Date : 11/26/2014

Research Division: Buildings, Bridges and Embankments

Research Project Topic:

“Practical Analysis for Stone Columns in Soft Clays under Central Vertical Loading”

1- Statement of the Problem:
As the world’s population continues to grow, there is an increasing need to construct on marginal or inadequate soils. Traditionally, deep foundation methods such as piles and drilled concrete shafts have been used to transfer loads either deeper within these marginal or inadequate soils or to better materials below them. Recently, there has been a trend toward improving the load-carrying capacity of these soils using reinforcement, modification, or stabilization techniques. Stone columns are one of these soil improvement methods that are ideally suited for improving soft silts and clays and loose silty sands and offer a valuable technique under suitable conditions for (1) increasing bearing capacity, (2) reducing settlements, and (3) increasing the time rate of settlement.
2- Scope and Objective of Study:
The actual stone column behavior involves the load transfer due to different material stiffness. The surrounding soil properties, in fact, are totally changed due to the way of construction. Thus, the different ways of construction and their effects on the surrounding soil and stone columns will be studied first. Then, a theoretical analysis will be done for a single stone column considering the constructions’ effects. The theoretical solution should be assessed using some field measurements and geotechnical Finite Element (FE).
As a result, the stone columns in group should be affected by the construction method. Hence, a study on the stone columns as a group in embankment, isolated footing, and raft will be conducted using geotechnical FE software. Finally, a comparison between using piles and stone columns as solutions for soft clays will be conducted using some case studies for structures.
3- Research Plan:
(1) To present an up-to-date state of the art and literature review on the stone column concept as a soil improvement technique with the recent references.
(2) Study of different ways for stone columns’ construction and their effects on the surrounding soils’ and the stone columns’ properties, as well as the soil consolidation.
(3) Theoretical study of a single stone column in soft clay considering the construction’s effects.
(4) Assessment of the theoretical solution using field measurements and FE analyses.
(5) FE analyses of stone columns in group considering the construction’s effects for an/a:
a. Embankments.
b. Isolated Footings; Rectangular, Square, Strip, Combined and Strap.
c. Rafts.
(6) Stone columns’ solution vs. Piles’ solution for some structures in soft clays.
Dr. Hany Farouk Shehata