Deep Foundations for Infrastructure Development in India

This paper highlights salient features of an excavation 38 m (Length) by 10 m (Width) by 24 m (Depth) carried out in Central Kolkata. Secant pile wall (SPW) formed using a combination of alternating 1200 mm and 800 mm diameter piles was used. Six layers of struts and waler beams including bottom slab were utilized as lateral restraints to piles. The geotechnical profile for excavation zone was predominantly silty sand to sandy silt. The profile is characteristic of river channel deposit usually encountered in Kolkata. Temporary stage analysis (including seepage analysis) and design were carried out in FEM software. Design checks for clay bursting, piping, bottom heave, etc. were also carried out. Extensive instrumentation and monitoring were carried out during the excavation period to check parameters such as ground movement, pile movement, piezometric heads, etc. as per review levels. During excavation, ground improvement using Tube-a-manchette grouting technique was also required to be carried out as per field observations. The paper discusses some of the major challenges faced as well as measures taken to counter them, during deep excavation carried out in silty soils in a very congested urban setting in the heart of a Megacity.

Down-The-Hole (DTH) drilling usually uses compressed air to power the hammer. However, there are now DTH hammers on the market which instead of compressed air use high pressure water to power the hammer. There are several benefits with using water DTH compared to air DTH, which are discussed in more detail in this paper. From a physics point of view, many of the benefits arise from the fact that water is an incompressible media and air is not. Energy consumption is roughly a quarter compared to air, resulting in lower carbon emission and a lower energy bill. In the case of water DTH, the water leaving the drill bit in the hole is at a low velocity and ambient pressure. However, with air DTH, the air leaving the drill bit in the hole is at a high velocity and high pressure. This means that the risk of damaging surrounding structures in sensitive areas such as urban environments and dams is greatly reduced with water DTH. In this paper, two cases where water DTH is used in jet-grouting applications are discussed in detail. As these cases show there is a clear improvement in productivity when using water DTH hammers.

As a part of Mumbai City Mega Drinking Water Project at Amar Mahal Tunnel-1 Ghatkopar East Mumbai, drinking water tunnels were proposed by MCGM from Amar Mahal to Trombay reservoirs, Amar Mahal to Wadala and further up to Parel. The pipeline has to be underground and laid at a depth of 5.5 m. The initial proposal was to provide sheet piling to enable the safe excavation and installation of underground pipeline. However, installation of sheetpiles was practically not feasible due to the existing soil strata for driving the sheet piles. Hence, it was proposed to install micropiles instead of sheet piles. In this paper, we discuss about the purpose, basic design, detailed design approaches and actual work implementation of micropile with temporary struts for shoring protection works in this project.

Bauer Egypt was commissioned with the specialist geotechnical engineering works for 18 out of the total of 22 underground stations on Metro Line 3. Cumulated amounts of approximately 600,000 m² of diaphragm wall (D-wall) and 58,000 m² of silicate gel grout plugs were executed for open excavation pits. In addition to the daily challenges, particular efforts are worth highlighting: for recovering a tunnel boring machine (TBM) of the client, a diaphragm wall shaft 100 m deep using a natural clay layer acting as a bottom plug was constructed, to allow for horizontal drilling and subsequent soil freezing measures out of the shaft; also the deployment of low-headroom units to continue the D-wall works near and under existing bridges; and finally, special jet grouting works were executed at an intersection between an existing sewer and the TBM route.

Bangalore Metro Rail Project Phase II is one of the technologically challenging projects, specially construction of underground metro rail system. The Bengaluru city is very congested and connection of metro rail system with existing transportation networks is equally challenging. In this Phase II of construction, the underground metro is being constructed by blasting hard rock formation and supporting the shear zone. Most of the subsurface rock formations comprises of Granitic Gneiss formations are of Precambrian age and shear zones that includes friable a thin weathered rock formation. With such subsurface geological conditions, the anticipated construction challenges include: (A) deep excavation of hard rock mass under old and sensitive structures and buildings, by controlled blasting; (B) variation in the rock grade from grade I to grade V; (C) weak rock mass at shear zone resulted in planar failure beneath the retaining wall; (D) water seepage along shear planes; (E) selection of a suitable method to conduct blasting near high-voltage electrical machinery or power cables. This paper describes the methods adopted to mitigate these technological challenges and to meet stringent environmental compliances. These include study and application of various geological, geotechnical parameters to develop a proper line drilling and controlled blasting techniques to minimize the ground vibrations and controlling the rock fragmentation and to optimize the equipment performance in terms of productivity and time schedules. The “Phase 2” software of “Rocscience” has been used and regression analysis was carried out by using MCD (Maximum Charge per Delay) and PPV (Peak Particle Velocity) to estimate with FOS (Factor of safety) for sensitive places such as nearby high-rise buildings and electrical transformers.

Construction in congested urban areas has necessitated tall and massive structures. In urban areas, it is common to construct underground structure nearby existing buildings. Selection of an appropriate support structure system to be implemented in the excavation in an urban area is heavily dependent upon the geotechnical conditions and safety of the surroundings and neighbouring structures. Urban Rail, popularly referred to as Metro Rail, has seen substantial growth in India in the recent years. More cities are experiencing the need for metro rail to meet their day-to-day mobility requirements. The metro structures involved deep excavation for foundations, which induces the stresses and thereby alters the existing equilibrium and thus may affect the stability of neighbouring structures considering safety point of view. Hence, design and execution of deep excavations become one of the important challenging tasks of any geotechnical engineer in the modern era. Further, it is important to control the ground movement in order to prevent the failure of excavations. This involves specialized foundation technologies, usage of sophisticated equipment and new methods in underground construction, safety and monitoring systems. In this paper, the methodology used for protecting adjoining structures due to deep excavation for Nagpur Metro station is studied.

A geotechnical forensic evaluation of piles for an industrial facility in Haryana was performed to assess the quality of the piles and to evaluate piles installed using two different types of rigs. Low-strain pile integrity tests were performed on all piles to assess the pile length and possible presence of structural defects. Coring was done through questionable piles for the clinching evidence of concrete quality and pile length. Probe holes adjoining piles helped confirm the bulging of piles at shallow depth. The paper highlights the importance of implementing a well-planned quality assurance program to confirm that all piles installed are of the desired quality.

This paper explains how BAUER Spezialtiefbau GmbH uses digital methods on projects—starting from work preparation to completion of works. More precisely, the advantages of BIM-based planning during work preparation and the automated and structured data management—both machine production data and the manually recorded quality-relevant reports—during execution phase are displayed. In this context, the benefit of the digital twin to optimize processes, to reduce defect costs, for a more effective reporting system, and the further usage of as-built information in the BIM or GIS process are described.

Excavation and shoring adjacent to the above-grade Gilmore train station and elevated guideway was undertaken in 2019. A perimeter secant pile cut-off wall was constructed to a depth 37 m (121 ft) below ground surface consisting of 1.0 m (3.3 ft) diameter drilled piles spaced 750 mm (2.5 ft) on-center, tied back with soil anchors, and reinforced with W610 steel sections every fourth pile. A bracing/jacking system was also constructed to support three free-standing guideway caissons within the excavation. An automated instrumentation program was installed to monitor movements of shoring walls and train infrastructure in real time and consisted of a robotic total station, inclinometers, tiltmeters, strain gauges, extensometers, and anchor load cells. Baseline monitoring was able to establish diurnal and seasonal movements within the structure, strongly correlated with temperature. The system actively monitored various shoring elements and train infrastructure in real time and alerted the project team when values exceeded predetermined threshold values. Remote reconfiguration of the automated system allowed for more frequent monitoring during jacking of Pier 29 in March 2022. Monitoring data were in agreeance with on-site manual surveying results and jacking dial gauges and proved to be a reliable monitoring system for construction applications.

Low Strain Pile Integrity Testing has been used in India since 1990s and several have tried to demonstrate the utility and benefits of this method. However, the use of this technology was limited till 1998 as not enough data maybe were not available to justify its use and application on major infrastructure and real estate projects. The first author has done significant work in this method resulting in its use in practically all sectors of the industry that use concrete bored pile foundations as a supporting element. The paper explains various signal enhancers or modifiers involved in processing of low strain test data and its implication on the final output. It also describes how the method can lead to abuse or can provide poor interpretation if incorrectly used. The current effort is to demonstrate that data collection and evaluation become complex with changes in soil stratum and pile profile. The paper highlights the present testing practices and provides a guideline for the classification of pile integrity into few simple categories in Indian context rather than writing complex interpretations.

Being a rapidly developing country, India is undergoing a massive infrastructure phase change remarkably. The construction industry is already set to boom, but the time and space constraints necessitate the employment of heavy plants and machinery to take the foundations deeper than ever. Operating such machinery on soft or poor ground conditions without a good working platform leads to uncertainties with massive loss of men and machinery. Plenty of such cases can be observed on construction sites across the globe. Unfortunately, forming a temporary working platform is given least to no importance in the construction industry, particularly ground engineering. This glitch can only be addressed through standard guidelines or codal recommendations on designing and implementing temporary working platforms issued by regulatory bodies. The present paper highlights the importance of providing the working platform, existing design method for working platforms such as TWf 2019:02 of Temporary Works forum, Building Research Establishment BR470 and a brief discussion on the design and construction of the geosynthetic reinforced working platform with a case study is also included. A pitch has been made on the importance of Indian codes/guidelines for the design and construction of temporary working platforms. These guidelines will ensure the safety of the men and heavy machinery and, in addition, increase the productivity of foundation construction irrespective of weather conditions and also become part of the regular construction scope.

The most critical challenge for any large size storage structures to be constructed on soft compressible soils is bearing capacity and consolidation settlements. Consolidation is the time-dependent phenomena, as expulsion of water from soil voids on application of external load will take longer period. It is mainly influenced by soil consistency, permeability, thickness of compressible stratum and presence of free-draining layers. This study deals with the foundation solution of a large size Mounded Storage Vessel (MSV) to be constructed on thick compressible stratum whose loading intensity is around 155 kPa, and the estimated settlements are greater than 400 mm. Hence, the foundation solution using vibro stone columns is adopted as an effective technique to address the challenges of excess settlements and inadequate bearing capacity. Further to keep settlements within the permissible limit of 50 mm, preloading technique with 60% of actual loading intensity will be utilized. The consolidation analysis of stone column-reinforced foundations is carried out based on the method given by Han and Ye (2001). The quality of the stone columns is ensured by real-time quality control measures, and the performance of the stone columns shall be ensured by vertical load tests following IS 15284-Part 1:2003. Ground settlements were closely monitored with proper instrumentations and the actual degree of consolidation has been verified by Asaoka (1978) method.

A Large Earth Cum Rock Fill, ECRF Dam, is under construction at Polavaram in the state of Andhra Pradesh in India as part of an irrigation project. The Embankment crest width of the dam is 12.5 m and the base width is approximately 136.75 m with a stepped sloping height of 27 m on both upstream/downstream sides. Once the 1.2 m Thick Plastic concrete cutoff wall is constructed below the dam along the longitudinal central axis to avoid seepage, this magnificent structure will be supported on a series of Deep Mixing Columns and Stone Columns that are evenly arranged under the footprint of ECRF Dam forming a smooth transition of gradually reducing stiffness moduli of treated ground from the centre of the embankment, where the foundation stresses are high, towards the edges in order to be able to progressively limit the settlements under the dam to a specified allowable limit. As such, the required post-treatment stiffness in the case of stone columns is 2 times the in situ stiffness of foundation soil, whereas it is expected to be 5 times the improvement for Deep Mixing as per project specifications. Laboratory testing and Field Trials were undertaken successfully to verify the design.

Ground Improvement Techniques serve to improve engineering properties for supporting various foundations. These may be undertaken either by conventional or advanced methods. The Controlled Modulus Column (CMC), also known as Rigid Inclusion, is a soil improvement technique to reduce the total and differential settlement by using semi-rigid soil reinforcement columns. The CMC technique can be executed by displacement or non-displacement methods. It does not aim to bypass the compressive layer or to instal a pile that will directly support the entire load from the structure. The principle of the technique is to introduce a load transfer platform between the head of the column and the structure, and transform a uniform load into the soil. Initially, the structural load transmitted into the soil generates a settlement greater than CMC piles. When the settlement between the soil and column became equal at the neutral point, the maximum structural load shall be balanced by the positive friction and tip resistance to stabilize the foundation without exceeding the allowable settlement limit. This paper describes the behaviour of soil reinforcement with CMC and their installation process with reference to a project at the Dry Bulk Terminal Port at Western coast of Africa. The methodology of CMC, requirements of Ground Improvement, arrangements and outcome of this method are presented in this paper.

The hilly regions of Kerala are severely affected by excess rainfall, causing tremendous damage due to landslides and slope failures. It is necessary to strengthen the existing slope profiles to prevent such disasters and avoid their risk to human lives and civil infrastructures. This paper studies the effect of micropile to reinforce the slopes in Idukki district of Kerala, where slope failures are frequent. Three-dimensional slope stability analysis is carried out on slopes from Idukki to obtain safety factor values using the MIDAS GTS NX program. The slope is fully saturated herein by taking the model's piezometric surface at the ground level to simulate high rainfall intensity. The critical slopes are then modelled with micropiles to analyze their effectiveness in improving stability under static conditions. Different micropile arrangements are considered, and a series of slope stability analyses have been carried out to obtain the optimum configuration with the required safety factor. The FOS values increased by more than 50% with micropiles for all the slopes. The optimum micropile arrangement obtained for each slope shows that micropile distribution between the toe and middle of the slope is an effective location for reinforcing slopes.

Soil liquefaction is a dangerous phenomenon that involves huge damages during strong earthquake ground motion events. Stone columns (SCs) are widely used as a liquefaction mitigation element which is expected to perform improvements against liquefaction hazard by densifying, increasing the stiffness and rapid dissipation of excess pore water pressure in the surrounding soil. Although in recent times, few studies on the behaviour of stone columns in the seismic zone have evolved, the performance of SCs in multi-layered soils is not been extensively examined. This paper presents the numerical investigations on the performance of SCs installed in multi-layered soils as a liquefaction mitigation measure against seismic loading. The acceleration time histories, Excess Porewater Pressure (EPP), vertical displacement and stress ratio were evaluated along different depths using PLAXIS 2D. With the installation of a stone column, there is a considerable reduction in the acceleration amplitude, which in turn reduces the EPP and vertical displacement at different locations and the amplitude of reduction depends on the soil stiffness levels at the depth.

Coastal cities are in desperate need of suitable land to meet the ever-increasing demand for urban infrastructure to support commercial, residential, tourism, and off-shore activities. Countries with a lengthy coastal line, such as India, possess significant areas of widespread highly saline soils subjected to periodic seawater intrusion. One such soil stratum was encountered in the Gulf of Cambay, Bhavnagar district, Gujarat, India. Due to the high volume of river runoff, the Gulf has a positive water balance. The relative humidity ranges from 65 to 86%, making the climate semi-arid to sub-humid. The high salinity, mineral content, basaltic origin, and deeper water table offered the impetus to investigate the applicability of various soil treatment options for such saline soils. Admixture stabilization techniques have been shown to help with problematic soil features. The Current study aims to determine the effectiveness of the addition of locally available lignite fly ash (10–30% by weight) and cement (6–9% by weight) to Bhavnagar saline soil in respect of strength, electrical conductivity, and CBR. In this assessment, a comparison of stabilized and unstabilized saline soil mixtures is expected to highlight the need of understanding the influence of treatment on the instinctive performance of stabilized saline soils, as well as assist practitioners in efficacious treatment of extreme saline soils for diverse geotechnical and construction applications.

Pile foundation is widely used in the construction of marine structures. In offshore and marine piling work, drilling/boring supporting fluid is used to stabilize the borehole (excavation) prior to tremie concrete. The poly-fluid is a synthetic drilling granular polymer mainly used for boring operations of deep foundations. Disposal of polymers after using them in the sea pollutes the sea environment, which may be harmful to living organisms inside the sea. In this study, an attempt is made to review the methodology and tests conducted on recycled supporting fluid to provide economic and environmental solutions during pile boring operation. First, the selection of supporting fluid confirming desired characteristics is done. Thereafter fluid is utilized for boring operations. Moreover, the used slurry is reused by treating it with an additional dose of fresh material/polymers. The amount of fresh materials/polymer to be added can be decided based on (viscosity, density and pH value) test results. The quality of recycled fluid is checked based on obtained test results. After getting satisfactory results, it is reused and finally disposed of at suitable dumping places.

In a congested city or urban area, the so-called “lifeline of the city”, i.e., Gas, Electricity, telecommunication, as well as other utilities or facilities are supplied or transported underground through buried pipes or utility tunnels. Sometimes these buried pipes or utility tunnels are deep underground and interfere with the foundation of the new structure. It is highly probable that a pile foundation is placed near an existing underground buried pipe or utility tunnel and may influence its load bearing capacity. Hence, the estimation of reduced load bearing capacity of the pile foundation placed near the existing buried conduit or utility tunnel is a complex soil-buried structure interaction problem. It is further complicated owing to uncertainty in the estimation of geotechnical parameters of foundation soil due to measurement and testing errors, inherent soil variability, and model translation. Under such circumstances, load bearing capacity is best assessed in the probabilistic framework or through reliability analysis. The present study demonstrates how the concept of response surface method (RSM) in conjunction with Numerical Analysis and First Order Second Moment (FOSM) methods can be combined as per the reliability analysis. The study answers the following question “reliability in reduction in the load bearing capacity of a single pile placed near the existing underground pipe or utilities tunnel”. It is demonstrated that the approach provides first-hand action on the reduction in the load bearing capacity and then estimates the reliability of that estimation in terms of an index called the Reliability Index (β). Such preliminary investigation can be useful for advocating the detailed analysis as well as in the decision-making for relocation of pile foundation.

Choosing for the best option of pile foundations to overcome large lateral and uplift loads for the foundations in transmission line towers/offshore environment is still being a concern to achieve the required capacities but also by considering the suitability aspect in the environment. The objective of this paper is to review the methods that have been done for knowing the uplift resistance and lateral resistance of pedestal piles. Investigations by different methods such as experimental studies and numerical and analytical studies have been done by various researchers in order to evaluate the response of a belled pile. These methods are discussed in this paper and the comparison with straight shaft piles is based upon the test and analysis. The results indicated that the uplift resistance and lateral resistance were significantly increased with the adoption of belled piles than straight shaft piles.

The trench cutter technology (also known as hydro mill) is well-known for constructing diaphragm walls for complex retaining structures. This however is not the only purpose for which the technology can be used. The world demands much more than just retaining structures. For instance, the installation of groundwater barriers, named Cut-Off-Walls (COW), is a very common field of application. Such barriers are used for sealing dams or encapsulation of contaminated areas. Also, the system can be used to install barrettes for foundation purposes, which can be a good alternative to pile foundation systems. But there are more ideas, not only for the standard deep foundation demands. Recently, the technology could also satisfy the idea of using the trench cutter technique as bulk sampling equipment. Such kind of new ideas obviously also require the adaption of equipment and tools to facilitate corresponding demands. Some reference projects as well as developments and specific solutions will be described and a general outlook will be given, after the explanation of the installation process in general.

The most challenging scope of any bridge project in marine or intertidal zone is to construct sub-structures like well foundation, group pile, pile cap etc. Similarly, it also affects the marine environment/ecology to a great extent. Understanding the level of difficulties and aiding to provide an environment friendly solution, various options are analysed to overcome these and found monopile to be the best alternative in this context. Generally, the foundation type of any bridge constructed in river, marine or intertidal zone in India is preferred for group piles. For the first time, monopile is being accepted as the foundation of bridge in India at Mumbai Coastal Road Project. The diameters of the monopiles used in this project are 2.5 m and 3.2 m. Hence, the challenges involved in monopile construction and the experiences to overcome it are worth sharing. Here, a brief discussion on environmental and geological issues and the need of monopile as the foundation of bridge has been discussed. Furthermore, the monopile construction stages and confirmation of monopile capacity through different load tests have been elaborated.

Near the port city of Whitby in the north-east of England, Anglo American (AA) is setting up the deepest mine in the UK, which will have a depth of 1,500 m. The purpose of the project is to extract and transport polyhalite, both underground, and to market it globally. As part of the construction works, BAUER Technologies Ltd, the UK subsidiary of BAUER Spezialtiefbau GmbH, constructed three different shafts using the diaphragm wall technique, with depths of up to 120 m. In order to ensure the specified vertical tolerance of maximum 200 mm, several measurement methods were applied, and the results were documented in a 3D model. Complex de-sanding plant technology and specially developed polymer products were adopted to regenerate the trench supporting bentonite slurry.

Liquid storage tanks are usually located in nearshore or coastal regions with soil profiles containing thick layers of compressible soils. These storage tanks are usually of large diameter up to 90 m and carry high loads, and the tanks are supported by heavy deep foundations such as piles. These structures are subjected to huge lateral loads due to wind and earthquakes, and any damage to storage tanks with highly inflammable liquids leads to disastrous conditions. So, it is important that the top layer of soil (up to the fixity depth) should be strong enough to provide the required lateral load capacity to the pile. In a project for constructing LNG terminal in Odisha containing 2nos of 89 m diameter LNG storage tanks supported with pile foundation located near to coastal region, for improving the lateral capacity of existing soil, the top 3 m was replaced with compacted engineered fill (GSB). The site was a filled-up area with dredged soil from the seabed, the top 5–10 m were soft to medium stiff clay with SPT N less than 10. The lateral design load on pile was 534 kN under free head condition. Actual lateral capacity for the strata was around 200 kN under free head condition which was less than the required capacity as per structural requirements. Therefore, for improving the lateral capacity of pile the top 3 m soil is replaced with well compacted engineered fill (GSB) in layers of 150 mm and the capacity is proved by conducting initial and routine lateral load tests. This paper describes the properties of the engineered fill used and how the lateral load capacity of pile was improved to meet the design requirement.