Foundation Practices & Rehabilitation of Structures on Expansive Soils

Rama Subbarao G.V., Associate Professor, Department of Civil Engineering, S.R.K. Institute of Technology, Enikepadu, Vijayawada.

Expansive soils popularly known as Black cotton soils in India are highly problematic, as they swell on absorption of water and shrink on evaporation thereof. Because of this alternate swell and shrinkage, distress is caused to the foundations of structures laid on such soils. Extensive research is going on to find the solutions to black cotton soils. The present paper reviews innovative solutions along with conventional foundation practices to counteract the dual problem of swelling and shrinkage posed by expansive soils. Besides, the present paper throws a light on causes of distress in lightly loaded structures founded on expansive soils and also various measures to rehabilitate the distressed structure founded on them.

Introduction

Expansive soil is commonly known as black cotton soils, because of their color and their suitability for growing cotton. Black cotton soil is one of the major regional soil deposits in India, covering an area of about 3.0 lakh sq.km. Expansive soils are problematic soils because of their inherent potential to undergo volume changes corresponding to changes in the moisture regime. When they imbibe water during monsoon, they expand and on evaporation there of in summer, they shrink. Because of this alternate swelling and shrinkage, structures founded on them are severally damaged. The annul cost of damage to the civil engineering structures is estimated at £150 million in the UK, $1000 million in the USA and many billion of pounds worldwide (Gourley et al. 1993).

In India, black cotton soils have liquid limit values ranging from 50 to 100%, plasticity index ranging from 20 to 65% and shrinkage limit from 9 to 14%. The amount of swell generally increases with increase in the plasticity index. The swelling potential depends on the type of clay mineral, crystal lattice structure, cation exchange capacity, ability of water absorption, density and water content. Swell in the vertical direction is called heave. Among the illite, kaolinite and montmorillinite clay minerals, the montmorillinite possesses the greatest ability to swell by illite. The Kaolinite does not swell. Black cotton soils are very hard in dry state and possess high bearing capacity. In summer, it is very common to see shrinkage cracks with hexagonal columnar structure, with vertical cracks as wide as 10mm extending up to a depth of 3m or more. Soils containing expansive clays become very sticky when wet and usually are characterized by surface cracks or a "popcorn" texture (Fig.1) when dry. Therefore, the presence of surface cracks (Fig.2) is usually an indication of an expansive soil.

NBM&CW June 2011

Repair & Rehabilitation of Concrete Structures - A Paradigm Shift

Repair and rehabilitation of rapidly deteriorating structures is a matter of concern for most countries in the world. Deterioration is observed in the form of cracking and corrosion (Riveros et al., 2018). It is very difficult to Read More ...

Preservation of Capex Towards Industrial Cooling Towers

Industrial Cooling Towers are used to remove heat through evaporation of water in a moving air stream being carried from various sources such as a machinery or some heated process material. Their main use is to remove Read More ...

India's Repair Industry Needs a Responsibility Criteria

In India, the repair industry is not organized, hence, the exact numbers on annual cost to owners/public funding for repair, protection & strengthening are not available. Today, India is placing new concrete to the tune of Read More ...

Rehabilitation of Overstressed Rigid Pavements

Due to shortage of resources like cement as well as finances, hardly any concrete roads were constructed in free India, though, in the long run they are cheaper than bituminous roads, was an established fact. Some internal Read More ...

Concrete Repair: Principles from EN 1504 and Practical Considerations

Many a times, even after taking all the due precautions and all quality control measures, Concrete structures deteriorate. One of the practical reasons is due to the fact, that at the time of planning or at the design table Read More ...

Repair & Rehabilitation to improve life-span of buildings

Across Indian cities, there are millions of old buildings that are in a dilapidated condition. In Mumbai alone, there are 14,375 dilapidated structures across the city and another 10,500 in the suburbs. Such structures pose an Read More ...

Repair/Rehabilitation of Structure

UPV Test in Progress
A structure, when it is constructed, has generally got a service life. The service life is dependent on the quality, workmanship of the construction and various other factors including materials, components, Read More ...

Remedial measures for reinforced concrete structures using cementitious materials

Remedial Measures for Reinforced Concrete Structures
An essential part of a successful repair of concrete structures, is to establish the underlying cause and extent of concrete deficiency, and deterioration mechanism. For a repair to be successfully completed, Read More ...

Latest Techniques for Repair & Rehabilitation- A Perspective

Latest Techniques for Repair Rehabilitation
For a successful repairing work of a structure, the most vital things to be considered are identification of the root cause, selection of the right products & methods, proper repairing of the damage by skilled Read More ...

Durable Repairs State-of-the-art Corrosion Mitigation Techniques

Steel Protected in Carbonated Concrete
Most of today's concrete construction relies on the composite interaction of concrete and steel, which is aided by the near equivalence of their thermal expansion characteristics Read More ...

Concrete Repair: Principles, Guidelines and Practical Considerations

Steps For Repair
India has witnessed a tremendous spurt in construction over the last couple of decades. Residential, Commercial, Industrial and Infrastructure construction and expansion has been progressing Read More ...

Polymers blend for repair applications (Epoxy resins & polymers)

Micrographs of Polymer Blends
Epoxy resins are widely used as highly cross linked materials in various repair applications where special performances such as good mechanical, thermal and electrical properties are required Read More ...

Concrete structures repair & Rehabilitation - Causes of Distress & its Solution

Concrete Degradation
CONCRETE DEGRADATION may have various causes & reasons. It can be damaged by factors like fire, alkali - aggregate reaction expansion, sea water effects, bacterial corrosion, calcium leaching, physical Read More ...

Soil Strengthening – Use of Pressure Injection Grouting as a means of Improving Load Bearing Capacity of Existing Foundations

Ejection of Underground Water
This Paper describes the procedure for improving the Load bearing capacity of the foundations by means of strengthening the soil under and around the foundations. Use of Injection grouting in the Read More ...

Retrofit of R.C. Beams & Columns

Finite Element
During the last week of March a few years ago, author was invited by a certain Company in an Indian city to review and advise upon measures to strengthen the ground floor and basement beams and columns Read More ...

Stainless Steel Rebar: A Necessity for Coastal Regions

Ferritic Stainless Steel
Both stainless steel and carbon steel derive their corrosion resistance from a naturally occurring chromium rich oxide film, which is present on its surface. This invisible film is inert, tightly adherent Read More ...
NBM&CW

New Building Material & Construction World

New Building Material & Construction World
MGS Architecture

Modern Green Structures & Architecture

Modern Green Structures & Architecture
L&ST

Lifting & Specialized Transport

Lifting & Specialized Transport
II&TW

Indian Infrastructure & Tenders Week

Indian Infrastructure & Tenders Week