Under Water Concreting

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SUB STRUCTURE CONSTRUCTIONQ.3 .- what are the methods for under water concreting ? And give the explanation for each method.ANS:Types of underwater concreting Tremie Pump method Toggle bags Bag work1. Tremie method: A tremie is watertight pipe Generally 250mm in dia. Funnel shaped hopper as its upper end and a loose plug at the bottom. Its supported on aworking plate form above the water level.

1. Pump method: Aconcrete pumpis a machine used for transferring liquidconcretebypumping. There are two types of concrete pumps. The first type of concrete pump is attached to atruck. It is known as a trailer-mounted boom concrete pump because it uses aremote-controlledarticulatingroboticarm (called aboom) to place concrete accurately. Boom pumps are used on most of the larger construction projects as they are capable of pumping at very highvolumesand because of the labour saving nature of the placing boom. They are a revolutionary alternative to truck-mounted concrete pumps. The second main type of concrete pump is either mounted on a truck and known as a truck-mounted concrete pump or placed on atrailer, and it is commonly referred to as aline pumpor trailer-mounted concrete pump. This pump requiressteelorflexibleconcrete placinghosesto be manually attached to the outlet of the machine. Those hoses are linked together and lead to wherever the concrete needs to be placed. Line pumps normally pump concrete at lower volumes than boom pumps and are used for smaller volume concrete placing applications such asswimming pools,sidewalks, and single family home concrete slabs and most ground slabs.3. Toggle bags: Toggle bags are ideal for small amount of concrete placement They are bag is filled in a dry with wet concrete Used for repair work The concrete is squeezed out by diver.4. Bag work: Bags are made of open weave material. Diver handled bags are usually of 10 to 20 litres capacity but m3 bags can be placed using the crane.Q.4.-write short note on under water construction of diaphragm wall and basement. ANSDIAPHRAGM WALL

Diaphragm Wall is generally reinforced concrete wall constructed in the ground using under slurry technique which was developed in Europe.

The technique involves excavating a narrow trench that is kept full of an engineered fluid of slurry.

Walls of thickness between 300 and 1200 mm can be formed in this way up to depths of 45 meters.

About Diaphragm wall:

Limited construction time where deeper than normal cantilever support may be required. Can be installed to considerable depth. Formation of walls with substantial thickness. Flexible system in plan layout Easily incorporated into Permanent works. Designable to carry vertical loads. Construction time of Basement can be lowered considerably. Economic and Positive solution for large deep basement in saturated and unstable soil profiles.

Construction Procedure of Diaphragm wall:

Stage-1:Fixing of AlignmentStage-2:Guide wall ConstructionStage-3:TrenchingStage-4:Trench CleaningStage-5:Stop ends fixingStage-6:Reinforcement Cage loweringStage-7:Placing of ConcreteStage-8:Withdrawal of Stop ends


BASEMENT Abasementorcellaris one or morefloorsof a building that are either completely or partially below theground floor. Basements are typically used as a utility space for a building where such items as theboiler,water heater,breaker panelorfuse box,car park, andair-conditioning systemare located; so also are amenities such as the electrical distribution system, andcable televisiondistribution point. However in cities with high property prices such asLondon, basements are often fitted out to a high standard and used as living space.

Q 5.- Explain tunnelling technology with respect of advance planning and equipment.ANS Technical aspect of construction methods and equipment along with tunnel characteristics from the basis of tunnel design. A properly design tunnel takes consideration both construction and end use and thus,by adjusting one to the other maximum over economy can be attained,also from the tunnel characteristic and as shape diameter and soil condition the tunnel technic are establish. Depending of end use of tunnel,the tunnel shape and diameter can be decided.for example tunnel is used for vehicular,rail or foot transport,then horse shoes of the tunnel are the best suited and these can be constructed efficiently with the help of model tunnelling equipment . Finished diameter or size of the tunnel is based on required capacity of the end use generally the cost of smaller tunnels can be reduced by slightly increasing the site toallow enough room for machinery and men to work with case. Another aspect to be study in technical planning is tunnel gradient. This will depend on the surface terrain and on the use of the tunnel. If the grade is steep,for example addition horse power in the power unit of haulage system will be needed for breaking and accelerating. Aflat grade, on the other hand will hamper the flow of ground water which is prevalent in most tunnel.

Tunnel equipment:1. Roadheaders2. Tunnel Boring Machines3. Transportation & Haulage4. Infrastructure & Surface Plant Road headers:

ROADHEADERSUses and refurbished: MEKTUNNEL are your Roadheader experts. We manage one of the largest inventories of available used Roadheader inventories globally and can offer quality used and refurbished Roadheaders of all brands and models to satisfy your project and budgetary requirements.New road houlders: MEKTUNNEL proudly representsBBM MaschinenfabrikMeran GmbH. BBM produces a full range of top quality German build Roadheaders and provides excellent support and expertise to assist you in making sure your project is a success. The BBM brand of Roadheaders was previously sold under the Westfalia. Roadheader brand and they are world renowned for quality and reliability.Compact Roadheading and Cross Passage Solutions: MEKTUNNEL can supply compact continuous mining/excavation solutions in the