GROUND IMPROVEMENT TECHNIQUES TATYASAHEB KORE INSTITUTE OF ENGINEERING AND TECHNOLOGY, WARANANAGAR GROUND IMPROVEMENT TECHNIQUES By 1)Sourabh D. Patil. 2)Ganga H. Tepugade.

Introduction General practice is to use shallow foundations for the foundation of structures if the soil close to the ground surface possesses sufficient bearing capacity. However, where the top soil is either loose or soft, the load from the superstructure has to be transferred to deeper firm strata. In such cases, pile or pier foundations are obvious choice. There is also a third method which may in some cases prove more economical than deep foundation or where the alternate method may become inevitable due to certain site and other environmental condition. This third method comes under the heading soil improvement. Soil improvement is frequently termed soil stabilization, which in its broadest sense is alteration of any property of a soil to improve its engineering performance.

Basic Concept The behavior of a structure depends upon the properties of the soil materials on which the structure rests. Soil improvement : Increases shear strength. Reduces permeability. Reduces compressibility.`

METHODS OF SOIL IMPROVEMENT Mechanical compaction Dynamic compaction Vibroflotation Preloading Sand & stone columns Use of admixtures Injection of suitable grouts Use of geotextile

Compaction CLAY CLAY SAND

Definition Process of compaction The densification of soil by applying mechanical energy is known as compaction. Process of compaction Three Phase Diagram

Methods Of compaction Rolling Ramming Tamping

Benefits It is method which is used to improve soil conditions on large scale; like road construction. When available funds are less & labour available are more then compaction by mechanical means is obvious choice.

GEOTEXTILE GEOTEXTILE

Infrastructure is the basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function. The textile material has the basic property to develop shear-stress when subjected to load. Concrete commonly used in civil to engineering application, to develop and absorb compression stresses and shear stresses. In conventional concrete structure the civil engineers use steel for reinforcement or for absorbing shear stresses. Now this job can be best done by geo-textile because of their fundamental property of developing shear-stress when subjected to load. INTRODUCTION INTRODUCTION

TYPES OF GEOTEXTILE The different types of Geo-Textiles are as follows: Woven geo-textiles: - The concrete bases used for coastal works, water ways, and embankments and in forming grovel for road.

2. Nonwoven geo-textiles:- It is used for Filtration, drainage, reinforcement between soil stone or aggregate and in roads, railways works, erosion prevention and separation.

3. Knitted geo-textiles:- The Knitted bags for protection of dam's riverbank etc. It is also used with foundations, soil, rock, earth or any other related material as an integral part of human man made project, structure or system.

RAW MATERIAL OF GEOTEXTILE:-

Separation: - Separation of two layers of soil with different soil physical properties, such as road gravel from soft sub-base materials. Granular fill- Soft Soil system without Geosynthetic Granular fill- Soft Soil system without Geosynthetic

Reinforcement Function By providing lateral restraint throught interfacial friction between geotextile & soil. Reinforcement Function By providing lateral restraint throught interfacial friction between geotextile & soil

Filtration Function Filtration:- Retaining fine particles when water passes from a fine-grained to a coarse grained layer, such as when water flows from a sandy soil into a geotextile wrapped gravel drain. Filtration Function

Drainage: - The function of drainage is to gather water, which is not required functionally by the structure, such as rainwater or surplus water in the soil, and discharge it. Drainage Function

Prevention of Aggregate Penetration-Separation Applications: Road Construction:- Construction of road on soft soil normally encounters the problems like construction of embankment, uniformly strong pavement and a good riding surface. Lateral or vertical movement of the pavement at the cracks due to load or thermal effects causes the cracks from the existing pavement to propagate up through the new AC overlay (called reflective cracking). GEOTEXTILE Prevention of Aggregate Penetration-Separation

Benefit:- 1) Reduces the excavation depth of unsuitable sub grade. 2) Reduces aggregate thickness required to stabilize the sub grade. 3) Maintains a more uniform settlement of the sub grade especially in transition areas. 4) Improve sub grade strength and extend the life of the system.

Coastal Protection- Erosion Control Due to Sea or River current, fine soils of the bank start migrating causing Erosion Conventional design of cementing the banks is not a solution due to Hydraulic pressure of the soil Geotextile allows water to pass through but resist the fine soil migration

Shankarpur to Halda, West Bengal Installation – Geotextile Tube Geotextile Bags Geotextile Tube

After Installation - During High Tide

Conclusions The behavior of a structure depends upon the properties of the soil materials on which the structure rests. Soil improvement : Increases shear strength. Reduces permeability. Reduces compressibility. Geotextiles play an important role in Separation, Filtration and drainage. In Recent years, High strength Geotextiles and Composites are also used as Reinforcements.

References: 1. http://en.wikipedia.org/wiki 1. http://en.wikipedia.org/wiki   2. Textbook of “Basic and Applied Soil Mechanics” by Gopal Ranjan & A.S.R. Rao (New Age International Publication”) 3. Venkatarama Reddy, B. V., Studies on static soil compaction and compacted soil–cement blocks for walls, Ph D thesis, Dept of Civil Engineering, Indian Institute of Science, Bangalore, India, 1991. 4. Textbook of “Soil Mechanics and Foundation Engineering” by V.N.S. Murthy.

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