CASE STUDY FOR GROUND IMPROVEMENT USING PVD

Khem chand Gurjar2013CE10351

Introduction

• To develop a new port at Gangavaram located

at about 15 kms south of Visakhapatnam Port, AP.

• Back up facilities for coal and iron ore storage and stacking and handling facilities.

Site Description

Port facilities • Coal storage– 12m high

• Iron ore storage– 10m high

Soil Profile

• As a part of the project, 8 Nos boreholes were taken to ascertain the design parameters.– Dredged Sand (0.2-0.3m thick)– Marine Clay with Shells (1-3m thick)– Soft Marine Clay (7-15m thick)

• The safe bearing capacity of the existing soil was worked out as 3 T/m² which was very low to take the loads.

PVD Design• Depth : 10m to 18m• Spacing : (Triangular pattern)– 1m c/c in below the stack – 1.5m c/c in in other area

Consolidation period For 1.5 m spacing : 174daysFor 1m spacing : 65 days

Sand mat 300 mm thickHorizontal Drainage System

Geotextile and band drains laid horizontally connecting these pipes

Post Treatment Assessment

• The instruments as Piezometers, Settlement Recorders, Inclinometers were installed to assess the post treatment performance of the adopted method of treatment.

• The readings were taken every 4 days when loading started, continued for a month after final preload height is achieved. The frequency was later extended to 7 days.

Pore water pressure

1 m c/c : 55-65%1.5 m c/c : 30-40%

Settlement

Settlement with time

Analysis

To determine the ultimate settlement they used two method– Asaoka Method:– Hyperbolic method:

Asaoka Method

Conclusion• With the application of the load the pore pressure

increased and dropped down slowly with time. The pore pressure variation indicated about 55–60% dissipation.

• The Degree of consolidation based on Asaoka Method was evaluated as 78–115% whereas based on Hyperbolic method it was evaluated as 32–70%.

• Hyperbolic Method is more comparable with the Pore Pressure Dissipation Results. Further the results obtained with theoretical slope of hyperbola as 1.00 are more closer to the predicted by pore water pressure analysis.

Reference

Case study for ground improvement using PVD with preloading for coal & iron ore stackyard

• Pallavi Bhosle, Sohams Foundation Engg. Pvt. Ltd., Navi Mumbai–400614, India.E-mail: pallavi@sohams.com

• V.V. Vaishampayan,MD, Sohams Foundation Engg. Pvt. Ltd., Navi Mumbai–400614, India.E-mail: sohams@vsnl.com

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