Underwater concreting and soil reinforcement techniques,
Download as PPSX, PDF14 likes3,790 views
The document discusses the tremie method for concrete placement, which requires maintaining a full pipe of concrete to exclude air and water during the process. It also describes grouted concrete and pre-packed concrete methods, including the use of geotextiles for soil reinforcement and drainage. The advantages of these methods include lower drying shrinkage and enhanced durability compared to conventional concrete.
Underwater concreting and soil reinforcement techniques,
- 5. . • Before concreting air and water must be excluded keeping the pipe full of concrete all the time. • For this the funnel and the pipe should have equal capacity. • Firstly plug is inserted in the pipe with pressure of fresh concrete so that the air is displaced
- 9. The buckets are usually fitted with drop-bottom or bottom-roller gates which open freely outward when tripped. The bucket is fully filled along with concrete and its top covered along with a canvas cloth or a gunny bag to avoid the disturbance of concrete as the bucket is lowered within water.
- 13. PLACING IN BAGS
- 15. In this method, properly concrete filled bags are lowered into water and placed carefully in a header and stretcher fashion as in brick masonry with the help of divers. . A work is slow and laborious, as the accurate positioning of the bags in place can be only accomplished by the divers. The bags and labour necessary to fill and tie them are relatively expensive. This method is only suited for placing the concrete in shallow water.
- 16. In this method, the aggregate should be wetted before placing in position. This method is also called as grouted concrete. It consists of placing the coarse aggregate only in the forms and thoroughly compacting it to form a pre-packed mass.
- 17. In this method, the aggregate should be wetted before placing in position. This method is also called as grouted concrete. It consists of placing the coarse aggregate only in the forms and thoroughly compacting it to form a pre-packed mass. This mass is then grouted with the cement mortar of the required proportions. The mortar that grouts the concrete displaces water and fills the voids. Dense and compact concrete should be prepared by using well graded aggregates The maximum size of aggregate conveniently used is 80 mm. The coarse aggregate may also be allowed to fall from heights of up to 4 m, without causing any appreciable segregation. Just shutter vibrations could be used for compact the coarse aggregate. An air-entraining agent is also added to the mortar to entrain about 4% of air. A small variation of the procedure of preparation of the cement mortar for grouting leads to a process called colcrete. In this procedure, the mortar grout is prepared in a special high-speed mixer. No admixtures are used within this procedure. A mortar consists of fine sand, pozzlanic filler material and as chemical agent that serves the penetration, early setting of cement, and the dispersion of particles and to increase the fluidity of mortar.
- 18. • The grout pressure will be about 0.2 to 0.3 MPa. The quantity of grout should be estimated from the void contents of the coarse aggregates. The pre-packed concrete has lower drying shrinkage and higher durability, especially freezing and thawing resistance compared to ordinary concrete for the same proportions. • (c) Pumping the grout into aggregate mass from bottom at carefully designed positions through a network of pipes. The formwork should be constructed at the top of the coarse aggregate in this method • (b) The grout could be poured on the top surface of aggregate and allowed to penetrate to the bottom. The method is particularly useful for grouting thin sections. • (a) The mould could be filled with grout and the coarse aggregate can be deposited in the grout. METHODS OF PREPACKED CONCRETE
- 20. USING GEOTEXTILES • Geotextiles are fabrics which are used to filter,drain or reinforce the soil. 1.GEOTEXTILES They are made of polypropylene
- 21. MAJOR FUNCTIONS OF GEOTEXTILES
- 22. GEOGRIDS ARE USED FOR WALL CONSTRUCTION DRAINAGE CONSTRUCTION
- 23. 1.GEOGRIIDS ARE PLACED ON THE SUBSOIL. • 2.THEN THE ELEVATIONS ARE MARKED .
- 29. THAN K YOU!