Technology
Ground improvement designs
Published
4 years agoon
By
admin
Santanu Saha, Haldia, W.B. and Dr. Sudhendu Saha, W.B. highlight the need of a good design of ground improvement with stone columns with a major focus on ground improvement using stone columns and band drains for foundation of large diameter storage tanks.
IMPROVEMENT of strength and compressibility characteristics of soft or weak subsoil, by use of various forms of vertical drains with preloading and/or by installation of stone columns as load bearing elements have been identified as an effective means of ground improvement technique. The field application of technology has developed faster than the design methodology, as the composite behaviour of stone columns and the surrounding soil present a complexity of behaviour, both in terms of load sharing capacities and settlements. The vertical drains including geosynthetic band drains, when associated with pre-loading improves the shear strength and reduces the compressibility of clayey soils by achieving accelerated consolidation under imposed loads. The basic principle involved is that of three dimensional consolidation involving a combination of vertical and radial drainage. The most significant work in this field came from Barron (1948) who incorporated the effects of radial drainage. Later, Hansbo (1979) gave solutions considering effects of smear and well resistance. A method for calculating the degree of consolidation under combined effects of vertical and radial drainage was also presented by Carillo (1942). This paper presents the salient features of the design method adopted for ground improvement for foundations of large crude oil storage tanks. The existing subsoil deposits, the scheme of innovative optimal ground improvement technique executed, and tank performances during hydro testing have been presented.
Subsoil conditions
The subsoil at the site (Haldia), as revealed in soil investigation, comprised compressible clayey soil strata. The upper soil strata of soft silty clay with decayed vegetation extended up to average depth of about 9 m from existing ground level in low- lying area, which was proposed to be developed by about 1.5 m to achieve the finished ground level. The soil strata below 9 m were about 6 m thick non plastic gray clayey silt and fine sands, underlain by about 11 m thick soft silty clay with decayed vegetation. The soil strata below up to about 26 m were stiff to hard silty clay and dense silty sands. The undrained cohesion of subsoils varied from 25 to 45 kN/m2, and coeff. of volume compressibility varied from 2.3 x 10-4 to 3.9 x 10 -4 sq.mIkN corresponding to pressure range of 50 to 100 kN/sq.m. The N-value varied from 2 to 5.
The coefficient of consolidation for pressure range 50 to 100 kN/sq.m varied from 6.70 XlO -4 em- /sec to 11.2 X 10 -4 em / sec.
Design approach
The load bearing capacity of the virgin ground under proposed uniform circular loading below large tank foundations were estimated to be about 80 kN/sq.m, which was far less than the required design bearing capacity of 160 kN/sq.m under proposed construction of large crude oil steel floating roof storage tanks of capacity 60,000 kL, 79 m in diameter and 13.5 m high with total empty weight of 1375 tonne. A number of ground improvement techniques including piles were available which could be used for design of foundations for large oil storage tanks. However, for selection of an appropriate design for techno-commercial assessment in respect of each alternative turn out to be in favour of ground improvement using stone columns, since:
- The length of stone columns would significantly be shorter than piles as it is not necessary to extend the stone columns to a hard stratum ( Bhandari 1998 ).
- Stone columns can withstand large drag forces without getting their load transfer characteristics hampered unlike piles (Madhav 1994).
The beneficial effects of installation of stone columns in weak or difficult subsoil deposits is manifested in the form of increased load carrying capacity and significant reduction in settlements. In similar situations, in recent past, stone columns have been successfully used (Bhandari 1983, Hughes & Withers 1974) for improvement of ground, particularly for storage tank foundations.
Alternatively, vertical drains like sandwicks, band drains, etc, associated with pre-loading, could also be used. Such vertical drains themselves do not share any part of superimposed loads, except providing only drainage paths for accelerating consolidation of the ground under pre-loading. The preloading technique, although quite effective, have major limitation of long time duration together with high cost of pre-load materials, and the environmental hazards associated in its use and disposal, particularly in a running industrial plant areas. For the proposed construction of floating roof crude oil storage tanks of 79 m diameter and 13.5 m high, the total expected average settlement of the virgin ground at centre, at R/2 and at periphery of tanks were approximately estimated to be 950 mm, 900 mm and 465 mm respectively. Such long-term large settlements are not acceptable for the satisfactory performance of storage tanks. As such, the ground improvement scheme had to be so designed to reduce the possibility of excessive settlements and at the same time such reduced consolidation settlements to occur prior to installation of the tanks to operation.
Ground improvement technique
It was observed that subsoils upto average depth of about 9 m was highly compressive with very low bearing capacity. For improvement of load-bearing capacity of the ground, installation of stone columns was considered to be appropriate. Since the load-bearing capacity of stone columns and the treated ground do not depend on the length of stone columns beyond critical length, which is about five or six times the diameter of stone columns, and as the upper compressible strata extended only about 9 m below existing ground level, underlain by fine silty sand layer, the length of stone columns which was considered adequate is only 8 m. The lower soil strata extending up to about 26 m below ground level was also highly compressible, underlain by stiff to hard silty clay and dense sands. As such, treatment of the ground upto at least 26 m was considered essential. This could be achieved only by installation of vertical drains like very cost effective geosynthetic band drains up to depth of 26 m.
The unique combination of stone columns and geosynthetic band drains for improving the ground for foundations of large storage tanks was adopted for the first time in reducing the depth of stone columns. The deep installation of band drains helped in reducing the time of consolidation process of soil under surcharge loads during construction and also during hydro testing of tanks.
Load-bearing capacity of treated ground
After installation of stone columns, and geosynthetic band drains, sand pad foundations were constructed. The steel storage tanks are generally constructed in place over the sand pads.
The hydrotesting of tanks are taken up subsequently. In the present case, about 25 per cent of the design load was actually applied during construction of sand pads and steel tanks. As a result, during this period, the treated ground got partially consolidated under construction activities. Due to rest time after ground treatment, the consolidated undrained cohesion of soil would reasonably be increased to at least 45 kN / sq m. With this value of cohesion, the safe lead bearing capacity of stone columns was estimated as (Saba 1992) P.lFS= Psafe = Ap[(Yz +q,)K+qs (1+2K)/3+ 4C]Net>
where,
Y = submerged unit weight of soil,
z = depth of bulge = 2d
d = finished diameter of stone columns
qs = surcharge on surrounding soil
K = Earth pressure coefficient
A = cross sectional area of stone column ES. = facor of safety
p Net> = tan? (45 + 4>/2)
4> = angle of internal friction of compacted stones
The safe bearing capacity of treated composite ground may be estimated as
Q _, = [(A – A ) q + Psaf ] / A
S
A = Influence area of each stone column = 0.868 S2
S = spacing of stone columns in triangular grid
Peripheral concentration of stone columns was provided to prevent any possibility of lateral movement of subsoil and to provide extra stability to edges of sand pad foundations.
Settlement analysis
A typical estimate of total probable consolidation settlement of virgin soil strata, under tank loadings were calculated using the average thickness of different strata , and the average values of coefficients of volume compressibility. The long-term consolidation settlement is normally calculated as follows:
S = A. L H. mv . ilp
where,
A. = factor depends on pore pressure parameter
H = thickness of respective soil strata,
m, = coefficient of volume compressibility of respective soil strata
ilp = increase in effective pressure at mid-depth of respective soil strata.
The total probable consolidation settlement of the ground treated with partially penetrating stone columns up to 8 m below existing ground level, and band drains upto 26 m below GL in the tank pad areas was estimated as S, = &+ilH .where, & = probable settlement of stratum reinforced with stone columns
Settlement criteria
Large steel storage tanks are fairly flexible structures and transmit the weight of the liquid content to the foundation as uniformly distributed load. The bottom plates can easily withstand considerable differential settlement. But the vertical shell because of thinness may be distorted by differential settlement along the periphery, and this may lead to ovality of floating roof tanks. To avoid tension in the bottom plate, the safe permissible change of slope between edge and centre of tank is about 2.23 per cent (Penman 1977). The initial slope of top of sand pad was provided accordingly. To minimise the possibility of shell distortion, the shells are constructed on annular bottom plates which in turn founded on crushed stone ring beam.
In view of above considerations and past experiences, the following settlement criteria were recommended for the 79 m diameter 13.5 m high floating roof storage tanks:
-
The average total settlement at periphery during and at end of hydro test shall be limited to 400 mm.
-
The differential settlement along tank periphery measured at cleats on shell shall not exceed 1 in 300.
-
The maximum differential settlement between diametrically opposite points on the tank periphery shall not exceed 150 mm .The hydrotestings of tanks had already been completed successfully satisfying the above design criteria to demonstrate that the present innovative design concept is very much cost effective and based on sound theory and practice. Since about 25 per cent of load was applied during construction period causing about 25 per cent of expected settlement to occur before actual hydrotesting was taken up. As such the total average settlement that was recorded at tank periphery at the end of hydrotest was only about 200 mm.
Conclusions
Design of ground improvement with stone columns has not been standardised yet. Many authors have attempted various semi-emperical methods of design using stone columns. A few theoretical approaches have also been attempted by the researchers, idealising the soil-stone column system.
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Economy & Market
RAHSTA Roundtable Sets Agenda for Smarter, Safer Highways
Published
1 week agoon
March 16, 2026By
admin
Roundtable discussions focus on innovation for safer highways.
Held on 12 March 2026 at Courtyard by Marriott, Mumbai, alongside the Infrastructure Today Airport Conclave, the RAHSTA Roundtable brought together stakeholders from across the highways and infrastructure ecosystem to shape the agenda for the 16th RAHSTA 2026, scheduled for 8–9 July 2026 at the Jio Convention Centre, Mumbai. The session focused on key industry themes including road construction, technology, safety and long-term sustainability.
Opening the discussion, Pratap Padode, Founder, FIRST Construction Council, said the roundtable marked the beginning of a broader consultative process leading up to the July event. The aim, he noted, is to bring together industry stakeholders to refine the agenda for discussions on the future of roads, bridges, tunnels and allied infrastructure.
Padode noted that while central road project awards have slowed in recent years, states are increasingly driving the next phase of infrastructure growth. Maharashtra, with its long-term road development plans and agencies such as MSRDC and MSIDC, is expected to play a significant role in this expansion.
RAHSTA Expo 2026 as a specialised platform dedicated to road infrastructure, covering highways, tunnels, bridges and flyovers along with construction technologies, safety systems and maintenance solutions. He also highlighted the growing importance of rural connectivity and said the organisers are engaging with government bodies to highlight rural road development initiatives.
Tanveer Padode, CIO, ASAPP Info Group, presented insights from IMPACCT, the group’s infrastructure intelligence platform. He pointed to a strong project pipeline despite slower highway awards earlier in the year, noting that states such as Maharashtra, Odisha and Arunachal Pradesh are emerging as key drivers of new projects. The data also revealed that only a small group of contractors participates in large-value infrastructure bids.
Lt Gen Rajeev Chaudhary, former Director General, Border Roads Organisation and Chairman of the RAHSTA Expo Committee, emphasised the need for stronger collaboration across the ecosystem, including policymakers, contractors, technology providers and financiers. He also called for addressing systemic issues within the sector and encouraged greater participation of women in infrastructure leadership.
The discussion also explored the evolving economics of road development. Phani Prasad Mandalaparthy, Associate Director, CRISIL Intelligence, noted that the slowdown in project awards reflects a shift towards higher-value logistics corridors rather than simple road widening projects. However, private participation through BOT and TOT models remains limited.
From the contractors’ perspective, Sudhir Hoshing, Whole-Time Director, Ceigall, said companies are becoming more selective in bidding, favouring projects with clearer payment mechanisms and efficient processes. While NHAI continues to offer greater operational clarity, states such as Uttar Pradesh and Bihar were cited as relatively supportive environments for project execution.
Durability and sustainability also emerged as key themes. Himanshu Agarwal, COO – Road & Infrastructure, Zydex Group India, highlighted the need to prioritise lifecycle performance and resilient pavements, while participants discussed the potential of alternative materials such as plastic waste, steel slag and industrial by-products in road construction.
Dr LR Manjunatha, Vice President, JSW Cement, emphasised that India has abundant fly ash, slag and other industrial materials that can improve durability and sustainability if integrated into specifications and policy frameworks.
Technology and equipment challenges were also discussed. Dr Lakshmana Rao Mantri, Dy General Manager, Afcons Infrastructure, highlighted the shortage of tunnel boring machines (TBMs), which is delaying several underground infrastructure projects. Participants agreed that developing domestic TBM manufacturing capabilities will be critical for future infrastructure expansion.
The future of concrete pavements was another area of discussion. Dr V Ramachandra, President, Indian Concrete Institute, stressed that the debate should focus on lifecycle performance rather than material choice alone, noting that evolving design standards are improving the feasibility of concrete roads.
Prof Dharamveer Singh of IIT Bombay added that while India has made significant progress in infrastructure development, stronger capacity building and better execution practices are essential to ensure consistent road quality.
The discussion also touched upon technology adoption in the sector. Rushabh Mamania, Partner & CBO, Roadvision, highlighted the growing role of AI in road infrastructure, noting that AI-driven monitoring systems are already being deployed across large stretches of national highways.
Overall, the roundtable underscored that the future of highway infrastructure will depend not only on the pace of construction but also on durability, safety, technology integration and sustainable materials. The discussions offered valuable insights that will help shape the agenda for RAHSTA 2026 and guide future collaboration within the industry.
Economy & Market
CTS Roundtable Charts Tech-Led Roadmap for Construction
Published
1 week agoon
March 16, 2026By
admin
CTS Roundtable Maps Technology Roadmap for Construction
Ahead of the Construction Technology Show (Con Tech Show) 2026, industry leaders, technology innovators and academia came together in Mumbai to deliberate on how digitalisation, automation and industrialised construction can reshape the sector. The discussion made one thing clear: construction can no longer afford to treat technology as optional.
Held on 12 March 2026 at Courtyard by Marriott, Mumbai, alongside the Infrastructure Today Airport Conclave, the CTS Roundtable served as a precursor to the Construction Technology Show 2026, scheduled for 19–20 August 2026 at NESCO, Mumbai.
A platform to move from discussion to deployment
Opening the session, Pratap Padode, Founder and Editor-in-Chief, ASAPP Info Global Group, said construction technology has long remained close to his heart, especially given the sector’s traditionally slow pace of technology adoption. He noted that over the years, the Construction Technology Summit had steadily built interest, and the next step was now to expand it into a larger, more meaningful platform that could bring together technology providers, users, startups and innovators under one roof.
Padode said the vision for CTS is not limited to software alone. The platform aims to embrace all forms of technology that can improve construction efficiency, quality and execution—from digital tools and project management systems to lean construction, off-site fabrication and startup-led innovation. He also highlighted plans to deepen startup participation and create space for young companies to showcase emerging construction solutions.
Industry at a turning point
Moderating the roundtable, Naushad Panjwani, Chairman, Mandarus Partners, set the context by pointing out that the global construction industry, despite being a multi-trillion-dollar sector, continues to lag in productivity. He noted that while manufacturing has consistently improved efficiency, construction has remained slow to modernise.
Referring to both global and Indian trends, Panjwani underlined that the industry is now at a decisive moment. India, he said, is entering a major build cycle, and delivering the next phase of infrastructure and real estate growth through traditional methods alone is no longer viable. The goal of the roundtable, therefore, was not to debate technology in isolation, but to identify the most critical conversations that would bridge the gap between innovation and implementation.
His central message was clear: CTS 2026 must be shaped around themes that make CEOs, CIOs and CTOs feel they cannot afford to miss the event.
From BIM to AI, data to governance
A major theme that emerged through the discussion was the need for better data, better visibility and better decision-making. Dr Venkata Santosh Kumar of IIT Bombay echoed this, saying that the underlying data infrastructure itself needs attention. Construction projects, particularly remote ones, often face issues around connectivity, data collection and data use. Without this foundation, more advanced technologies cannot deliver their full value.
Chandra Vasireddy, CEO & Co-founder, Inncircles, expanded the discussion to governance, arguing that technology must help connect the many moving parts of a construction business. For him, the real value of digital transformation lies in creating better governance, clearer visibility and stronger business outcomes.
Tejas Vara of Inncircles stressed the importance of timely site data for leadership teams, especially in large and remote projects where decisions on materials, machinery and manpower often get delayed because information does not reach headquarters in time.
The role of AI also featured prominently. Rushabh Mamania, Partner and CBO, Roadvision said that while AI and machine learning are now common terms, vision intelligence and language intelligence have still not deeply penetrated the construction sector. He emphasised that startups in India are building relevant AI-led solutions and are already attracting international interest, showing that innovation need not be imported—it can be built locally and scaled globally.
Industrialised construction gains ground
The roundtable also placed strong emphasis on industrialised construction methods. Kalyan Vaidyanathan, CTO – Construction & R&D, Tvasta, called for greater focus on off-site fabrication and the broader industrialisation of construction. Bhargav Jog, General Manager, Dextra, highlighted precast technology and alternative sustainable materials as areas with immediate relevance.
Several participants agreed that modular, precast and pre-engineered approaches are no longer niche ideas. They are increasingly becoming practical responses to the sector’s challenges around labour shortage, timelines, quality control and predictability.
Anup Mathew, Sr VP & Business Head, Godrej, argued that the industry needs a fully integrated approach—from design and procurement to execution and asset management. Unless these are connected, technology adoption will remain fragmented and sub-optimal. He pointed to pre-engineered and modular systems as examples of how industrial thinking can compress timelines, improve quality and reduce dependence on difficult on-site conditions.
Adoption remains the biggest hurdle
While there was broad agreement on the promise of technology, the discussion repeatedly returned to one fundamental challenge: adoption.
Abhishek Kumar, COO, LivSYT, observed that the market is crowded with solutions, but many buyers still struggle to evaluate which technology suits which use case. According to him, the industry needs clearer frameworks to help users select, compare and adopt solutions, rather than expecting a single platform to solve every problem.
Dr Tenepalli JaiSai, Associate Professor, School of Construction(SoC), NICMAR University, noted that isolated technologies will not solve the productivity problem by themselves. What is required is an integrated Construction 4.0 approach, where digital, physical and cyber-physical systems work together rather than in silos.
That concern around silos was reinforced by Subodh Dixit, former Director, Shapoorji Pallonji, who said the issue is not just that technologies are disconnected, but that stakeholders are as well. Clients, consultants, contractors and partners often operate with different priorities. Unless these silos are broken, technology will struggle to percolate across the full project value chain.
Harleen Oberoi, Project Management, Tata Realty shared a practical perspective from the client side, saying that successful BIM implementation requires investment across the ecosystem, not just within one organisation. Trade partners, vendors and other stakeholders must also be trained and aligned if the technology is to deliver its intended results.
Beyond buzzwords
A notable takeaway from the session was that the industry is moving past the phase of treating technology as a buzzword. Participants repeatedly stressed that the real question is not whether technology should be used, but where it creates measurable value and how that value can be scaled.
The conversation also expanded beyond mainstream themes to include repairs and rehabilitation, construction and demolition waste, sustainability, circular economy, green sourcing, carbon measurement, design interoperability, generative design, robotics, and the role of horticulture and greener built environments.
Setting the agenda for CTS 2026
By the close of the session, the roundtable had surfaced a strong set of themes for the upcoming show: BIM and digital twins, AI and data platforms, industrialised construction, startup innovation, governance-led technology adoption, robotics, sustainable materials, and integrated project delivery.
More importantly, the session established CTS 2026 as more than an exhibition. It is shaping up to be a serious industry platform where users, technology providers, researchers and policymakers can collectively define the future of construction.
As Padode noted in his closing remarks, the conversation will continue through further consultations and possibly webinars in the run-up to the show. If the roundtable is any indication, CTS 2026 will aim not merely to showcase technology, but to push the industry towards meaningful adoption at scale.
Ponnusamy Sampathkumar, Consultant – Process Optimisation and Training, discusses the role of skilled operators as the decisive link between advanced additives, digital control and world-class mill performance.
The industry always tries to reduce the number of operators in the Centre Control Room. (CCR) Though the concept was succeeded to certain extent, still we need a skilled person in the CCR.
In an era where artificial intelligence (AI) grinding aids, performance enhancers, and digital optimisation tools are becoming increasingly sophisticated, it’s tempting to believe that chemistry alone can solve the challenges of mill efficiency. Yet plants that consistently outperform their peers share one common trait: highly skilled operators who understand the mill as a living system, not just a machine.
Additives can improve flowability, reduce agglomeration, and enhance separator efficiency, but they cannot replace the nuanced judgement that comes from experience. Grinding is a dynamic process influenced by raw material variability, moisture, liner wear, ball charge distribution, ventilation, and separator loading. No additive can fully compensate for poor control of these fundamentals.
Operators see what additives cannot
When I joined the cement industry in 1981, not much modernisation was available then. Mostly the equipment was run from the local panel. Once I was visiting the cement mills section. The cement mills were water sprayed over the shell to reduce the temperature to avoid the gypsum disintegration.
The operator stopped the feeding for one of the mills. When I asked the reason, he replied that mill was getting jammed, and he added that he could understand the mill condition by its sound. I also learned that and it was useful throughout my career. In another plant I saw the ‘Electronic Ear,’ which checked the sound of the mill and the signal was looped with feed control!
Whatever modernisation we achieve, it is from the human factor that the development starts.
Additives respond to conditions; operators interpret them.
A skilled operator can detect subtle shifts, like a change in mill sound, a slight variation in circulating load, or a drift in separator cut point. It’s long before instrumentation flags a problem. These micro-observations often prevent major efficiency losses.
Additives work best when the process is stable
I would like to share one real time incident. The mill was running on auto mode looped with the mill outlet bucket elevator kilowatt. (KW)There was a decrease in the KW, and the mill feed was increased by the auto control (PID). After a while, the operator stopped both the feed and the mill. He asked the local operator to check the airslide between mill outlet and the elevator. They found the airslide was jammed and no material flow to the elevator!
The operator deduced the abnormality by his experience by seeing the conditions and the rate of increase of the feed by the auto control.
It’s always the human factor that adds value to the optimisation.
Grinding aids are multipliers,
not magicians.
They deliver maximum benefit only when:
• Mill ventilation is correct
• Ball charge is balanced
• Feed moisture is controlled
• Separator speed and loading are improved
• Blaine targets are realistic
Without these fundamentals, even advanced additives may become costly investments. The operator is responsible for ensuring process stability, whether using a ball mill or a vertical mill. After ensuring the system is stable, the operator observes it briefly before transitioning to automatic control. If there is any anomaly in the system the operator at once takes control of the system, stabilises and bring back to auto control.
Skilled operators adapt in real time
It will be interesting to note that the operators who operate from local panel start to operate from DCS also. They have the experience and the ability to adapt the changes. Operator checks each parameter deeply. Any meagre change in the parameters is also visible to him.
Raw materials change. Weather changes. Wear patterns change.
A skilled operator adjusts:
• Feed rate
• Water injection
• Separator speed
• Grinding pressure (in VRMs)
• Mill load distribution.
These adjustments require intuition built from years of experience, something no additive can replicate.
Human insight prevents over reliance on additives
Plants sometimes increase additive dosage to mask deeper issues like:
• Poor clinker quality
• Inadequate drying capacity
• Incorrect ball gradation
• High residue due to worn separator internals.
A knowledgeable operator finds root causes instead of chasing temporary chemical fixes.
The real optimisation sweet spot is reached when:
• Operators understand how additives interact with their specific mill.
• Additive suppliers collaborate with plant teams.
• Process data is interpreted by humans who know the mill’s behaviour.
This constructive collaboration consistently delivers:
• Lower kWh/t
• Higher throughput
• Better product consistency
• Optimum standard deviation.
Advanced additives are powerful tools, but they are not substitutes for human ability. Grinding optimisation is ultimately a human driven discipline, where skilled operators make the difference between average performance and world class efficiency. Additives enhance the process but operators
control it.
About the author:
Ponnusamy Sampathkumar, Consultant – Process Optimisation and Training, is a seasoned cement process consultant with 43+ years of global experience in plant operations, process optimisation, refractory management, safety systems and training multicultural teams across international cement plants.


