L&T GeoStructure Leading by Experience
T. Srinivasan, Head & CEO, L&T GeoStructure, a leading geotechnical specialist contractor, discusses the challenges in construction of deep foundations in India, the lack of awareness of the importance of geotechnical investigations, the dearth of skilled workers in this field, and the solutions being offered by the company.
How is the civil construction industry evolving with respect to cutting-edge technologies and expertise in civil construction?
India is growing at a remarkable phase, thanks to the various projects undertaken by the Government and private players in developing infrastructure from rural to urban areas across the country. Adapting new technologies is inevitable to meet the economical expectations and tight completion periods. The construction industry is adapting cutting-edge technologies by deploying state-of-the-art machineries, innovative construction techniques, end-to-end digital solutions etc – all of which ensure the highest safety and quality standards.
The Indian construction industry is evolving rapidly to reach the top technologies being followed globally. Top players in the industry are at par with their counterparts in developed countries. However, this adaption is yet to percolate down to the medium and small players.
What are the challenges in construction of deep foundations in India with respect to project type, size, and jobsite condition?
The main issue is inadequate investigations at the tendering stage. This poses a huge risk for execution agencies, resulting in cost and time overruns. Most of the times, on-the-spot patchy solutions are deployed to overcome the geotechnical uncertainties.
Availability of skilled manpower in the construction industry is becoming an issue. Deep foundation, being technology-oriented, requires a trained workforce – which is being addressed mainly by coordinating with OEMs for training personnel.
Introduction of latest technologies takes a bit of time to convince the clients in the absence of codes and precedence in India. Constant dissemination of information among the industry stakeholders, along with the educational institutions, is a must to get a quick buy in.
After the lull induced by Covid-19, the construction industry has opened up with a large number of projects, leading to a spike in the use of highly specialized equipment. This poses a huge challenge in resource levelling.
What is the impact of inadequate geotechnical investigations on the structures being built?
In most of the cases, the project development authorities are under time pressure to get the project moving to the execution phase. Also, they are inadequately advised to conduct a quick geotechnical investigation, where even the land acquisitions are not complete, hence, investigations are carried out in available areas and not at the required locations.
Inadequate investigation becomes a stumbling block for taking proper foundation solutions and it causes inordinate delays, cost overruns, and disputes. Proper investigation on award of job is the need of the hour to mitigate the risks. This requires a proper time allowance for this activity and it will also save project completion time.
How important is geotechnical investigation in selecting the appropriate piling and pile foundation methodologies for a project?
A well-planned geotechnical investigation campaign to suit structural and functional requirement by an experienced and qualified geotechnical engineer, is the best starting point in deciding the appropriate piling and pile foundation methodologies.
While devising an investigation program, more emphasis should be given on use of proper GTI equipment to reduce errors in collecting the field data. Presence of qualified geologist for supervising and logging field data is a must since the entire investigation pivots on in-situ information. Laboratory testing is a requirement to assess the physical properties, but caution and engineering judgement must prevail to avoid unnecessary testing of consolidation and triaxial tests, especially for pile foundation.
What are the challenges in design and construction of pile foundation in non-liquefiable and liquefiable soil?
Major challenge is a highly varying stratification even within a project site which requires a detailed investigation to arrive at optimum solutions in terms of zoning of treatment areas. Hence, collection of field data (SPT & ECPT) and proper soil classification at lab is vital. Also, after treatment, post-investigations are a must to ensure adequate safety against liquefaction.
What are the benefits of CFA (Continuous Flight Auger) Pile Technology?
CFA is an emerging solution for medium to short deep piles with smaller dia. It is comparatively a faster, cleaner and greener solution. The absence of Indian code for CFA is delaying its adoption.
What is your view of the skill development programs in India specific to geotechnical engineering and foundation/underground structure construction?
There are no organised skill development programmes specially for geotechnical engineering. Our needs are met by a specific in-house structured skill development program in consultation with specialized OEM manufacturers.
We are seeing a surge in infrastructure development, resulting in deployment of specialized foundation equipment. Consequently, the availability of trained manpower is a concern as everyone is competing for the limited resources. A certified skill development programme will address this issue and pave the way for enhancing the quality of work being done.
What are the various codes, standards, and guidelines in India for design, installation, construction, and testing of pile foundation and excavations?
Pile Foundation
- Design: lack of guidelines for selection of shear strength parameters
- Bidirectional load test: interpretation of test is speculative in the absence of IS code
- Cross Hole Sonic Logging Test: introduction of CHSL to assess quality of piles without interpretation guidelines/IS code is leading to speculative repair methodologies
- Standardisation of codal requirements (IS, IRC, RDSO)
Excavation
- Since no standard guidelines in India, international guidelines are being followed. Guidelines for Indian geological conditions to be framed.
What, according to you, are the right practices for Quality Control/Quality Assurance of deep foundation testing?
Initial load testing of piles is the right practice for assuring QAQC and overall performance of A deep foundation. However, insistence on doing the tests at cut-off level must be reviewed and an alternative methodology to conduct the load test at ground level will help in reducing the project cycle.
Routine load tests are also a good way of ensuring the QAQC of the overall product. Dynamic testing is gaining acceptance as it reveals overall health and capacity of piles. In critical areas, 100% PIT ensures QAQC.
CHSL is increasingly becoming a method to ensure QAQC of piles, in spite of DFIs guidelines indicating this is not a conclusive evidence. This must be deliberated by the fraternity and detailed guidelines for interpretation of CHSL results and repair mechanism should be suggested. For diaphragm walls, KODEN with Low Strain Integrity testing ensures QAQC.
What geotechnical solutions are being offered by L&T, especially in areas prone to earthquakes and landslides?
We offer an entire range of geotechnical solutions including Dams, Barrages & Weirs, In-Stream Storage Structures, Deep Foundation Supported Bridges, Berths & Jetties, Dry Docks, Slipways & Wet Basins, Inland Waterway Terminals & Navigational Locks, Fisheries Harbour, Breakwaters, Drilling & Grouting, Cut-off Wall, River Development & Shore Protection, Deep Shafts Deep Basements, Intake Structures with Approach Bridges, Ground Improvement Works, Large Diameter Piling, Diaphragm Wall, Secant Pile Wall, Sheet Pile Wall, Contiguous Pile Wall, Barrette Piles, and Soldier Piles.
Trench cutter in operation. Cage fabrication yard in foreground.
Please share one challenging project of geotechnical engineering and deep foundation which not only saved time and cost but also ensured safety of the engineers.
There are many innovative solutions provided by L&T, we are presenting a case study which was a game changer for creating intake structures. L&T had provided innovative solution using diaphragm wall techniques to create multi-cellular intake structures as against a traditional approach of time-consuming construction of intake wells, which resulted in significant reduction in project time and cost.
Given below is a report on the Lift irrigation Project at Pattisam, Rajahmundry, in AP.
This fast-track lift irrigation project comprised of construction of intake structure on Godavari riverbank, twenty four pumps of capacity 12 cumecs, twelve numbers of 2m diameter pipeline of length approx. 4km, construction of switchyard, sub-station etc. The approx. value of the total project package was about `1500 cr. The construction duration for the entire project was about 12 months starting March 2015.
L&T GeoStructure scope: Out of the major portion of the construction, L&T Geo’s scope was limited to:
- Construction of intake chambers using diaphragm wall technology
- Excavation inside the chamber
- Piling of 100 nos. to support pipeline
The contract value allotted to L&T Geo was 97 cr.
The intake structure consisted of twenty-four chambers to accommodate motors and pumps, and end chambers for maintenance purpose. Our scope was to construct only diaphragm wall upto ground level (+22.50m). The structure above ground level was part of the main contractor MEIL scope. Concrete, rebar, couplers and embedded parts were free supply.
Total number of panels : 189 (936 linear metre)
Panels completed as on 5 July 2015 : 35 nos (221 linear metre)
Size of chamber : 220m L x 20m W x 27m D
Land available for operations : 250m L x 50m W
Thickness of diaphragm wall : 1200mm
Total concrete quantity : 35000 cu.m. (7200 cu.m. completed as on date)
The contract LOI was received by L&T Geo on 4 March 2015, and contract duration was 180 days from receipt of mobilization advance, which was received on 20 April 2015. Later, there was a quantity variation of +35% and the project duration was extended till 31st March 2016
Equipment mobilized:
- One number trench cutter
- Three numbers high-end hydraulic grabs
- Seven numbers of cranes ranging from 50 -180T capacity
- All other accessories like welding / cutting machines, generators, pumps, desanders, bentonite system are mobilized and established
In the month of June 2015, work had stopped temporarily due to river water flooding upto ground level. This forced us to move the equipment to safer higher elevation. Work was later started in full swing on 24 June 2015.
We had analysed and deployed required resources to carry out the work. It is clear from the site pictures, that there was no further space for deploying additional equipment at this juncture. This was conveyed to the authorities.
Our site was operating 24x7 under the leadership of Mr. Sanjeevi Perumal, who had worked with Bauer Malaysia for more than two decades, prior to joining L&T Geo. Similarly, the site personnel were with special experience to carry out diaphragm wall work and everyone was motivated and geared up to achieve the target by March 2016.
This project had a very strong political influence and involvement and hence, we were pressurized to reduce the duration drastically to showcase the same from their end. Careful resource planning, mobilization of manpower and expertise let us to complete the project on time as we completed the project by March 2016 and got the appreciation from the customer.
How do programs like the DFII increase awareness of the importance of geotechnical and foundation investigations?
We welcome and actively participate in the programmes organised in the industry. Knowledge dissemination is a must to bridge the gap amongst educational and research institutions, the engineering fraternity, and technology developers. DFII needs to position itself with institutions and governing agencies in bridging and bringing new technologies and standardisations.
