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VISVESVARAYA TECHNOLOGICAL UNIVERSITY “JNANA SANGAM”, BELAGAVI-590018 TECHNICAL SEMINAR REPORT Submitted in Partial Fulfilment for the award of Degree of Bachelor of Engineering In CIVIL ENGINEERING Submitted by ARADHANA (1BI16CV020) Under the guidance of Mr. GANGADHARA S. (Assistant Professor) Bang...

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VISVESVARAYA TECHNOLOGICAL UNIVERSITY “JNANA SANGAM”, BELAGAVI-590018

TECHNICAL SEMINAR REPORT Submitted in Partial Fulfilment for the award of Degree of

Bachelor of Engineering In

CIVIL ENGINEERING Submitted by

ARADHANA (1BI16CV020)

Under the guidance of

Mr. GANGADHARA S. (Assistant Professor)

Bangalore Institute of Technology K R Road, V V Puram, Bangalore-560004

BANGALORE INSTITUTE OF TECHNOLOGY K.R.Road,V.V.Puram, Bangalore – 560 004

DEPARTMENT OF CIVIL ENGINEERING

CERTIFICATE This is to certify that the TECHNICAL SEMINAR having subject code 15CVS86 is carried out by ARADHNA bearing USN 1BI16CV020, a bonafide student of Bangalore Institute of Technology in partial fulfillment for the award of Bachelor of Engineering Degree in CIVIL ENGINEERING from Visveswaraya Technological University, Belagavi, during academic year 2019 – 2020. It is certified that all suggestions indicated have been incorporated in the report. This Internship Report has been approved as it satisfies the academic requirements in respect of Internship work prescribed for Bachelor of Engineering.

Signature of the Guide

Signature of HOD

Mr. GANGADHARA S.

Dr. H.B.Balakrishna

Assistant Professor

Head of Department

Dept. of Civil Engineering

Dept. of Civil Engineering

Acknowledgement The satisfaction and euphoria that accompany the successful completion of any task would be incomplete without the mention of people who made it possible and under whose constant guidance and encouragement the task was completed. We are indebted to Dr. M. U Aswath, Principal, Bangalore Institute of Technology, Bangalore for his support, cooperation and encouraging remarks. We are grateful to Dr. H.B. Balakrishna, HOD of the Civil Department, BIT Bangalore for his support and encouragement. We extend our sincere appreciation to our guide Mr. Gangadhara S. Assistant Professor, Department of Civil Engineering, Bangalore Institute of Technology who provided his valuable suggestions and precious time in accomplishing my technical seminar work. His guidance gave us the environment to enhance our knowledge, skills and to reach the pinnacle with sheer determination, dedication and hard work. Last but not the least, we express our heartfelt gratitude to Almighty and our friends who gave lot of suggestions to complete the internship work successfully.

ABSTRACT The technical seminar report in board spectrum contains nine chapters in which we tried to give an overview about underwater construction. The content of all section is broadly explained and it is made from the exhaustive study of journals, research papers and other authentic source. In first chapter, I have given a brief introduction about underwater construction, its need in today’s scenario and the materials use for construction. In the second chapter, I have explained in detail the techniques used in underwater construction. This includes mainly caisson and cofferdam whose mechanism of work, types and components are explained. In the third chapter, I have done a specific comparison between the different techniques of underwater construction. In the fourth chapter I have discussed the various loads acting on the caisson and their effect on structure. Fifth chapter of this report has detailed procedure of different methods involved in underwater concreting. Like tremie , pumping, hydro valve method etc. sixth chapter deals with the different underwater concrete properties and how to improve them. It also gives an overview about the type of concrete to be used for underwater construction. Seventh chapter points out the challenges faced during underwater construction and also in the maintenance of such structures. It also underlines some solution for it. In the chapter eigth I have wrote the conclusion of my study on underwater construction and what I learned during this period. Chapter nine contains the references what is used for making this report. After reading all the chapters, one can easily understand basics of underwater construction procedure, its advantages and challenges.

CONTENTS

PAGE NO

CHAPTER 1: INTRODUCTION 1.1 Need Of Underwater Construction

01

1.2 Materials Used For Construction

02

CHAPTER 2: TECHNIQUE OF UNDERWATER CONSTRUCTION 2.1 Cofferdam

04

2.1.1 Cofferdam Types

05

2.1.2 Cofferdam Components

06

2.1.3 Advantages Of Cofferdam

07

2.2 Caisson

08

2.2.1 Types Of Caisson

08

2.2.2 Mechanism Of Caisson

10

2.2.3 Components Of Pneumatic Caisson

10 13

CHAPTER 3: COMPARISON OF CAISSON AND COFFERDM CHAPTER 4: TYPES OF IMPOSED LOAD CHAPTER 5: METHOD OF CONCRETING CHAPTER 6: UNDERWATER CONCRETE

14 16 25

PROPERTIES CHAPTER 7: CHALLANGES CHAPTER 8: CONCLUSION CHAPTER 9: REFERENCES

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1. INTRODUCTION

At the core, underwater construction is simply industrial construction that happens to take place under water. Activities vary greatly but include bridge inspection, building repair, repair of wastewater treatment facilities, and equipment installation.

1.1 Need of underwater construction Population is increasing rapidly with average growth of 1.6% every year. Traffic Congestion is one of the major Problems that India is facing and it has a massive impact on the quality of air, time of travelling, trade and cost. It has been noted that the government are trying their best In order to come up to this problem by creating structures Such as Tunnels, Subways, Flyovers and Bridges. But unfortunately it fails as does not match up with the Increase of population and due to less amount of land available for the construction.

Fig 1.1: Underwater metro tunnel constructed in Kolkata In this report there is a Study on the construction of the buildings and structures with a new technology of constructing under the water. It has been noted that the underwater buildings exist since Year 1960 but no one was aware of it. The underwater Construction

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of the buildings can be advantageous to the People and the environment if proper techniques are used and if people get success in achieving such structures. If Such technology is adapted everything can be built Underwater such as buildings, houses, shopping complex, Museums, entertainment hub, restaurants, hotels, sports Stadiums etc. This can lead to a progressive and a Luxurious life to the people and they can even enjoy their holidays at such places.

Fig 1.2: Ithaa underwater restaurant Encouragement of underwater Building is provided by the glamorous view beneath the Water of fishes, sea beds, different creatures and coral Reefs. This paper discuss about the materials which Should be used for the construction of underwater Buildings, ways of building and special requirements, the possibility of such constructions, advantages and disadvantages of underwater buildings, the impact of Such buildings on environment, effect on the social life and transportation.

1.2 Materials used for construction There are many materials to be had for the building but our Selection should be such that the material fulfils our requirement and to be had with a minimal price. Whilst choosing CIVIL DEPARTMENT, B.I.T

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the materials to be used inside the manufacturing, it is critical to make sure that the burden restriction is not exceeded. The principle fabric used for construction underwater changed into a unique kind of steel and acrylic. The acrylic fabric is used specifically for visibility, on the same time because the steel is used for reinforcements (enables). Excessive energy steel is used as it is in particular Reasonably-priced, and has its immoderate yield electricity. It isn’t always additionally a terrific conductor of power and Warmth. It’s far an excessive corrosion resistance. Acrylic Fabric is used in preference to glass; it is better than glass due To being much less dense, and it's also has higher effect Electricity than the glass. Acrylic gives the herbal duration and colourings of the encompassing materials than glass. It’s Also proper insulator of strength which is good in searching out the fitness and safety of clients and underwater creatures.

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2. TECHNIQUE OF UNDERWATER CONSTRUCTION

As we all know any construction that is laid in water comes under underwater construction, it may be a tunnel, a bridge, dams or some other. As we think of a construction, concrete, foundations, construction technology etc., are some of the aspects that come to our mind. So for underwater constructions, before considering concrete mixtures to be used our main problem is how to lay foundations in water? As digging, laying piles as foundations is a bit difficult task. For this, there are certain methods that are being followed by the engineers of these days. To lay foundations, at first we need to isolate water from the site. This is done by caissons and cofferdams. These caissons and cofferdams can be considered as water retaining boxes or these can also be called as watertight boxes. Once these watertight boxes are built at the construction site in water, these boxes are now dewatered by using suction pipes or some other equipment and that creates some dry space to work on. Later chiselling, drilling and boring are carried out until a hard rock surface is found or reached. And thus foundations are laid as a base for pillars. These boxes are made by using sheet piles that overlock each other to form a watertight box

2.1 Cofferdam A cofferdam, also called a coffer, is an enclosure built within, or in pairs across, a body of water to allow the enclosed area to be pumped out. This pumping creates a dry working environment so that the work can be carried out safely. Enclosed coffers are commonly used for construction or repair of permanent dams, oil platforms, bridge piers, etc., built within or over water. These cofferdams are usually welded steel structures, with components consisting of sheet piles, wales, and cross braces. Such structures are usually dismantled after the

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construction work is completed.

Fig 2.1: Cofferdam

2.1.1 Cofferdam Types Most common cofferdam types are: (1) Single wall cofferdams As the name indicates, single wall cofferdams have only one wall. Typically, single wall cofferdams are built using sheet piles. •Single wall cofferdams can be built quickly with less cost. •Dewatering and constant repairs are needed for single wall cofferdams. •The cost is less for single wall cofferdams. (2) Double wall Double wall cofferdams are somewhat permanent in nature and are built to last for few years. When construction work can take many years, single wall cofferdams may not be suitable. Single wall cofferdams leaks and dewatering is required on a regular basis. This problem can be avoided with a double wall cofferdam. CIVIL DEPARTMENT, B.I.T

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•Double wall cofferdams are costly and need less maintenance. In addition, dewatering inside the work site is negligible. (3) Cellular wall Cellular cofferdams are built when large areas need to be kept dry. Cellular structures can stand-alone and need not be braced. (5) Earth type It is the simplest type of cofferdam. It consists of an earth bank with a clay core or vertical sheet piling enclosing the excavation. It is used for low-level waters with low velocity and easily scoured by water rising over the top. (6) Timber crib Constructed on land and floated into place. Lower portion of each cell is matched with contour of river bed. It uses rock ballast and soil to decrease seepage and sink into place, also known as “Gravity Dam”. It usually consists of 12’x12’ cells and is used in rapid currents or on Rocky River beds. It must be properly designed to resist lateral forces such as tipping / overturning and sliding. (7) Rock fill. These dams are very pervious, to prevent water from seeping an impervious membrane of soil is provided in the dam. The height of the dam is can be up to 3m. The slope can be maintained at 1:1.5 to 1:125. The slope on the water side is pitched so as to protect dam from wave action.

2.1.2 Cofferdam components: • Sheet piling: Sheet piling is a manufactured construction product with a mechanical connection “interlock” at both ends of the section. These mechanical connections interlock with one another to form a continuous wall of sheeting. Sheet pile applications are typically designed to create a rigid barrier for earth and water, while resisting the lateral pressures of those bending forces. The shape or geometry of a section lends to the structural strength. In addition, the soil in which the section is driven has numerous mechanical properties that can affect the performance.

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• Bracing frame • Concrete seal: The typical cofferdam, such as a bridge pier, consists of sheet piles set around a bracing frame and driven into the soil sufficiently far to develop vertical and lateral support and to cut off the flow of soil and, in some cases the flow of water (Fig The structure inside may be founded directly on rock or firm soil or may require pile foundations. In the latter case, these generally extend well below the cofferdam. Inside excavation is usually done using clam shell buckets. In order to dewater the cofferdam, the bottom must be stable and able to resist hydrostatic uplift. Placement of an underwater concrete seal course is the fastest and most common method. An underwater concrete seal course may then be placed prior to dewatering in order to seal off the water, resist its pressure, and also to act as a slab to brace against the inward movement of the sheet piles in order to mobilize their resistance to uplift under the hydrostatic pressure (Fig. 5)

Fig 4 – Typical cofferdam (with seal)

2.1.3 Advantages of Cofferdam Performing work over water has always been more difficult and costly than performing the same work on land. And when the work is performed below water, the difficulties and cost difference can increase geometrically with the depth at which the work is performed. The key to performing marine construction work efficiently is to minimize work over water, and perform as much of the work as possible on land. Below some of the advantages of cofferdams are listed CIVIL DEPARTMENT, B.I.T

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

Allow excavation and construction of structures in otherwise poor environment



Provides safe environment to work



Contractors typically have design responsibility



Steel sheet piles are easily installed and removed



Materials can typically be reused on other projects

2.2 Caisson Caisson is a watertight retaining structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. Caissons are constructed in such a way that the water can be pumped out, keeping the work environment dry.

Fig 5: caisson in china

2.2.1 Types To install a caisson in place, it is brought down through soft mud until a suitable foundation material is encountered. While bedrock is preferred, a stable, hard mud is sometimes used when bedrock is too deep. The four main types of caisson are box caisson, open caisson, pneumatic caisson and monolithic caisson. 1. Box A box caisson is a prefabricated concrete box (with sides and a bottom); it is set down on prepared bases. Once in place, it is filled with concrete to become part of the permanent works, such as the foundation for a bridge pier. Hollow concrete structures are usually

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less dense than water so a box caisson must be ballasted or anchored to keep it from floating until it can be filled with concrete. Sometimes elaborate anchoring systems may be required, such as in tidal zones. Adjustable anchoring systems combined with a GPS survey enable engineers to position a box caisson with pinpoint accuracy. Citation needed 2. Open An open caisson is similar to a box caisson, except that it does not have a bottom face. It is suitable for use in soft clays (e.g. in some river-beds), but not for where there may be large obstructions in the ground. An open caisson that is used in soft grounds or high water tables, where open trench excavations are impractical, can also be used to install deep manholes, pump stations and reception/launch pits for micro tunnelling, pipe jacking and other operations. A caisson is sunk by self-weight, concrete or water ballast placed on top, or by hydraulic jacks. The leading edge (or cutting shoe) of the caisson is sloped out at a sharp angle to aid sinking in a vertical manner; it is usually made of steel. The shoe is generally wider than the caisson to reduce friction, and the leading edge may be supplied with pressurised bentonite slurry, which swells in water, stabilizing settlement by filling depressions and voids. An open caisson may fill with water during sinking. The material is excavated by clamshell excavator bucket on crane. 3. Monolithic A monolithic caisson (or simply a monolith) is larger than the other types of caisson, but similar to open caissons. Such caissons are often found in quay walls, where resistance to impact from ships is required. 4. Pneumatic Shallow caissons may be open to the air, whereas pneumatic caissons (sometimes called pressurized caissons), which penetrate soft mud, are bottomless boxes sealed at the top and filled with compressed air to keep water and mud out at depth. An airlock allows access to the chamber. A pneumatic (compressed-air) caisson has the advantage of providing dry working conditions, which is better for placing concrete. It is also well suited for foundations for which other methods might cause settlement of adjacent structures.

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Construction workers who leave the pressurized environment of the caisson must decompress at a rate that allows symptom-free release of inert gases dissolved in the body tissues if they are to avoid decompression sickness, a condition first identified in caisson workers, and originally named "caisson disease" in recognition of the occupational hazard. Construction of the Brooklyn Bridge, which was built with the help of pressurised caissons, resulted in numerous workers being either killed or permanently injured by caisson disease during its construction. Barotrauma of the ears, sinus cavities and lungs and dysbarism osteonecrosis are other risks.

2.2.2 Mechanism of caisson Caisson is a box but with no floor underneath it. So, when we put it underwater instead of filling up with water as it is airtight, bubbles form. So as a result, we have a dirt floor from where all the water is kept out. But water is heavy so the surface of the water is exerting pressure on the caisson and tries to enter the caisson. So, in order to solve this, we build a platform up in the top and a tube connecting the c...