5 Different Types of Design Structures
Section 6 The Design Chosen
Overview
This research will explain an efficient and cost effective procedure in constructing Farm to Market highway 44. To come to the conclusion that any Farm to Market road with these conditions of environment, expense and budget limits will be more cost effective to rework the existing structure and then stabilize the existing base with cement and then apply a Two Coat Surface Treatment. Prior to arriving to this conclusion, it will be necessary to define soil, the plastic and liquid limits, plasticity index, and the triaxial class. By determining these factors, it will be essential to perform simple experiments to find the moisture content of the subgrade. By finding the plasticity index, it enables the triaxial class to be identified. After, gathering the needed information you can enter the information into the computer program FPS19W. This program will provide the information such as stabilized subgrade depth, the needed base depth, and top surface depth. In order to analyze the data of the five comparisons properly it is necessary to create a table to where it shows the cost and materials used in an easy to understand table. Finally, after thoroughly analyzing the table information it is now possible to choose the most structurally efficient, and cost effective design structure.
Definitions:
Soil – Any earth material except embedded rock or shale that will crumble within a short time when an air-dried sample is place in water and agitated
Liquid Limit (LL) – the boundary between the liquid and plastic states. This limit is determined based on the Number of blows required to cause a groove to close in a sample.
Plastic Limit (PL) – The boundary between the plastic and semi-solid sates. The limit is determined as the point at which a thread of soil of a specified size begins to crumble.
Plasticity Index (PI) – the difference in moisture content between the liquid and plastic limits
Plasticity – The Ability of a soil under certain moisture conditions to be deformed without cracking or crumbling and then maintain that deformed shape after the deforming pressure has been released.
Triaxial Index – A number that states the soils stability
FPS19W – A computer program that gives information based on algarithisms. From information that it is given
Calculations
Liquid Limit (LL)
Plastic Limit (PL)
Mass of water:
Plastic Limit (%)
Plasticity Index
Where:
A = mass of wet soil + tare, g
B = mass of dry soil + tare, g
C = mass of tare, g
Section 1
What is Soil?
In the general since of engineering, soil is defined as the uncemented aggregate of mineral grains and decayed organic matter along with the liquid and gas that occupy the empty spaces between the solid particles. Soil, known as subgrade for the purposes of designing and construction of a road, gives the pavement structure support. There are three different kinds of soil, the smallest are clay and silt, and the largest is sand.
Characteristics of clay are that it is cohesive and plastic. Clay has several unique physical properties. One is that it is able to absorb large quantities of water; clay can be made into clay pots, bricks, etc Clays ability to absorb water gives it shrink-swell properties. Clay expands when water is added and shrinks as it dries. When clay is wet, its expansion sometimes causes the roadway to fail. Also when saturated with water the clay losses its ability to bare the weight of highway equipment. When clay is dry, it will shrink. The clay will develop cracks. These cracks may propagate up into the roadway. If clay is too hard, it creates problems when trying to break up the existing structure.
Silt particles are the second largest. Like clay particles, they are also invisible to the naked eye. Silt is a fine textured soil like clay – able to absorb water, but only in small quantities, and has a small shrink-swell factor.
Sand due to its large particles unlike clay is visible to the naked eye, making it cohesion less and non-plastic. Sand is the most permeable of the three types of soils. Water is able to permeate through sand very easily. This gives it relatively little or no shrink-swell factor. The reason that sand is able to absorb little or no water is that the individual sand particles are so large that they do not touch on all sides Due to this in, some places large gaps or spaces where the water seeps through easily. Since moisture occupies the soil for a short time, the soil is unable to expand. In view of the fact, that sand has such a small shrink-swell factor,