Abstract

Construction in the coastal areas includes construction of oil and gas industries in off shore areas which is one of the most crucial challenges as it deals with the exploration and production of flammable things. The construction also includes ports and harbours, and other special marine structures. There are various challenges like unduly waves, unexpected sea storms which can affect the strength of marine structures. The studies reveal that corrosion rates in case of old reinforcement steel bars are very high as compared to fresh reinforcement steel bars, which are used as reinforcements in concrete structures. Therefore, it confirms that reinforcing bars should not be allowed to corrode due to prolonged storage in open space prior to embedment in concrete. In marine construction, the effective cover of 25mm has higher corrosion compare to the effective cover of 50-70 mm.

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Marine clay is type of clay which is found in the coastal regions around the world, It is sometimes called as the quick clay which is notorious for being involved in the landslides, clay particles can self-assemble into various configurations, each with totally different properties, when clay is deposited in the ocean, the presence of excess ions in sea water causes a loose, open structure of the clay particles to form, this process is well known as flocculation. Once stranded and dried by ancient changing ocean levels this open framework means that, such clay is open to water infiltration.

Swelling of marine clay has the potential to destroy building foundations only in few years, due to the changes in the climatic conditions in the construction site, the pavement constructed on the marine clay will have less durability and requires a lot maintenance cost, thus challenging the civil engineering fraternity to find newer long-lasting solutions for the marine site construction problems.

 

1.0  Introduction:

Petroleum which supports daily life on earth could be found on land and beneath ocean. There are two types of locations of explorations and production of oil and gas on shore and off shore, on shore refers to a location on land where the petroleum is found and then explored. When the petroleum is found on sea, the location is an offshore area, offshore areas are situated on sea where the depth could reach more than 2000 meters. Deep marine construction industry has a significant difference compare to normal construction industry

 Severe working condition on offshore construction and operation brings the safety issue becomes paramount topic on all parts of the world where this industry is situated. Denton (1991) stated that the offshore industry presents a very unusual combination of problem from the safety point of view. They include:

·         High pressure systems up to 300 bar and sometimes to 500 bars;

·         A high (300 tons) inventory of explosive and flammable material;

·          Extensive electrical system, often at voltages as high as 6.6 kv;

·           Large scale machinery such as gas turbines, compressors and pumps;

·           All plant placed in a very confined space;

·           Living quarters necessarily very close to working plant;

·           Evacuation of personnel difficult if not impractical in the most adverse weather conditions;

·          Installations all individually designed to meet specific requirements;

·           Installation life of 20 to 30 years;

·          Installation necessarily modified during their life, for example to meet changes in field behaviour.

2.0  Costal Engineering:

We should work with natural environment rather than working against it, this should be our primary objective for working in the costal or marine areas. The structures are founded on the sea bed are exposed to the water level changes along the sea bed or shoreline, sea currents and wave impacts. Further, the site and the area around the structures are, in many cases, subject to morphological changes which have to be analysed and properly understood before the construction process.

It is, therefore, natural for us to try and minimise the use of man-made structures on a shoreline and attempt to use beach nourishment wherever possible. when working on marine projects, seek solutions attempting to minimise human intervention, i.e. placing a port or similar installation where it requires the least movement of materials, by, for example, selecting the site and distance from the shoreline such that the quantities in breakwaters and other structures as well as dredging and filling volumes are minimised. Further, it is our aim to seek solutions that involve the smallest possible changes in the natural, physical as well as flora and fauna environment.

3.0 Overview of India’s marine sector:

India has a long coastline of more than 7500 km. Its marine resources are spread over in the Indian Ocean, Arabian Sea, and Bay of Bengal. The exclusive economic zone (EEZ) of the country has an area of 2.02 million sq. km comprising 0.86 million sq km on the west coast, 0.56 million sq. km on the east coast and 0.6 million sq km around the Andaman and Nicobar Islands. The east coast supports activities such as agriculture and aquaculture while a number of industries are supported on the west coast. Tourism has emerged as a major economic activity in coastal states such as Goa, Kerala and Orissa.

With India building enormous infrastructure along its 7,500-km-long coastline, the need is to make this infrastructure resilient to climate change impacts. But there seems to be no money for this purpose, nor is sufficient attention being paid to the enormous problem.

In October 2014, when Cyclone Hudhud hit the coast of Andhra Pradesh near the city of Vishakhapatnam, the impact was immense. While the decades of development that had gone into the Indian cyclone warning system ensured that the death toll was minimal, the loss to infrastructure was high.

4.0 No money for climate resilient infrastructure:

Planning for climate resilience would need to start from the time of locating the infrastructure facilities. For instance, infrastructure for solid waste management, especially landfills, have to be located keeping in mind the projected sea level rise. Similarly, planning for climate resilience would mean ensuring water supply channels have back-ups for extreme weather events. It is a good time to introduce climate resilience considerations while retiring old infrastructure and replacing with new ones.

Building climate resilience also requires buy-in from the political representatives, since it requires coordination among multiple stakeholders. Elected representatives, such as mayors and municipal commissioners, have the authority to ensure this coordination.

Policies that have a combination of incentives and disincentives will be needed to promote renewable energy. Energy efficiency standards, tax incentives, financing mechanisms, and funding for research and development can have long-term positive impacts.

5.0 Ill-planned development highlights risk:

The actual sea level rise would also be highlighted by the fact that the natural coastline would be disturbed by increased activities. Destruction of coastal sand dunes, cutting down mangroves, dredging coastal mudflats, or building a bund across a coastal wetland would all worsen the local adverse impact of sea level rise. India’s coastal infrastructure development plans include many examples of such ill-planned development.

At any rate, with cyclones and floods forecast to become more frequent and more severe, infrastructure would need to more robust in construction and design, and also be able to spring back into action with minimum downtime.

With more power plants, refineries, captive ports, special economic zones, tourism complexes and highways planned there will certainly be growth of urban centres along India’s coastline, and more migration to these areas. Everything points to the urgent need to build climate resilience into the new and existing infrastructure.

6.0 Legal and policy frameworks are not adequately implemented:

Although a number of laws have been enacted and rules and regulations promulgated for the management and protection of coastal and marine environment, their enforcement has been ineffective, and in many cases laws are partial or incomplete. Legal frameworks remain, for the most part, based on command and control measures which are costly and difficult to enforce given the limited institutional capacity and budget constraints. Economic instruments are used more in support of development ignoring conservation objectives. Adequate funds and effective financing mechanisms are lacking, both for the public agencies who are mandated with development and conservation in coastal and marine zones, as well as for the resource users and local communities who bear many of the indirect costs of maintaining a healthy environment. As a result, there are few concrete incentives for local communities, resource users and land managers to promote sustainable and integrated development and conservation in coastal and marine areas.

7.0 Lack of adequate capacity, skill and knowledge in managing coastal zones:

The organizations and institutions responsible for managing coastal and marine areas do not have adequate capacity to address issues of marine and coastal conservation, sustainable livelihoods, economic development and disaster management in a holistic manner. Most coastal zone planners, environment agencies, and the managers in the sectors whose activities have an impact on the coastal and marine environment have little understanding of these impacts created, or of the possible benefits of coordinated joint actions. There is an insufficient knowledge base in the country to understand and manage direct, indirect and cumulative impacts on the environment, and few if any mechanisms for sharing information on national and international best practice. This is exacerbated by the scarcity of technical and scientific data on the geomorphology, biophysical or socio-economic situations and changes along the coasts.

8.0 Other coastal and marine resources:

Nearly 45 percent of India’s total energy needs are supplied by oil (mostly imported) and gas. Most of the country’s oil and gas reserves lie in the coastal and shallow offshore areas of the Gulf of Kachchh, Bombay High, and Krishna-Godavari Basin, and some in the known deep-sea locations. There is no dependable estimate of ocean energy potential (wave, tidal, ocean thermal energy). Some work has started on coasts where the tidal amplitude is very high (Gulf of Khambhat, Gulf of Kachchh, Hooghly Estuary). Nonetheless, the potential, subject to development of the required technology, is anticipated to be very high.

9.0 Types of material used in aggressive marine environment:

During the past few decades deterioration of concrete in service, especially in marine and other aggressive environments has been attracting the attention of researchers the world over.

The problem of concrete deterioration has been studied by many in the past. As early as 1840, Smeaton and Vicat discussed the problem of concrete in the sea water. A survey of the concrete docks in several European Harbors was undertaken at the beginning of this century. A survey on the durability of reinforced concrete in buildings was conducted in U.K in 1954 and the common defects found in reinforced concrete works were- faulty design, inappropriate choice of materials, faulty construction and severe exposure conditions.

Presently, there is a worldwide concern about the deterioration of concrete and corrosion of reinforcing steel in concrete. In India, the Mandavi Bridge in Goa and Thane Creek Bridge near Bombay are the recent examples of failure due to corrosion of reinforcement in concrete. An understanding of the deterioration of concrete is made difficult due to large number of factors involved like material parameters, production and placement and particularly the environment in which it is supposed to perform. A complete understanding of all the different parameters and their effect on the deterioration of concrete is too much to attempt. However, it is to be noted that the behavior of different concretes in specific environments has to be investigated so that useful guidelines can be set for a better utilization of the scarce raw materials.

            As the magnitude of durability and corrosion problems increased over the years, due to increased industrialization and consequent requirements that material should perform in more and more severe environmental conditions, several types of cement and concretes have been developed to suite individual applications. These vary form conventional plain concrete to the special polymer concrete composites. It is generally accepted that a dense well-made concrete suffers lesser damage even in aggressive environments. Durability of concrete is largely influenced by its physical properties like density, porosity and the quality of constituent materials apart form the nature of deteriorating influences. Various constituents, materials and construction methods play an important role in durability. Hence, the materials chosen should be such that they are durable, over the entire life period of the structures. Structures that are designed to last about 50-100 years sometimes deteriorate in less than 10 years mainly due to corrosion.

Mainly cement contents, maximum water-cement ratio and minimum cover to reinforcing steel have been found to be controlling factors affecting durability of concrete in severe environmental conditions. Among the above factors, the importance of the concrete cover over steel can be realized from the fact that the major factors which lead to severity of the corrosion in reinforced concrete construction are- deterioration of the concrete cover and diffusion of corrosive medium in cracks of concrete cover up to the reinforcement.

The types of cement used for the study of performance of concrete and reinforced concrete materials in aggressive environments are- Ordinary Portland Cement(OPC), Portland Pozzolana Cement (PPC), Sulphate Resisting Cement (SRC), Portland Blast Furnace Slag Cement (PBFSC),

10.0 Comparison of Performance of Different Cements in aggressive environment:

            The relative resistance to sulphates and sea-water, for concretes made form different types of cement available, was studied over a period of one year in Jordan. The cements included a PPC, with 15% natural Pozzolana addition, two ordinary Portland cements and a sulphate resisting Portland cement. The test methods involved storing cubic, briquette and prismatic mortar specimens in the Dead sea and Red sea water, in Na2SO4 and MgSO4 solutions and studying their deterioration through visual observations and relative strength determinations. The condition of the specimen was denoted by “Visual Deterioration Index”, a number ranging form 10 for a geometrically perfect specimen to zero for a completely destroyed specimen.

            In Dead sea, pozzolanic cements performed better followed in decreasing order by ordinary Portland cement and sulphate resisting cement.

            In Red sea, the performance of 3 types of pozzolanic cements varied from best to worst while the performance of OPC and SRC was found to be in the middle.

            In case of sodium sulphate attack (10% concentration) SRC was seen to be the best in performance followed in decreasing order by pozzolanic cements and OPC.

            In the case of MgSO4 attack (14% concentration), SRC again was seen to be best followed by OPC and pozzolanic cements in decreasing order. However, 10% and 14% sulphate concentrations appear to be very high and may cause distorted deterioration which may not be realistic.

            Following table compares the compressive strength of different types of cement after the field exposure of 15 months.

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