Grouting in Soils

This presentation is related about soil improvement techniques. It includes the basic definitions and types of grouting.

1. PRESENTATION ON GROUTING IN SOIL PRESENTED BY:- SHOAIB BASHIR WANI 18-CE-08 1

2. CONTENTS Introduction History & Development of Grouting Grout & its types Desirable Characteristics of Grout Grouting Methods Permeation Grouting Displacement-Compaction Grouting Displacement-Soil Fracture Grouting Jet or Replacement –Displacement Grouting Rock Fissure Grouting Tube-a-Manchettes(TAM) Grouting Conclusion 2

3. INTRODUCTION Injection of slurry or a liquid solution into a soil or rock formation is termed as grouting. The injected material is referred to as the grout. The process of grouting was developed primarily as a technique for making vertical seepage barriers beneath dams and hydraulic structures by injecting cement slurry into the void space of river bed material. 3

4. History & Development of Grouting Its traceable record can be as early as in the beginning of 1800s. In 1802, the idea of improving the bearing capacity under a sluice by the injection of self-hardening cementitious slurry was first introduced. In 1893, the first systematic grouting of rock in the USA as performed at the New Croton Dam, in New York. In 1960s, jet grouting technique was developed. In 1977, first application of compaction grouting for controlling ground movement during construction of the Bolton Hill Tunnel . 4

5. WHAT IS A GROUT..? Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints (like those between tiles ). Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel. 5

6. Types of Grout Suspension :- Suspensions consist of small-sized particles dispersed in a liquid medium. These include cement grouts, that is, slurry of cement in water; soil-cement grouts consisting of slurry of soil and cement in water; and Bentonite grouts comprising slurry of Bentonite in water. Emulsion :- Emulsions consist of colloidal droplets of liquid dispersed in a liquid medium; bituminous emulsion fall in this category. Solutions:- Solutions are liquid homogenous molecular mixtures of two or more substances; chemical grouts such as sodium silicate solutions and acrylic resins are examples of solutions 6

7. Desirable Characteristics of Grout Properties of a grout are described in terms of five parameters :- Groutability:- Expresses the ability of the grout to reach the desired location in the soil, mass. To be able to do so the grout should possess sufficiently high fluidity and the suspended particles, if any, must be of a size that enables them to enter the void spaces in the soil mass. Groutability Ratio = D 15 of soil / D 85 of grout > 25 Stability:- I s the capacity of the grout to remain in a fluid state and not segregate into its separate components. We need the grout to be stable until it has reached its destination. Stability of clay-cement grout is usually more than that of a cement grout. 7

8. Setting Time:- Is the time it takes before the grout sets into a cemented mass or gel. Early setting can cause difficulty in grout reaching its destination and late setting can result in the grout being washed away if seepage is occurring through the soil. Additives are used to retard or accelerate the setting time as required. Permanence:- Indicates the resistance the grout possess against being displaced from the soil voids with time. Cement grouts have greater permanence than Bentonite grouts which can get washed away with time by seepage of water through the grouted zone. Toxicity:- Is the capacity of the grout to contaminate the ground water coming in contact with it and of adversely affecting the health of workers handling and injecting the grout into the soil. 8

9. Grouting Methods Permeation Grouting Displacement-Compaction Grouting Displacement-Soil Fracture Grouting Jet or Replacement-Displacement Grouting Rock-Fissure grouting Tube-a-Manchettes(TAM) Grouting 9

10. Permeation Grouting:- Permeation Grouting is defined as a means of impregnating the voids within a soil or rock mass and thereby displacing water and air from the voids and replacing it with grout, without displacing the soil particles or widening the existing fissures in the rock. It includes:- Injection of thin grouts into the soil. Once the soil cures, becomes a solid mass. Done usually using chemical grouts. Used for creating groundwater barriers or preparing ground before tunneling. 10

11. Permeation Grouting in Rocks Application of Permeation Grouting:- Permeation grouting is widely used for making vertical seepage barriers beneath hydraulic structures. It is also used for stabilization of soil around tunnels and shafts. Other uses include stoppage of seepage through joints of underground structures such as tunnel lining, basement wall etc.   11

12. core shell Grout curtain Alluvium Fissured rock Sound rock (a) Grout curtain beneath dam   (b) Stabilization of crown of tunnel with chemical grout. 12

13. Conceptual Diagram of Soil Solidification by Permeation Grouting. Grouting Pressure:- To enable rapid permeation of grout slurry into the void space, a high injecting, that is, grouting pressure is desirable. It must not, however, cause the soil mass to displace or to fracture. Hence the grout pressure has to be limited to 25% of the effective overburden pressure at the depth of grouting . 13

14. At point A, the state of vertical effective stress is as follows: Vertical effective stress = ơ / v = Ɣ t h(major principal stress), and for soils in the ‘at rest’ condition, Horizontal effective stress = ơ / h =K O Ɣ t h(minor principal stress)   = 14 Grouting Plant for permeation grouting using cement grout.

15. 15 Displacement-Compaction Grouting:- Compaction grouting is the injection of a thick, low mobility grout that remains in a homogeneous mass without entering soil pores. As the grout mass expands, the surrounding soil is displaced and densified. A conceptual drawing of compaction grouting is shown below:- When low-slump compaction grout is injected into granular soils, grout bulbs are formed that displace and densify the surrounding loose soils. Used to repair structures that have excessive settlement

16. 16 Application of Displacement-Compaction Grouting:- Situations where displacement-compaction grouting is most applicable  

17. 17 Displacement-Soil Fracture Grouting:- Soil fracture grouting technique is a displacement grouting technique in which a learn slurry of cement, soil and water is injected into the soil at high pressure to fracture the soil and form root-like or thin lens shaped zones of grout material in the soil mass. The grout material spreads all around the grout hole causing densification of the soil mass and an increase in its macroscopic strength. Restoration of verticality of a tilted building. Displacement-Soil Fracture Grouting

18. 18 Jet or Replacement-Displacement Grouting:- In this technique, a special grout pipe called the monitor having high-speed jets of water or grout is used to erode and excavate the soil. Thereafter, as the monitor is withdrawn, strong, impervious columns are produced by mixing grout with the remaining soil. Developed in Japan–Uses a special pipe with horizontal jets that inject grout into the ground at high pressures.

19. 19 The sequence followed in jet grouting

20. 20 Application of Jet-Grouting:- Grouted Columns:- Jet grouted columns can be formed in almost all types of soil ranging from sandy gravels to clays. Sands are best suited for treatment yielding the largest diameter of columns. Presence of inter particle attractive forces reduces the erosive efficiency of the jets. Hence diameter of grouted columns are progressively smaller in sandy silts, silts, clayey silts and clay. Gravels do not respond well to jet grouting both because of loss of water or grout through its voids and the difficulty in removing gravel particles.

21. 21 Applications of jet grouting Rock Fissure Grouting:- Rock fissure grouting is the use of a hole drilled through the fissures and joints of a rock mass to allow grout to be injected at close centers vertically and re-injecting, if necessary. Grouting Mechanism There is only one grouting mechanism for rock grouting. The following schematic diagrams show how the mechanism for grouting in rock is. The grout is injected under pressure through the grout hole drilled into the rock mass to be treated.

22. 22 Grouting in Progress Grouting Completed  

23. 23 Application of Rock-Fissure Grouting:- Sealing rock mass underneath and at ends of dams to prevent seepage or leaking of the reservoirs. Sealing rock mass above and underneath a rock tunnel to prevent water seepage into the excavated tunnel. Cementing fractured rock mass. Its main application is in the field of water stopping, especially in tunnel excavation project.

24. 24 Tube-a-Manchettes(TAM) Grouting:- Tube-à-Manchette (TAM) grouting is the use of sleeved perforated pipes in grout holes, soils or completely decomposed rock to allow grout to be injected at close centers vertically, and re-injected, if necessary. Grouting Mechanism:- It is a grouting technique for grouting in soil formation only, with partial or complete displacement of in-filling ground water.   Schematic Diagram of the Impregnation Mechanism for TAM Grouting

25. 25      

26. 26 Applications of Tube-a-Manchettes(TAM) Grouting:- Sealing soil mass above and underneath a tunnel excavated in soil under compressed air condition . Sealing “windows” in cofferdams. Consolidation of loose soil mass (cohesion less granular sand). Sealing underlying soil of dams

27. 27  CONCLUSION Grouting is a popular ground treatment technique, but not so many engineers are familiar with it. And they often have misconception about grouting. The project is to clarify on one hand the basics of grouting, and then on the other hand try to provide a full coverage of all types of grouting mechanisms in practice. For each grouting mechanism, a brief discussion is given to its design considerations, construction and application. Finally, finite element method is used to analyze and model grouting to confirm the extent of grouting in terms of treatment zone and degree of improvement of ground properties required.  

28. 28 THANK YOU