At Cengrs, one of our core values is sharing of knowledge. Owing to our extensive experience in providing expert Geo-technical engineering services to the construction industry, we have over the years, gained significant knowledge about the key issues and challenges in this domain. To consolidate this valuable learning, we have established a Knowledge Centre, which primarily works on the theology of collating information & experiences, and disseminating it to interested organizations & individuals.

Through case studies and technical papers, our Knowledge Centre aims to serve as an excellent resource for anyone conducting Geo-technical activities. We strongly believe that this knowledge should be constantly refreshed and improved to provide companies with the required guidance & support for enhancing business processes and improving efficiency.

• 07-Oct-2003

  Geotechnics of Artesian Flow Case Study of River Shivganga, Nepal

  Sanjay Gupta & Ravi Sundaram

  Abstract: Geotechnical investigations done for the bridge across River Shivganga on the Kohalpur-Mahakali Highway in the Terai region of southwestern Nepal reveal the occurrence of multiple layers at different depths with artesian ground water flow. The concept for foundation design in such strata should consider three aspects – (a) bed boiling (quick condition) should not develop even if maximum scour occurs, (b) during construction, a minimum soil cushion thickness should be available between foundation level and strata with artesian flow, and (c) for long term stability, the bearing capacity at artesian level should be computed using effective stress principle. The application of these concepts to fix the founding levels for well foundations for the bridge is discussed

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• 05-Sep-2003

  Foundation Stabilization of the Janmabhoomi Temple at Mangarh

  Ravi Sundaram and Sanjay Gupta

  Synopsis: The Janmabhoomi Temple is planned as an elegant structure in granite stone blocks. The foundation block bearing at 3 m depth is a 5.4 m thick massive platform made of granite masonry. Review of the soil condition revealed that under the design loads, the total and differential settlement may be excessive. To stabilize the foundation system, confinement of the foundation block was done by providing a row of 400 mm diameter closely spaced piles all around the Garba Griha, and in the central Mandap portion. Ground improvement was done in the associated structures (small temples corridor) to strengthen the soils and to restrict settlement.

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• 25-Jun-2002

  Dynamic Properties of Delhi Silt from Field Investigations

  H. Rao, S.Gupta, S. Narasaiah and G.V. Ramana (2002)

  Abstract: \nAll the earthquake resistant design and analysis procedures require site-specific/local dynamic site characterization. Dynamic site characterization includes shear wave velocity profile with depth, modulus reduction curves and damping characteristics of local soils. These are very essential and basic parameters required to conduct local site response/seismic wave propagation studies that should be duly incorporated into any earthquake resistant deign/analysis. \n \nShear wave velocity profiling is not a routine geotechnical investigation activity, as very specialized methods like seismic reflection, refraction, seismic cross-hole, down-hole and steady state vibration tests which fall under the domain of geophysical methods, are required which are very time consuming and expensive. A rapid, inexpensive method of finding shear wave velocity profile at a site is Spectral Analysis of Surface Wave (SASW) method.

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• 03-Sep-2001

  Use of Electrical Resistivity Tests for Geotechnical Investigations for Bridges

  Ravi Sundaram & Sanjay Gupta

  Background Inforamtion : The Ministry of Surface Transport (MOST) specifications for major bridges states that geotechnical investigation must done at every pier and abutment location. The normal practice is to drill boreholes at every location to a depth of “1.5 to 2B” (where B = foundation width) below founding level. This is sometimes supplemented by static cone penetration tests.\n \nThe paper presents the use of electrical resistivity test as an investigation tool to supplement the borehole data. The technique is time saving and is particularly useful in the current scenario of fast track

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• 23-Feb-2001

  Behavior of Dune Sands of the Thar Desert Under Dynamic Loading

  Sanjay Gupta and Ravi Sundaram

  Abstract: Forced vibration test were conducted on concrete blocks for a power project in north-western Rajasthan (India). The site is in the Thar desert and has meta-stable aeolian sand deposits. At shallow depth, the amplitude versus frequency curves shows two peaks, suggesting that the soil structure was probably collapsing and settling under the dynamic load. Tests conducted on the deeper, relatively more stable soils confirm a good response to dynamic loads. The instability under static loading conditions is also highlighted and correlated to the dune morphology.

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• 13-Jan-2001

  Risk in Estimation of Ultimate Loads of Ash Fill By Model Tests

  Anurag Goyal, V.K. Sood

  Abstract: The paper presents the reliability of bearing capacity equations for calculating ultimate load with respect to Model Plate Load tests on ash fill at different depths. The advantage of conducting Model Tests is that the test parameters that influence the estimated value of ultimate load significantly can be controlled effectively. As there is serious problem of disposal of fly ash, this study is done on compacted ash fill with a view to use it in land filling and reclaimation of low lying areas. For this, an experimental program has been conducted to study the difference in the measured ultimate load by Model Plate Load Tests (MPLT) and bearing capacity equation. The results indicate that the bearing capacity equation over-estimates the actual value of bearing capacity for D/B ratio <0.5 and under-estimates the bearing capacity value for D/B Ratio >1.0.

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• 11-Jan-2001

  Correlating Borehole Data with Electrical Resistivity Test Results

  Ravi Sundaram and Sanjay Gupta

  Synopsis: The results of electrical resistivity tests have been analysed using the”inverse slope method” to interpret the electrical-litholog This has been compared to borehole data so as to assess the Stratigraphy Correlating the resistivity data with the borehole data can be used sa a quality check and also as a geotechnical investigation tool to assess Stratigraphy,particularly where borehole data is insufficient case studies from two project sites are presented to illustrate the methodology for identifying the strata using resistity information.

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• 24-May-2000

  Geotechnical Engineering Practice: Professionalism and The Law

  Sanjay Gupta and Ravi Sundaram

  Synopsis: The Practice of geotechnical engineering includes consultancy work as well as construction activities .The paper presents a discussion on what problems ail its practice administrstion and its consequences as well as remedial legal measures as per the Indian law. The need for professionalism is emphasized together with an outline of the steps taken by ISSMGE and IGS on professional practice issues and suggestions on statutory recognition to resolve the problems.

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• 05-May-2000

  Ensuring Modern Reliability Of Foundation Design Rough Geotechnical Investigation Techniques

  Ravi Sundaram, Sanjay Gupta

  Synopsis: Geotechnical engineering provides the vital input for design of foundations which is of paramount importance for reliability in the performance of civil engineering structures. The paper presents a discussion on how modern field investigation techniques and in-situ testing backed up by a through laboratory testing programme can revolutionize foundation design. A carefully planned and properly executed investigation can results in a greater degree of confidence in the design in addition to cost effectiveness.

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• 21-Apr-2000

  Implementation of Highway : Geotechnical Aspects

  Sanjay Gupta, Ravi Sundaram

  Synopsis: The metropolitan cities are facing problems of traffic and transportation (Gopal Ranjan 1996). Site investigation is the first crucial step in the design and construction of highways. A carefully planned and properly executed investigation can result in a greater degree of confidence in the design and realistic evaluation of highway performance in addition to cost effectiveness.

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• 23-Feb-2000

  Geotechnical Design Criteria for Foundations of Large Diameter Tanks

  Gopal Ranjan, Ravi Sundaram and Sanjay Gupta

  Synopsis: Large diameter steel tanks are commonly used to store large volumes of crude oil,petroleum etc.The paper reviews the geotechnical design criteria for the foundation system for such tanks.where tanks are planned to be installed in weak sud-doils,this forms the basis for assessment of the need for ground inprovment. The concepts for the analysis based on the bearing capacity and settlement criteria are escussed in detail together with the stability of the tank during earthquakes.A need for standardizing hydratest procedures is emphasized.\n\nA case study illustrating foundation strengthening by provision of granular piles to improve loose subsoil to support a 22 m diameter tank is presented the field control methods for successful ground improvement are also discussed.

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• 25-Jun-1999

  Pile Foundations for Flyover (ROB) in Jaipur - Geotechnical Aspects

  Sanjay Gupta and Ravi Sundaram

  Synopsis: This paper presents the field experience of the authors in installing and testing diameter piles for an important projrct in the infrastructure sector in jaipur.Results of a geotechnical investigation conducted at the site are presented in conjunction with the results of load tests on initial and working piles.Load test results have been extrapolated using a hyperbolic model to assess the safe working load.

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• 21-Apr-1999

  Foundations for Large Diameter Tanks : Case Studies

  Gopal Ranjan, Sanjay Gupta and Ravi Sundaram

  The paper reviews the Geo technical design criteria for the foundation system of large diameter tanks used to store crude oil, petroleum products etc. Where tanks are planned to be installed in weak sub-soils, this forms the basis for assessment of the need for ground improvement. The concepts for the analysis based on the bearing capacity and settlement criteria are discussed in detail together with the stability of the tanks during earthquakes. A need for standardizing hydro test procedures is emphasized.

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• 22-Apr-1998

  Deep Foundations Under Artesian Conditions

  Sanjay Gupta and Ravi Sundaram

  Synopsis: Geotechnical investigations done at sites of bridges along the route of the kohalpur-Mahakali Highway in the terai region of western Nepal revealed the occuyyence of artesian groundwater flow in granular strata confined between clay layers.The paper discusses the methodology adopted for the geotechnical investigations.The concept for foundation design in such strata should consider three aspects-(a) bed boilong (quick condition) should not develop even after scouring, (b) during construction, minimum soil cushion thickness should be available above the artesian layer so that the artesian pressure does not puncture through, and (c) for long term stability, the bearing capacity at artesian level should be calculated using the effective overburden pressure.

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• 29-Jun-1997

  Dynamic Response of Hard Clays of the Pir Panjal Trap

  Sanjay Gupta, Ravi Sundaram, V.D. Miglani

  Synopsis: Forced vibration tests were conducted as per IS:5249 in conjunction with repeated triaxial tests at a site in Pampore (Jammu & Kashmir). The soils at the site consist of hard over-consolidated desiccated silty clays of the Pir Panjal Trap. The test results indicate a very good dynamic response and also an increase in dynamic soil parameters with depth. Values of coefficient of uniform elastic compression, coefficient of uniform elastic shear and dynamic shear modulus measured from the field tests, as well as the laboratory tests are reported here to illustrate the dynamic response of the hard silty clays of the Pir Panjal Trap.

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• 15-Jun-1997

  Cement Grouting in Delhi Silt - A Field Study

  Sanjay Gupta, Ravi Sundaram, T. Ramamurthy & S.N. Sinha

  Loose alluvial silts of delhi can be successfully grouted using cement slurry.The paper presents a case study wherein the cement grouting was done tostrengthen the foundations of a three storeyed building bearing on loose “Delhi Silt”. Details of the pressure grouting are presented together with the consumptions at vatious intake points. After grouting. The building was load tested to confirm the efficacy of theground improvement

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• 08-Apr-1996

  Gravel Piles: Construction and Field Testing

  Sanjay Gupta and Ravi Sundaram

  Abstract: Construction methodology for installation of gravel piles by the non-displacement technique (i.e. boring method) is discussed in the paper. Two case studies are also presented. The first one illustrates successful application in loose sandy strata at a site in the Indo-Genetic Alluvium. At this site, 400 mm dia stone columns were used to improve the soil beneath 22 m dia tanks. Load tests using different spacing between trial stone columns was used to optimize the design. The second case study relates to stone columns installed in marine clay in coastal Andhra Pradesh.

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• 25-May-1995

  Dynamic Characteristics of Collapsible Aeolian Sands

  Ravi Sundaram and Sanjay Gupta

  Synopsis: Forced vibration tests were conducted as per IS 5249 at a site in north-western Rajasthan. The soil at the site are meta-stable aeolian sands, piled up in the form of sand dunes. The test results indicate that, at shallow depths, in the loose to medium dense sands which are in the unstable part of the dune, the response under dynamic loading is poor. The two peaks in the amplitude-versus frequency curve suggest that the soil structure was probably collapsing and the sands were re-arranging into a more compact state. Tests were also conducted on the deeper relatively more stable soils. The test results were effectively used to design dynamically loaded foundations.

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• 26-Jun-1994

  Small Diameter Rammed Stone Columns in Fine Sands

  Ravi Sundaram and Sanjay Gupta

  Synopsis: The advantage of small diameter rammed stone columns is that they can be installed using simple augers and a small compaction winch. Thus rammed stone columns may be often work out as a cheaper alternative to pile foundations. It can cause substantial reduction in foundation settlement, thus making it an effective ground improvement technique.\n \nThe paper illustrates use of the technique for improving performance of foundations on loose alluvial sand. Case studies from two sites are presented where in the sand to about 3 to 5m depth were loose in condition; hence the allowable bearing pressure for the specified settlement was very low. Rammed stone columns of 300 mm diameter and 5 to 6m length were installed which successfully improved the allowable bearing pressure for open foundations by reducing settlement. Plate load test using 1m square test plate have been used to demonstrate the efficacy of the method. The spacing between the stone columns can be adjusted and optim

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• 02-May-1994

  Pile Foundations Save Transmission Towers at Agra

  Sanjay Gupta & Ravi Sundaram

  Abstract: The shfting of course of the Yamuna River at Agra by over 800 m during the last four years had threatedned the stabililty of transmission towers of a 220 KV - transmission line on the river bank. After last year\'s monsoons, the river had shifted dangerously close to the existing towers.\n \nCengrs Geotechnica Pvt. Ltd. was awarded the design and construction contract for providing deep pile foundations for the towers that extended below the level of maximum scour. In order to ensure minimum disruption of poer supply, the new towers were first installed and then charged, after which teh existing towers were dismantlled.

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