GROUTING GROUTING Grouting is a process of ground

GROUTING

GROUTING • • Grouting is a process of ground improvement attained by injecting fluid like material into subsurface soil or rock. • Grouting is the injection specially formulated cement of stable suspensions • or liquid into pores, fissures or voids, or the jetting of cement mixtures at • high flow rate and pressure into the soil to create soil- cement to increase • the strength.

APPLICATIONS • Producing mass concrete structures and piles • Fixing ground anchors for sheet pile walls, concrete pile walls, retaining walls tunnels etc • Repairing a ground underneath a formation or cracks and structural • Defects on building masonry or pavement. • Fixing the tendons in prestressed post tensioned concrete • Filling the void between the lining and rock face in tunnel works

GROUTING MATERIAL TYPES (a) Suspension grouts: These are multi-phase systems capable of forming sub systems after being subjected to natural sieving processes, with chemical properties which must be carefully scrutinized so as to ensure that they do not militate against controlled properties of setting and strength. Water in association with cement, lime, soil, etc. , constitute suspensions. Emulsion (asphalt or bitumen) with water is a two-phase system which is also included under suspension. (b) Solution grouts: These are intimate one-phase system retaining an originally designed chemical balance until completion of the relevant reactions. Solutions in which the solute is present in the colloidal state are known as colloidal solutions. Chemical grouts fall into this category.

MATERIALS USED FOR GROUTING • Cement and water • Cement, rock flour and water • Cement, clay and water • Cement clay, sand water • Asphalt • Clay and water • Chemicals

ADMIXTURES Common admixtures used with cement grouts: 1. Calcium chloride ] 2. Sodium hydroxide ]---------for accelerating setting time 3. Sodium silicate ] 4. Gypsum ] 5. Lime sugar ]-----------for retarding setting time. 6. Sodium tannate ] 7. Fine bentonite ] 8. Clay ] 9. Ground shale ]----for reducing cost of grout and reduces 10. Rock flour ] strength of grout

PERMEATION Grout is injected into the soil at low pressure and fills the voids without significantly changing the soil’s structure and volume. Variety of binders are used with this technique, the choice of which is dictated mainly by the permeability of the soil. When the coefficient of permeability is greater than 10 -2 cm/sec, water-cement mixes are used and for permeability as low as 10 -5 cm/sec, the more expensive resin based grouts are used. Soils with K values lower than 10 -6 cm/sec are normally not groutable by permeation.

COMPACTION PERMEATION The basic concept is of injecting an highly viscous grout with high internal friction, injected into a compactable soil, the grout acts as a radial-hydraulic jack and physically displaces the soil particles thus achieving controlled densification. Advantages 1. Minimum disturbance to the structure and surrounding ground, 2. Minimum risk during construction. 3. Ground water not affected. 4. Supports all portions of structures.

COMPACTION PERMEATION Disadvantages • Grouting adjacent to unsupported slopes may be ineffective. • Not suitable in decomposable materials. • Danger of filling underground pipes with grout. • Effectiveness questionable in saturated clays

MICROFINE CEMENT Thick slurries can not penetrate fine cracks and higher injection pressures would cause fracturing of ground foundations. Because of the higher water requirements of micro fine cement, the slurry remains fluid enough to flow into and penetrate fine sands and small cracks in rock. These cements can treat finer grained sands not possible to treat with Portland cement alone. They are also used to stabilize waste plumes.

CHEMICAL GROUTING A key advantage of chemical grouting is the ability to introduce grout into soil pores without any essential change in the original soil volume and structure, thus changing the support capability of granular soils without disturbing them. Another advantage is the ability to be less disruptive and enable tunneling to proceed without over-excavation. A possible drawback of chemical grouting is that only certain soil types are amenable. Another barrier to the use of chemical grouting techniques in the recent is increasing concern regarding potential pollution by chemical grouting in urban areas. Two trends have addressed this issue: 1. Improvement of grouts through the development of new formulae that enhance the penetrability of particulate suspensions and meet the strictest specifications for environmental safety 2. Development of alternative techniques which by-pass the penetrability restraints, such as jet grouting which allows the treatment of most types of soil, independent of its grain size and permeability, using simple cement grouts

COMPACTION PERMEATION

COMPENSATION GROUTING 1. Compensation (hydrofracture) grouting uses high-mobility grout to split the ground and thereby create lifting or densification under structures or other facilities. 2. The ground is deliberately split by injecting stable fluid cementbased grouts at high pressures in order to increase total stress by the wedging action of successive thin grout lenses, to fill unconnected voids, and possibly to consolidate the soil locally under injection. 3. This process is often undertaken as a reaction to movements while tunnel excavation is in progress. 4. It is important to keep in mind that the effects of compensation (hydrofracture) grouting are difficult to control and the potential danger of damaging adjacent structures by the use of high pressure may prove prohibitive

JET GROUTING 1. It is a technology in which high- pressure jets of cement grout are discharged sideways into the borehole wall to simultaneously excavate and then mix with the soil. 2. The outstanding feature of jet grouting is the ability to treat a whole range of soils, from silty sands to cohesive deposits, by means of simple cement grouts. 3. Jet grouting can be performed in soils with a wide range of granulometries and permeabilites.

ADVANTAGES 1. the ability to use very small drilling tools (90 mm diameter) to create large elements (1. 2 m to 2. 4 m diameter) using pressure and flow; 2. the ability to drill underneath obstacles and solidify zones which are hard to access; 3. the use of technically sophisticated techniques such as highpowered pumps and monitoring devices with continuous measurement of all operational parameters.

JET GROUTING

GROUTING PLANT AND EQUIPMENT A grouting plant includes a mixer, an agitator, a pump, and piping connected to grout holes. Two systems: single line type and circulating type. In the circulation type, the unused grout is returned to the agitator and in the single-line type the grout refused is wasted. The basic items required for a grouting plant and their functions are: (a) Measuring tank-to control the volume of grout injected. (b) Mixer-to mix the grout ingredients (c) Agitator-to keep the solid particles in suspension until pumped (d) Pump-to draw the grout from the agitator to deliver to the pumping line. (e) Control fittings-to control the injection rate and pressure so that the hole can be regularly blend with water and thin grout.

SCHEMATIC REPRESENTATION

PRECAUTIONS The following are the precautions while mixing a grout: • Water is placed first in the mixer. • Mixer is run at the maximum speed before adding the cement. • Grout is mixed in batches. • Ingredients have to be measured in volume • Enough water should be maintained to cover the rotor while it is functioning. • Mixer should not be allowed to run for more than a few minutes between batches. • Mixers should be cleaned thoroughly after the day’s work.

DRILLING INJECTION HOLES Holes for the injection of grout may be drilled with jack hammers, wagon drills or diamond drills, depending on the terrain, class of foundation material, and size and depth of holes. Diamond drills usually give holes of uniform shape, while wagon drills are satisfactory for holes up to about 10 meters depth.

WASHING AND GROUTING THE SEAMS Preparations for washing or grouting seams, consists of installing a section of pipe of about 35 to 50 mm dia and 0. 50 to 1. 0 m long in the grout hole with the top and projecting out a short distance for connection to an air line or a pump. For grouting the seams with neat cement for consolidation purposes it is desirable to deposit the cement in clean seams by removing any clay or any other unwanted materials. For this cleaning effective method is to force a mixture of air and water through the seams. For deciding the pressure for grouting operation, most common practice is to use a pressure 0. 2 kg/cm 2 for each meter of depth of hole.