Dr. K.M. Soni, Superintending Engineer, CPWD, Bhopal

Black cotton soil, a cohesive soil, is considered a problematic soil for civil engineers. It has characteristics of swelling during rains and shrinking during summer. In both the conditions, it poses problems. During swelling, structure has uplift pressure and produces heave in the foundations, plinth beams, bottom of floors of buildings and canals, roads surfaces etc. and on shrinkage, cracks develop in walls, slabs, plinth protection, floors etc. Though, local construction technology has been developed traditionally in most of the places where such type of soil is found, still cracks are observed in many structures as sufficient precautions are not taken during the construction and maintenance period of the buildings.

Index Properties

Black cotton soil of India has a liquid limit between 60-90%, plastic limit between 30-50% and shrinkage limit about 8-18% as given in Table 1.

Black cotton soils having high plasticity index more than 23 described as critical and severe having free swell more than 100% are to be taken special care to avoid cracks in the structures.

In Situ Properties

Black cotton soil is very hard on drying but becomes slippery and slushy during rains. Its density varies along the depth. On the surface, density is about 1.6 g/cc and reduces to about 1.4 g/cc in dry state along the depth while on saturation, it is almost constant along the depth. When soil is dry, shear strength is quite high on the surface and it reduces marginally along the depth while during rains shear strength reduces and is very low near the surface. Thus, saturated state also has effect on its shear strength. However, properties change up to a certain depth only and then become constant.

Black cotton soil consists of montmorillonite which has swelling characteristics. On its surface and internal layers, it has an electric charge. When the particles come into contact with water, a film is formed around clay particles and the water reaching into layers uplifts the layers and produces heave into the soil. If heave is prevented, say by floorings, it produces uplift pressure. Therefore, to avoid uplift pressure, important consideration is to avoid water coming into contact with black cotton soil.

Remedial Measures to Prevent Damages

Damages to Buildings

Various types of damages can occur in the buildings due to up lift forces and settlement caused by the expansive soils such as:
  1. Diagonal and vertical cracks in smaller direction of slab.

    This section of the article is only available for our subscribers. Please click here to subscribe to a subscription plan to view this part of the article.

Subgrade makes the formation level of the road crust. The material specifications of subgrade material are therefore more demanding than the soil used in general fill or embankment. In some construction projects, it becomes difficult to get the required subgrade

Read more ...

Atasi Das, Assistant Vice President, G R Infraprojects, explains the concept of the Perpetual Pavement in India’s expressway constructions and its practical implementation with due consideration of layers, materials, and thicknesses

Read more ...

Dr. Rakesh Kumar, Senior Principal Scientist & Pankaj Goel, Senior Technical Officer, Rigid Pavements Division,CSIR-Central Road Research Institute (CRRI), New Delhi, give information on the Performance of Curing Compounds in Strengthening

Read more ...

The construction and maintenance of roads with flexible pavements in very cold regions where annual temperatures range between +30oC to -35oC has got its own challenges. The bitumen in the asphalt layer becomes hard at such low temperatures

Read more ...

The Bundelkhand site team achieved yet another feat on 15 Jan 2022 by completing 13 deck slabs of varying types in just 46 days. Therefore, it is a demonstration of exemplary display of overall project executing capabilities

Read more ...

Er. Devjyoti Paul, Project Manager & Er. Harpreet Singh, Chief Project Manager, B&SEC, share the technical and construction features of three bowstring girder ROBs, recently constructed under Package I & III of Purvanchal Expressway in the state of Uttar Pradesh

Read more ...

Use of Extruded Polystyrene Sheets (XPS) in the construction of the Zojila Approach Road has been especially effective as XPS is the most suitable, convenient, and cheaper solution for mitigating frost action on pavements, increasing the life of pavements

Read more ...

The Indian road network is the second largest globally, with a length of around 63.86 lakh km. The outbreak of the virus towards end-FY20 had created panic globally, leading to the temporary suspension of economic activity

Read more ...

Roads and Railways boost awards; tenders up marginally Overall tendering grew 5% YoY during H1FY22 Awarding activity grew at a 2-year CAGR of 22% in H1FY22 Infrastructure credit near all-time highs

Read more ...

There are many challenges being faced by the highway sector such as ensuring availability of construction materials and machinery, timely completion of projects, availability of trained human resources

Read more ...

Practical Recommendations for Construction of Longitudinal Joints in Hot Mix Asphalt (HMA) Pavements Rajib B. Mallick, Ralph White Family Distinguished Professor, Civil and Environmental Engineering, Worcester Polytechnic Institute (WPI), Massachusetts, USA, and Veeraragavan

Read more ...

Plant and Equipment Determine Quality of Road Construction Road Infrastructure projects are time constrained; early completion of project entitles rewards while delays attract penalties. The plants and equipment being used determines the quality of the road

Read more ...

Designing roads and highways efficiently with the right materials will help achieve optimum construction cost, lower maintenance, and reduce life cycle costs. Ash from coal-fired thermal power

Read more ...

Rodic Consultants has emerged as a leader in the infrastructure consulting space with state-of-the-art engineering solutions, and a proven track record of timely completion of projects across sectors

Read more ...

Readymade Kandhal Pothole Patching Mix was adopted as Indian Roads Congress (IRC) Standard Specification IRC: 116-2014 for Readymade Bituminous Pothole Patching Mix Using Cut-Back Bitumen. All concerned

Read more ...

The Bundelkhand Expressway is a 296-km long, 4-lane wide (expandable to 6 lanes) access-controlled expressway in the state of Uttar Pradesh. It will connect Gonda village in Chitrakoot district with Agra–Lucknow

Read more ...

This case study briefly discusses the planning, design and construction of Package 3 of the Purvanchal Expressway. Package-3 of the Purvanchal Expressway is a 41.7km long section of the 340.82km long

Read more ...

Since the 1980’s billions of dollars have been invested in developing methods to make pavement design and construction more sustainable through the re-use of existing resources. This includes insitu recycling and

Read more ...

India has the second largest road network in the world, spanning a total of 5.89 million km, transporting 64.5% of all goods in the country. Nearly 90% of India's total passenger traffic uses the road network to commute

Read more ...

India generates nearly 26,000 tonnes of plastic waste every day, making it the 15th biggest plastic polluter globally. Discarded plastic waste litter the country’s roads, rivers and also form huge mounds in garbage

Read more ...

×
Sign-up for Free Subscription
'India Construction Week'
Weekly e-Newsletter on Construction Industry
Get the latest news, product launches, projects announced / awarded, government policies, investments, and expert views.