A SEMINAR On “Recent Advance In Ground Improvement Characterization & Treatment” PREPARED BY SK SOHEL, CE-3RD YEAR GUIDED BY JAYASHREE SENGUPTA ASSISTANT PROFESSOR, CIVIL ENGINEERING DEPARTMENT SUPREME KNOWLEDGE FOUNDATION GROUP OF INSTITUTIONS 1, J.C.Khan Road, Mankundu www.skfgi.edu.in

Definition of Ground Improvement Ground treatment is the controlled alteration of the state, nature or mass behaviour of ground materials in order to achieve an intended satisfactory response to existing or projected environmental and engineering actions.

Main Improvement Techniques: • temporary e.g. dewatering or ground freezing, where the improvement is only during the application • short-term e.g. some forms of grouting, or use of diaphragm walls for ease of construction with longer term benefits • long-term e.g. soil nailing, vibro-replacement, curtain grouting of a dam, where the treatment is integral to the permanent works.

Benefit to the Construction Work Reduction and control of deformation & settlement Reduction, control and exclusion of groundwater to aid safety and buildability Reduction of susceptibility to erosion and improving life-span.

Effect on the Ground • Change of state; i.e. the same ground but made stronger, stiffer, denser, more durable • Change of nature; i.e. the ground becomes a different material by inclusion of other materials Change of response; i.e. through the incorporation of other materials, the ground becomes a composite material with enhanced load-carrying or deformation characteristics.

Main Improvement Techniques: • by vibration • by adding load • by structural reinforcement • by structural fill • by admixtures • by grouting • by specialist dewatering

Benefit Technique ◊◊◊ ◊ Higher Bearing Capacity Less/ more Even ◊◊◊ = Main benefit ◊ = Secondary benefit Benefit Technique Higher Bearing Capacity Less/ more Even settlement Faster Settlement Ground water control Reduced Liquefaction potential Increased Erosion resistance Improved slope / face stability Vibro-replacement ◊◊◊ ◊ Dynamic Compaction Pre compression Vertical Drainage Reinforcing soil / soil nailing Structural fill Lime/cement admixture Permeation grouting Cavity grouting Ground freezing Slurry cut off trench & pumping Well pointing

Vibroflotation Plant Mitchell, J M and Jardine, F M (2002)

Use of Vibration Techniques Mitchell, J M and Jardine, F M (2002)

Vibro-Replacement Principles of column construction using the dry top-feed process 1. Vibrator penetrates weak soils under action of vibrations and ‘compressed air’ jetting medium and forms a hole to design depth, usually a competent bearing stratum 2. After being held at depth for a short time, the vibrator is withdrawn and a charge of stone is placed into the hole 3. The vibrator is reintroduced into the hole, the stone is compacted, forced out and tightly interlocked with the surrounding ground 4. By adding successive charges of stone and compacting each one, a column of very compact stone is built up to ground level Animation Clip Palm Island Dubai

Dynamic Compaction Plant Specialist Rig to reduce noise and environmental disturbance

Dynamic Compaction It involves the repeated dropping of a large weight (15 tonnes or so) from a height of up to 15 metres. The site is usually covered at first with a wide grid, followed by a smaller grid using a lighter weight or a reduced fall. This technique can effectively compact the ground down to a depth of a few metres  Not suitable for small sites or sites where vibration, impact etc can affect adjacent buildings or building service in the ground

Summary – Factors Effecting Ground Improvement Suitability of existing geotechnical materials? Size of improvement area? Availability of specialist plant / equipment? Proximity to existing habitation / buildings? Access & safety considerations? Cost effective: traditional methods?

Activity Examine the following situations and state what ground improvement method would be suitable & why: A deep vertical shaft construction in an area of high ground water. An area of ground with shallow soft man-made fill materials, such as mining waste, for housing development. An area of previously drained and reclaimed silt with low bearing capacity for road construction. The stabilisation of a rock face overhanging a busy railway. A previous land fill tip used for domestic waste. Ground Freezing Dynamic Compaction / vibro-flotation Pre-compression Cement grouting / nailing Importing structural fill

You need to add a few more topics on Ground Freezing Pre-compression Cement grouting / nailing Importing structural fill Also go through the journal attached. Otherwise its ok Add a conclusion at last

Conclusion

Scope of Future Work To best incorporate sustainability considerations in ground improvement method selection and implementation Development of practical, economical and environmentally safe biogeochemical methods for soil stabilization and liquefaction risk mitigation. Development of databases for variability of soil and material parameters required in the design of ground improvement and soil stabilsation. Development of improved and more reliable methods for evaluating the long term durability of soils mixed with binder.

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