Deep Foundations for Infrastructure Development in India

Inhaltsverzeichnis

1. Frontmatter

2. Geotechnical Investigation, Testing, Instrumentation, Monitoring and Quality Management

   1. Frontmatter

   2. Advanced Geotechnical Investigation and Data Interpretation for Complex Underground Structures

      M. Kalaiselvi, Y. Kaushik Sarma, G. D. Raju

      Abstract

      In recent times, development of underground space for variety of purposes is becoming more viable alternative to surface facilities with an ultimate aim of conserving surface space for various reasons and for strategic purposes. However, construction of underground structures continues to be expensive, with project cost rising rapidly and often significantly exceeding the preconstruction estimate. One of the most desirable and optimistic ways to improve the economic feasibility of underground construction is adopting a proper and systematic geotechnical investigation process. As variation in geology plays a dominant role in cost, feasibility, safety, and behavior of underground structure, serious consideration has to be given for geotechnical investigation. As soon as the investigation data is obtained, it should be properly interpreted and evaluated to get a meaningful outcome for greater savings in cost and time through optimum design. The basic objective of this paper is to recommend guidelines for planning and executing an effective multiphase geotechnical investigation program with advanced methods depending on the complexity of project and timely interpretation of the investigation data. This paper highly emphasizes on deriving the stratigraphy, structural features, presence of water pockets, in situ stress condition, and strength parameters through field and laboratory investigations. From this study, geotechnical engineers are expected to achieve a great extent of understanding in interpretation of investigation data and collaborating inter-related geotechnical information to derive the key aforementioned inputs. As a result, this will help in designing adequate support system for the underground structures, eradicating the possibilities of overdesign.

   3. Performance of Stone Columns in Soft Clay—A Comparative Study of Bearing Capacity of Soil Estimated Using Code Method, Actual Field Load Tests, and Observations from Numerical Model—A Case Study

      V. S. Parameswaran, Venkata Krishnaiah Yeddala

      Abstract

      Assam cancer care foundation (ACCF) proposed the construction of hospitals and related facilities across 18 locations in the state of Assam, India. In this paper, study on performance of stone columns in soft clayey soils at Jorhat site, one among the 18 locations is discussed. At this site, ground improvement by vibro stone columns of 900 mm diameter were installed at spacing of 2.0 m C/C in square pattern up to a depth of 9 m below founding level by dry bottom feed vibro displacement method to improve the safe bearing capacity of in situ soil from 70 to 140 kPa to support hospital building, LINAC block, and service building, by method of reinforcing the ground as they provide increased bearing capacity and reduce the foundation settlements. Stone columns were designed based on guidelines given in IS 15284(Part-I)-2013. The reliability of any method can be justified based on their ability to predict safe bearing capacities. Design is validated by two initial field load tests (single and group column test) and three routine load tests (single column test) as per guidelines given in IS code. Results showed 20% higher than estimated safe bearing capacities. Numerical modeling was also performed using PLAXIS-2D program. Deformations and stability checked using software and results were compared with actual settlements estimated empirically along with the field load tests. Comparison of results shows theoretical, field load test results hold good with numerical analysis results.

   4. Use of Reliability-Based Approach to Determine Geotechnical Parameters of Soil Site

      Gurpreet S. Bhatia, G. Prabhakar

      Abstract

      Proper geotechnical investigation plays an important role in suitably addressing the geotechnical challenges faced during construction stages. However, improper investigations lead to shocking results both financially and technically. Some of the most important geotechnical investigation tests like the Standard Penetration Test (SPT), Pressure Meter Test (PMT), etc. which are very much important in determining the foundation parameters, require too much manual intervention. These factors govern the workmanship of geotechnical investigation and the results we obtain from them. This leads to uncertainty in the results of these investigations. Generally, a number of tests are conducted below a particular structure and their average results are used for the design of foundations or other underground utilities. Against the backdrop of the fact that there are no stringent guidelines on the extent of geotechnical investigations to be carried out below critical structures like defense facilities, nuclear facilities, etc., this method of averaging may lead to obnoxious results. The greatest drawback of this approach is that we are not using sufficient data to characterize the soil profile of any particular area. In case some more investigations are done in that area, the results may change drastically. In this paper reliability-based approach is used to estimate the parameters obtained from SPT and PMT. The probabilistic approach is used to estimate the 95 percentile values of parameters that become input for the design of underground structures or utilities. As uncertainty exists in the evaluation of these parameters due to improper investigations, it is appropriate to evaluate these parameters based on the probabilistic approach using the best fit probabilistic distribution curve. This approach helps in the conservative estimation of geotechnical parameters below any structure with minimal failure probability.

   5. Liner Piles Used as Support to Kentledge for Initial Compression Load Test

      Thomas John, B. Venugopal, A. Vetriselvan, M. Kumaran

      Abstract

      The initial pile load tests are conducted to ensure the geotechnical capacity of the pile in a particular site condition. Normally kentledge method is adopted for the compression pile load tests. In this method the entire kentledge load is loaded above secondary beams which are supported by concrete blocks above the Natural Ground Level. So, it is important to ensure the SBC (for shear and settlement) of the natural ground. In one of our projects initially it was decided to go with the kentledge system for the initial compression load test on a 56 m long 1200 mm diameter BCIS pile. The test load and total kentledge load were 2160t and 2700t, respectively. The soil strata mainly consisted of clay with a low SPT N value and a water table almost at ground level. It was suggested to replace top soil using a Granular Sub-base (GSB) with good compaction in order to avoid excessive settlement of concrete blocks placed to support the kentledge weight. When the kentledge loading started, even before reaching 10% of the total kentledge load, an excessive settlement on the GSB layer was observed. This paper describes the problems faced during the normal kentledge method and how it was overcome using the liner pile system for initial compression load tests in this particular site condition for a higher test load.

3. Ground Improvement Techniques

   1. Frontmatter

   2. Development of Design Charts for Sand Compaction Pile Method of Improvement for Loose to Medium Dense Sands

      N. Aarthi, G. R. Dodagoudar

      Abstract

      The improvement of soft clay deposits using stone columns is a well-established ground improvement technique in the western world. This technique has been well documented and has proper design codes for precise execution in the field. The sand compaction pile (SCP) method is a contemporary technique for stone columns and has limited literature related to the strength characteristics of the loose to medium dense sand deposits treated with SCP. The available studies on the SCPs installed in cohesionless deposits focused on the improvement by indirectly assessing the SPT-N values pre- and post-installation of the SCPs. The widespread implementation of the SCP technique in recent years has increased the need for a more direct evaluation of the improvement. Earlier studies in this regard have revealed that the available design solutions are based on the type of installation equipment, their working efficiency, and accumulated field data. However, it is found that there are no generic design codes for the direct estimation of the ultimate bearing capacity of the SCP improved cohesionless deposits. To meet the design requirement for the SCP treated ground, a series of experimental and numerical investigations are performed in the present study to arrive at a direct framework in the form of design charts based on the pressure-settlement response of the treated ground. The developed design charts give the ultimate bearing capacity (UBC) of the treated sand deposit for the known initial relative density (RD) of the deposit, spacing and diameter of the SCPs, size of the footing, and for the specified target unit weight required for the intended application. It is concluded that the design charts will be of preliminary use to the design engineers to directly evaluate the UBC of the SCP improved loose to medium dense cohesionless deposits as part of the SCP method of ground improvement. It is expected to have more field-scale experiments and in-depth analysis before implementing these charts for actual field execution.

   3. Ground Improvement Using Stone Columns to Mitigate Liquefaction, Reduce Settlements and to Increase Safe Bearing Capacity of In-Situ Soils—A Case Study

      Venkata Krishnaiah Yeddala, Sai Vivek Adari, Suresh Kumar Velugu

      Abstract

      Assam cancer care foundation (ACCF) proposed the construction of hospitals and related facilities across 18 locations in the state of Assam-India. Tezpur is one among the 18 locations of Assam with high seismic risk. The strata at the site are comprised of mostly fine silty sands of lower SPT- N values. The water table is also encountered and ranging from 1 to 2 m below EGL. Since the site lies in seismic zone V as per IS 1893, detailed liquefaction analysis is carried out for all five boreholes and indicates that soil is liquefiable and ground improvement is inevitable up to a depth of 15 m below existing ground level. To mitigate the liquefaction potential and enhance the seismic performance of the soil, ground improvement using stone columns by Wet top feed Vibro replacement method is proposed. Also, the differential settlements can be avoided effectively under the raft foundation with Vibro Stone Columns. In this paper, field test validation results such as pre and post-SPTs and ECPTs to access the extent of ground improvement, along with other information adopted in this project presented.

4. Piling and Deep Foundation Techniques

   1. Frontmatter

   2. A Study on the Evaluation of Pile Bearing Capacity Factor and Adhesion Factor in IS 2911

      Ashirbad Satapathy, Ramanand Shukla, Sanket Rawat, Ravi Kant Mittal

      Abstract

      Bearing capacity factor (N_q) and adhesion factor (α) are the key parameters for analysing the load carrying capacity of pile foundations embedded in cohesionless and cohesive soils, respectively. Numerous models are available in the form of charts or equations for the computation of these parameters and, hence, have been adopted by most of the international and national standards. Indian Standard for the Design and Construction of Concrete Pile Foundations, IS 2911 Part 1 (2010), also makes use of charts detailed in its Annexure B. However, the sources of these charts have not been specified clearly, making it difficult to back-refer to the actual models to assess their basis for resolving any critical scenarios encountered during design. The present study aims at acquiring a distinct understanding of the development of these charts in order to bring more clarity to the design process of pile foundations. The given charts have been compared with various models specified in the existing literature and international standards for the calculation of N_q and α for both driven and bored piles and, hence, the basis of Indian Standard charts has been identified. Moreover, it is evident that the use of these charts complicates the process of automation of analysis and design of pile foundations as well as the associated optimisation studies. Additionally, the manual entry of data especially, from the logarithmic graph of N_q, escalates the chances of error thus, making it a critical concern for design offices. Therefore, this paper also presents a non-linear regression model for N_q and α, developed using NCSS software for both driven and bored piles. Through multiple iterations, the value of coefficient of determination for N_q and α has been found to reach greater than 0.995. The developed equations can be simplistically used for both manual and automated analysis of pile foundations.

   3. How Choice of Foundation Can Alter the Fate of a Bridge Project—Three Case Studies

      Alok Bhowmick

      Abstract

      The most uncertain and challenging part of a bridge design and construction is the ‘Choice of foundation’. During the planning and conceptual design stage, it is extremely important to choose the right type of foundation. Wrong choice can lead to disaster for the project. This paper will present three interesting case studies of past bridge projects, to demonstrate how correct choice of foundation can help to meet the project commitments, while the wrong choice of foundation can lead to a huge delay in project completion, leading to time and cost overrun.

   4. Soil–Structure Interaction for a Tension Pile Pulled with Strand

      P. V. Chandramohan

      Abstract

      A unique tension pile where the pull is at a point a certain distance below the top of the pile. The pull is transferred by a cable consisting of high-tensile strands. The HDPE duct of the cable prevents bond between the strands and pile concrete in the upper portion. While soil friction on the pile will act downwards on the whole length, there is tension in the bottom portion of pile and there will be compression at the top portion.

5. Earth Retention and Deep Excavation Support

   1. Frontmatter

   2. Challenges of Earthen Cofferdam in Deep Excavations for Waterfront Structures, a Case Study

      P. V. Ramana, M. Balasubramani, K. Bairagi

      Abstract

      This paper is a case study of an earthen cofferdam, constructed for a deep excavation at intake location in River Aaundha, Maharashtra, India. A 12 m (39 ft) deep excavation was made to construct the intake well. The natural soil profile at this location is clay followed by rock. An earthen Cofferdam of a maximum height of 7 m (23 ft) was made around the periphery of the excavation. Cofferdam embankment and excavation slopes were analysed using the finite element software PLAXIS-2D. Clayey sand was proposed as a filling material during design, but clayey soil was used for the embankment formation during execution. The embankment was built up to 5 m in height in July 2017 and completely submerged due to monsoon. In February 2018, the embankment height was raised to 7 m (23 ft) by filling the soil over the existing submerged embankment. After a few days of completion of the Cofferdam, the inside slope of the embankment had started sliding due to continuous dewatering. The design and execution of deep excavation with earthen Cofferdam for waterfront structures are challenging. The selection of filling material for embankment formation and dewatering techniques plays a vital role in the safety and stability of the embankments. Although all the safety measures were taken during the design, execution challenges are unpredictable.

   3. Confined Space and Inner-City Projects—Future Challenge and Opportunity for Diaphragm Walling

      Franz-Werner Gerressen, Alexander Blatt

      Abstract

      Diaphragm walls are known as underground structural elements commonly used as retention systems for excavation pits and shafts and permanent foundation walls or elements. One can anticipate that global urbanization and increasing demands on environmental considerations will need to be accommodated in underground space in the future. These trends show an increasing requirement for diaphragm walling in even more complex conditions, especially in inner-city applications with limited space. Complex conditions in terms of space limitations, especially for inner-city jobsites, require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistics to ensure smooth production. Furthermore, one focus will be given to the QA/QC topics of the production process. Real-time installation control, data transfer and reporting systems become more and more important. Therefore, the paper will describe the construction method and the sequence of activities required for the construction of diaphragm wall systems. It will also describe the main equipment that will be needed to execute these works under various conditions. In addition to the general description of the system and the required equipment, the paper will show some site examples for infrastructure projects with their specific solutions when working under space restrictions.

   4. Effects of Change in the Support System on Temporary Secant Pile Wall

      C. Anburaj, A. Srinivas

      Abstract

      Deep excavation with a support system is required to construct various parts of underground structures like shafts, stations, entry structures, etc. These structures have to be constructed using permanent or temporary embedded retaining walls with a support system. The selection of a suitable type of retaining wall will depend upon the geological condition present in the particular location, time, cost, available equipment, etc. In Bangalore Metro Rail Project, a secant pile wall was adopted as the temporary earth retaining system with the depth of excavation of about 20 m. It was designed initially based on bottom-up construction methodology with 3 levels of struts and 3 levels of anchors, but at a later stage, due to time and other construction-related issues, it was decided to change the configuration to 6 levels of struts. Generally, in deep excavations, all the underground structures should be designed and checked for the critical forces from both permanent stage and construction stages. Since secant piles are used as a temporary retaining wall, only construction stage analysis is carried out to get the governing forces and deformation. In construction stage analysis, soil layers are defined with boundary conditions, and the surcharge during construction and surcharge from the actual building near the secant pile are considered. This paper discusses the effect of change in the support system from anchors to struts and how these changes in the support system affect the behaviour of the secant pile and subsequently adjacent buildings present in the influence zone of the excavation. As a result, in changing from anchors to struts, the wall displacement, strut forces and ground movement on the adjacent ground and buildings increase. The increase in deflection, ground movements and strut forces occurs during backfilling sequence of the underground station excavation. During backfilling, struts have to be removed and this imparts a higher magnitude in deflection, strut forces and ground movements.

   5. Overview of Enabling Works for Waterfront Structures—Design and Construction

      K. Raja Rajan, D. Nagarajan, T. Vijayakumar

      Abstract

      Major bridges crossing mighty rivers must be constructed in flowing water. Constructing the sub-structure in water has been a challenging job for the contractor. Special construction techniques with marine fleets are to be adopted for waterfront construction. Enabling works like temporary piling platforms and cofferdams are used for pile and pile cap construction. Apart from this, enabling works like load out jetty to transport the materials from land to water; temporary walkway for access of workman to work location; temporary access bridge for construction vehicles movement; temporary liners for tower crane foundation; Concrete block to act as dead man anchor for barge movements are all required by the contractor for smooth functioning of the site as per construction schedule. Investment in enabling works by the contractor plays a significant role in the profit margin of the project, and of course, with utmost safety. Design of enabling works for waterfront structures involves hydrological data like afflux, bathymetry survey, current force, scour depth, and wave force to be taken cautiously for safe and economic design. The type of foundation and pile/well cap top level corresponding to water levels influence the construction scheme. The usage of geotechnical software like Wallap and Plaxis required for enabling work design to enhance the safety of the structure. Bathymetry and soil condition play a critical role in the design and construction of enabling works. Water Discharge quantity in the river along with water levels like low-water level, high flood level, and seasonal fluctuation of water levels has a great impact on the design of enabling works. Establishing enabling works for waterfront construction near an existing bridge is an additional challenge for the contractor. Along with the design, constructing the enabling works in water requires a special construction methodology and sequence of work. This paper provides insights into the design and construction of enabling works for waterfront construction.

   6. Realistic Estimation of Water Table Depth for Design Optimisation of Bored Tunnel and Cut and Cover Structures for Underground Metro

      Chiranjib Sarkar, Sibapriya Mukherjee, NKumar Pitchumani

      Abstract

      With the rapid expansion of urban transportation systems, tunnels and cut & cover structures are considered as the only solution in improving the urban space congestion problem in mass rapid transit system. Therefore, it is necessary to accurately design underground structures with realistic assumptions and considerations of design parameters like site geotechnical data, water table, surcharge load, etc. Over-conservative approach provides not only uneconomical design but also frequently results in overdesign of the structures. Water table depth has a significant role in some design aspects of underground structures like floatation check, lateral and uplift pressure on the buried structure, etc. In the current practice of tunnel and cut & cover structure design, water table is assumed to coincide with the ground level. Most of the Design Basis Reports & Outline Design Specifications directly mention consideration of water table at ground level for floatation check and load calculations, etc. However, the actual scenario is different in most of the cities, especially in northern, central, western and eastern regions of India except the coastal cities. In the present study, an attempt has been made to carry out a parametric study on the effect of water table depth in the design of a typical 6.3 m outer diameter circular tunnel with a 6 m backfill. In this study, it is also attempted to establish an analytical method of calculating the most realistic consideration of water table depth instead of the present hypothetical assumption of considering water table to coincide with the ground level. The findings of the current study may be helpful to the researchers and practising engineers in the design of tunnel and cut & cover structure for subways and metros.

6. Research, Experimental and Numerical Methods in Deep Foundations and Deep Excavation Technologies

   1. Frontmatter

   2. Comparison of Ground Movement Near Buildings Due to Underground Station Excavation With Analytical and Numerical Methods

      A. Srinivas, C. Anburaj

      Abstract

      In urban areas, construction of underground stations and basements is always a challenging task due to the presence of dense sensitive buildings in the vicinity. The main objective of this paper is to predict the ground movements associated with construction phase of launching shaft excavation in Bangalore Metro project analytically. Also, the comparison of these predicted values with numerical values, and subsequently with actual measurements is presented. These values will help to assess the potential damage, both architecturally and structurally, to the existing building in the influence zone due to ground movements. The principles given by (Bowles JE (1990) Foundation analysis and design, 4th Edn. McGraw-Hill book company, New York, USA. Foundation Analysis and design. 4th Ed., McGraw-Hill book company, New York, USA.) and (Clough and O’Rourke, Specialty conference on Design and Performance of Earth Retaining structures, ASCE Special publication, No. 25:439–470, Clough GW, O’Rourke TD (1990) Construction induced movements of in-situ walls. In: Specialty conference on Design and Performance of Earth Retaining structures, vol. 25. ASCE Special publication, pp. 439-470) depending on the type of soil shall be used to compute ground movements of buildings present in the influence zone. Based on several case histories, (Clough and O’Rourke, Specialty conference on Design and Performance of Earth Retaining structures, ASCE Special publication, No. 25:439–470, Clough GW, O’Rourke TD (1990) Construction induced movements of in-situ walls. In: Specialty conference on Design and Performance of Earth Retaining structures, vol. 25. ASCE Special publication, pp. 439-470) suggested that the settlement profile is triangular for an excavation in sandy soil or stiff clay. The maximum ground surface settlement will occur just behind the wall. The influence zone of the corresponding settlement will extend about twice to thrice of the influence depth (H_e) for sandy soil and stiff to very hard clays, respectively. This paper compares ground movement of building predicted by above analytical method and numerical analysis carried out using PLAXIS 2D finite element software. The buildings that are in the influence zone of excavation are considered. On comparing the results obtained from numerical, analytical and actual settlement values, it is observed that wall deflection from numerical values is about 33% higher than actual value. In addition, the maximum ground settlement obtained from numerical analysis is comparable with the settlement obtained from analytical approach. However, the observed settlements at the building locations are significantly smaller than predicted. This might be due to support provided by the secant pile walls in the opposite side as the stress around the retaining wall will be in a three-dimensional direction. Also, the deep ground water table during the excavation could have helped in reducing the wall movement and the ground settlement.

   3. Numerical Study on Uplift Capacity of Helical Pile Embedded in Clay

      V. Karthick Kumar, M. Muttharam

      Abstract

      Helical piles foundation systems have been extensively used in engineering applications. It is commonly adopted to resist the compression, uplift force, overturning moment and lateral forces. Helical pile system is extensively used in many structures such as Transmission towers, Wind farms and other offshore structures because it is easy and quick to install. Realizing the importance of helical pile, an attempt is made in the present investigation to bring out the effect of spacing between the helix, blade thickness, and shaft thickness through numerical analysis. To validate the finite element model experimental investigation was carried out. In this investigation model steel piles with dual helical plate embedded in clay bed with the consistency of 0.4 was tested to study the effect of uplift loading on the behaviour of piles in tensions. Model helical pile with 12.5 mm diameter circular shaft and helix diameter of 25 mm. The model pile is embedded in clay bed for a depth of 400 mm. Parametric analysis of helical pile by varying blade thickness, shaft thickness, and the spacing of helix was carried out by using Finite Element tool Plaxis 3D. From this analysis, an increase in thickness from 4 to 10 mm increase the uplift load. Similarly, an increase in spacing of helices from 0.5  to 1.5 m increases the uplift capacity beyond that it decreases the uplift capacity. By keeping the contact area of the helix as constant as the number of a helix and helical spacing was varied, the critical number of the helix was found as 2 and the critical spacing of helix was found as 1.5 m for this study.

7. Safe and Efficient Geo-Construction

   1. Frontmatter

   2. Rectification Measures and Restoration of Distressed Pump Foundations

      Sampat Raj, Geethanjali Koppolu, V K Panwar

      Abstract

      At a Fertilizer plant located in the southern part of India, 74 numbers of pump foundations have shown non-uniform settlements causing the tilting of pump foundations under self-weight primarily due to the presence of varying thickness of the heterogeneous subsoil beneath the pump foundations and soil erosion because of water seepage through deeper excavations in the close vicinity. Various corrective measures have been explored and taking due cognizance of the prevailing subsoil conditions, site constraints, and constructability aspects, micropiling has been adopted. This paper presents the site problem and details of remedial measures adopted for rehabilitation of the distressed pump foundations. The main objective of this paper is to provide guidelines for designer during design and detail engineering stage to avoid similar nature of problems and also to provide a solution concept to tackle similar nature of problem(s) if encountered at the site.