Presentation 2: 20-nov 2020 (Friday) 9:40 am to 10:00 am IST

PVSR Prasad, Keller Ground Engineering India Pvt Ltd

Performance of storage tanks supported by shallow & deep foundations

Storage tanks are heavily loaded thin-shelled structures that exert large loads to large foundations and are generally very sensitive to foundation settlements as it may hinder the performance of tanks resulting in significant commercial or social impacts. Therefore, selection of their foundation is dependent on availability of suitable ground and limitations imposed by design specifications. Design of the tank foundations is generally based on theoretical methods and validation by representative field tests. This paper reviews settlement criteria for storage tanks as per national and international standards, case studies of large to medium diameter tanks supported on deep foundation i.e., bored cast-in-situ piles and shallow foundations on improved ground. Monitoring of tanks supported on different foundations during hydro- tests and product loading is discussed. The paper also presents a study of the viability of these foundation solutions based on the in-situ soil and loading conditions. Paper concludes that storage tanks can also be supported on shallow foundations resting on improved ground reducing the settlement, time and cost significantly depending on the sub-soil. READ BIO

Presentation 3: 20-Nov 2020 (Friday) 10:00 am to 10:20 am IST

Sachin Kamat, ITDCementation

Precast Driven Spun Concrete Pile

It has always been known that driven piles can sustain higher loads in geological conditions where driving was possible. One major hindrance in popularizing precast driven piles has been the need to establish a pile making factory first at site. Casting sufficient numbers of piles, allowing them to gain strength before commencing driving activity meant that the first 3-4 months were lost as a minimum on any project before piles could be installed.

The advent of precast, spun concrete piles in India addresses this issue. Added to this, is the fact that there is significant saving in resources in terms of steel, aggregates, sand etc. Very efficient Hydraulic Impact hammers are now available in India. While experience of commercial  use of Spun Concrete piles in India is about two decades old, there are very few projects where these piles have been utilized. This however should not be a constraint as these piles are very popular amongst many Asian countries and substantial experience of more than six decades exists in these countries. This paper presents an overview of the construction process of Spun Concrete piles and presents two case studies of their use on Industrial projects in Gujarat, India. Spun piles of 400mm and 600 mm diameter were installed as the foundation system. After discussing the constructional aspects, the paper goes on to discuss pile load test results. READ BIO

Presentation 4:  20-Nov 2020 (Friday) 12:20 pm to 12:40 pm IST

Mr Biswanath Dewanjee, Kolkata Metro Rail

Case Study for removal of redundant steel joist piles under base slab of an operational metro station by NATM pilot tunnel for clearing the alignment for East West Metro line tunnels in Kolkata, India

Kolkata East West Metro is a predominantly underground corridor traversing the most congested part of the city. The twin tunnels pass below an existing North-South Metro underground Station at a depth of about 8.6 m from base slab. It was discovered that there was a temporary steel decking for maintaining vehicular traffic during construction of the underground station and parts of some huge redundant steel joist piles were still remaining under the base-slab of existing station which would obstruct the alignment of twin tunnels of new Metro line being bored with EPB tunnel boring machines. Those machines were not capable to cut such steel joists and it was obligatory to remove those joist piles before tunneling. As the steel joist are existing below base slab of an operational metro station, there was no scope for physical extraction of those piles from surface. Proper methodology was devised for removal of those piles by construction of pilot tunnel by New Austrian Tunneling Method [NATM] which was a unique challenge in soft alluvial geology of Kolkata. The pilot tunnel was subsequently suitably filled up for boring of main tunnels. Due to sensitive location of the work, proper measures for minimizing ground settlement was adopted to avert any distress to the structure of the existing metro station as well as metro tracks. Elaborate instrumentation schemes for monitoring ground movement parameters were undertaken during NATM pilot tunnel as well as subsequent work of main tunnels. The geotechnical parameters and design issues associated with this soft ground NATM pilot tunnel and subsequent passage of main tunnels and measures adopted to restrict ground movement are discussed in this case study. The instrumentation schemes for ground movement are also elaborated and the field results are compared with predicted values. READ BIO