Expansions of ten percent or more are not uncommon. Less than 50% of clay contents having high swelling potential. The presence of expansive clays can be detected by. Differential thermal analysis and xray diffraction pattern analysis have shown that montmorillonite mineral is predominant in expansive soil 1. Expansive soils, an evaluation of methodology for prediction and minimization. This enables the soil to soak up water in large quantities, which results in an increase in the soil s volume. Pdf guidelines to identify and quantify expansive soils in civil.
Foundation materials that exhibit volume change from change in soil moisture are referred to as expansive or swelling clay soils. When expansive soils obtain moisture, they expand or swell up. The more water they absorb, the more their volume increases. In southern utah, blue clay primarily occurs within the upper member of the chinle formation. Problem soils right repeated shrinking and swelling ofclay produces a char acteristic popcorn texture. Expansive soils owe their characteristics to the presence of swelling clay minerals. Institution of civil engineers manuals series core. Green part of unit generally less than 50% consists of clay having slight to moderate swelling potential. Expansive soils are soils that have the ability to shrink andor swell, and thus change in volume, in relation to. As they get wet, the clay minerals absorb water molecules and expand. An expansive clay is one which is relatively free of impurities such as sand, silt, and organic material, and which has the capability of absorbing large quantities of water during prolonged periods of rainfall or flooding. Expansive soil stabilization a pdh online course for.
Expansive spoil is distinguished by the presence of swelling clay minerals that can absorb a significant amount of water molecules. This enables the soil to soak up water in large quantities, which results in an increase in the soils volume. Stabilization of shallow slope failure on expansive clay. Likewise, when expansive soils lose moisture, they begin to shrink.
Expansive or swelling soil is a highly plastic soil that normally contains montmorillonite and other active clay minerals. The soil contracts due to its clay minerals and the structure of the clay allowing water to be imbedded inbetween the clay layers process is reversible, and causes contraction of the soil black cotton soils properties. Because it has strong hydrophilic mineral composition, its engineering prosperities embodies that its shape contracts under dehydrating, inflation and softening under the influence of water and the strength attenuates. There are four types of clay soil that differ in characteristics depending on the amount of clay in the soil. Expansive soil is a commonly identified problem which has. Expansive soils and foundation damage by jes foundation repair. In the field, expansive clay soils can be easily recognized in the dry season by the deep cracks, in roughly polygonal patterns, in the ground surface see fig.
Land areas were assigned to map soil categories based upon the type of bedrock that exists beneath them as shown on a geologic map. Erh erm erl areaof highly expansive soil or rock 5 percent swell in the shallow subsurface expansive soils f. Geotechnical differing site conditions, fhwa1996, view pdf. Swelling properties of expansive soils treated with chemicals. This soil is common to many parts of the world, limiting what homeowners, gardeners, and farmers can grow. Optimal moisture and maximum dry density measurement for types of soil soil type description opt. Blue clay soil is a type of expansive soil characterized by its bluishpurple color and high absorptive property. Geotechnical aspects of buildings on expansive soils in kibaha. Swelling clays can control the behavior of virtually any type of. Environmental systems engineering, university of regina, regina, sk, canada abstract. The typical clay soil profile in the areaconsists of 2 3 m of dark grayish brown clay layer underlain by reddish brown claylayer down to a depth of 10 m. Expansive soils generally called as black cotton soils covers nearly twenty percent of the geographical area in india. Swelling pressure and retaining wall design in expansive soils. Testing, evaluation of selfboring pressuremeter tests in boston blue clay.
Yellow data insufficient to indicate clay content of unit andor swelling potential of clay. Feb 12, 2016 in this pro tip episode ill give you a way to know if the soil under your property has a high clay content, and ill talk about why expansive clay can wreck havoc on your concrete foundation. Engineering properties of an expansive soil proprietes mecaniques dun sol gonflant azam s. Native backfill soil shall not consist of expansive clay. And if you have been around for even longer, there is a greater chance you have seen the effects of blue clay. The different percentages of clay soil include silt soils which have 0 to 10 percent clay, clay soils with 10 to 25 percent clay, clay soils with 25 to 40 percent clay and clay soils with 40 percent clay. In order to determine the soil shrinkage and swelling. This four hour online course discusses guidelines and criteria for modifying and stabilizing expansive clay soils by various methods. Key aspects that need identification when dealing with expansive soils include. Expansive soils present significant geotechnical and structural engineering challenges the world over, with costs associated with expansive behaviour estimated to run into several billion annually. In this pro tip episode ill give you a way to know if the soil under your property has a high clay content, and ill talk about why expansive clay can wreck havoc on your concrete foundation. The maps included with the survey indicate what soil type or types exist in the vicinity of your project. An expansive clay soil does not change in volume unless it undergoes a change in moisture content, and therefore, it is of prime importance to know how moisture moves in clay soil and how soil properties and climatic conditions affect the speed of moisture flow. The results indicated that the percent swell is intimately related to the amount of water that is adsorbed by the expansive clay minerals.
This expansive soil has the ability to severely damage roads, building foundations and sidewalks. Pdf expansive soils present significant geotechnical and structural engineering challenges the world over, with costs. There are a couple of preliminary methods you can use when you inventory a site. This video shows how to test soil to determine if there is enough clay content to use the soil for construction cob, adobe, clay plasters, and more. First, identify if the soil on your clients site is expansive. Clay soil is a very dense substance that can cause major drainage problems for your plants. Swelling clays and septic systems, rw3w purdue extension. Mechanisms of stabilization of expansive soil with. This type of soil contains minerals like smectite clays, which absorb a lot of moisture. Clay is a finelygrained natural rock or soil material that combines one or more clay minerals with possible traces of quartz sio 2, metal oxides al 2 o 3, mgo etc. Shrinking and swelling soils can damage homes, roads, utilities, and septic systems. Clyde armstrong natural hazards cause billions of dollars of damage to trans portation facilities each yearonly flooding causes more dam age than expansive soils. Expansive soils, clay soil, shrinkswell, and heavable soil. Native backfill is defined as granular soil excavated from a trench and it shall be free of ice, clay, debris and excessive organic matter.
Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Furthermore, the amount of moisture in an expansive soil is influenced by a small addition of organic cationic compound such as ls. Expansive soils are often referred to as swelling clays because clay materials are most susceptible to swelling and shrinking. Expansive clay is a clay soil that is prone to large volume changes swelling and shrinking that are directly related to changes in water content. A retaining wall constructed on expansive soil can be subjected to lateral swelling pressures due to soil swelling, which may cause a significant horizontal deformation and bending of the retaining wall. Expansive soil and rock contain a significant percentage of clay minerals that can.
In australia, it is generally assumed that the backfill behind a retaining wall is non expansive material. Erhbedrock units with high shrinkswell susceptibility, blue clay. Engineering characteristics of expansive soil and its. In most areas, where soils are produced in situ, this method of assignment was reasonable. Damage to structures in arizona is commonly related to soil characteristics, with expansive shrinkswell soils and collapsing soils caus ing the most problems. However, some areas are underlain by soils which have been transported by wind, water or ice. Swelling clays and septic systemsrw3w purdue extension darrell schulze, purdue agronomy phillip owens when soils are moist, the negatively charged surfaces of 2.
Cns layer creates an environment similar to that around 1 m deep in an expansive soil with equivalent cohesion to counteract heave. Expansive soil and rock contain a significant percentage of clay minerals that can absorb. Expansive soil clay guidelines methylene blue uruguay. The completion of the above is followed by visualmanual descriptive of the. Expansive soils contain minerals such as smectite clays that are capable of absorbing water. Swelling properties of expansive soils treated with. The focus of this study was based on existing knowledge that expansive, or swelling, clays can cause performance problems in pavements whose coarse aggregate fraction contains an appreciable amount of clay. Institution of civil engineers manuals series nerc open research.
Expansive soils are responsible for more damage to buildings than any other natural hazard. Geotechnical aspects of buildings on expansive soils in kibaha, tanzania. Yazoo clay belt, especially in the jackson area, is caused primarily by the expansive nature of the clay. Native backfill shall conform to the requirements for class e backfill as defined in the standard specifications for public works. Nearly all types of transportation facilities have been affected by expansive soil behavior and, as. In physical alteration, granular material is mixed with expansive clay to minimize heave. Further details are provided in section d of this manual, and an overview of practices specifically. In the united states, blue clay soil is predominantly found in utahs southern region.