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vulcanhammer.net is pleased to feature papers by Dr. Mark R. Svinkin of Cleveland, OH. Dr. Svinkin is well known for his works on the vibrations of foundations, pile dynamics and other subjects of interest to the geotechnical community. Below is a list of his works on this site along with the abstracts. Click on the title to read the paper.
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Reliability of dynamic methods for determination of pile capacity is particularly important for piles driven in soils with time-dependent properties. This paper shows the advantages of the dynamic capacity methods and points out the necessity of considering the time effect for correct assessment of the accuracy of dynamic methods. The prediction of pile capacity in pre-driving wave equation analysis can be improved by the use of variable damping as a function of time. Pile capacity obtained from a static loading test cannot be accepted as a unique standard because the static loading test yields the pile capacity at the time of test only, due to the consolidation phenomenon. Dynamic capacity testing has this same limitation. Any comparison of static and dynamic tests has to be made for tests performed within a short duration. |
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The purpose of this paper is to present an overview of the existing criteria of ground vibrations generated by blasting. It is shown that these criteria have limited liability because they were found for specific categories of structures. A new approach is suggested for assessment of the damage in structures on the basis of measurement of structure vibrations that provides the flexibility of implicitly considering a variety of soil-structure interaction and structure conditions. It is explained the new frequency-independent safe level criterion that has to be chosen as 51 mm/s (2 in/s) for the PPV of structural vibrations. Attention is brought to seismographs with properly obtained calibration curves that have to be used for vibration measurements. Positive flexibility is demonstrated in assessment of structure and component of concern vibrations from blasting. |
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During the past three decades, dynamic methods became widespread technique for evaluation of the static pile capacity at the time of testing. High-strain dynamic pile testing and Statnamic tests have a substantial advantage of much lower cost and time. Determination of pile capacity from field testing is the primary application of the dynamic methods, but the accuracy and the area of utilization (soil conditions and pile type) of these methods are vague. Different hardware and software produce substantially diverse pile capacities. Hardware and software cannot resolve themselves the engineering problem of pile capacity determination by dynamic methods. Uncertainties are available in signal matching technique and comparison of the results of static and dynamic tests. Quality of dynamic measurements together with the software features and the engineering factors affect pile capacity obtained by dynamic testing. A simple practical approach is proposed for a proper choice of dynamic pile test at a specified construction site. |
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The application of dynamic methods to driven piles has advantages in evaluation of the hammer-pile-soil system and in data acquisition during pile driving and restrikes. Therefore during the last twenty five years, dynamic methods have become an integral part of pile capacity prediction and measurement for numerous projects. Dynamic methods use good quality hardware and software, but such great tools cannot themselves solve geotechnical problems of piling without engineering judgment. This paper shows some engineering assessments of determining pile capacity by dynamic formulas, wave equation analysis and dynamic testing. |
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Construction operations with involvement of impact or vibratory sources produce environmental vibrations for adjacent and remote structures. High vibrations and unacceptable dynamic settlements could seriously disturb sensitive devices and people and even be the cause of structural damage. Each construction site is unique and requires consideration of specific conditions at the site for decreasing vibration effects of construction activities on surrounding structures. Monitoring and control of ground and structural vibrations provide the rationale to select measures for prevention or mitigation of vibration problems. |
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Pile driving generates ground and structural vibrations which may detrimentally affect adjacent and remote buildings, houses, people and sensitive devices. Vibration effects on structures depend on numerous factors. Because of uncertainties in the vibration limits available for pile driving operations, condition surveys are very useful for analysis of the causes of the existing damage to structures. Surveys of structures should be performed before, during, and after pile installation. In general, condition surveys can be more important for the safety of structures than calculations of expected ground vibrations and vibration monitoring. Therefore, condition surveys have to be used together with vibration monitoring and control. Mitigation measure should be determined at the time of preconstruction condition surveys of structures. |
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Numerical methods are presented to predict complete vibration response of the soil, buildings or sensitive instruments caused by anticipated, future vibration sources such as construction or heave industry. The suggested methods make use of either Duhamel's integral or Fourier transforms and experimental soil response. |
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A letter from Dr. Svinkin concerning dynamic methods and new proposals which challenge them. |
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Uncertainty in geological stratification can strongly affect the prediction of ground and structure vibrations from construction and industrial sources. This paper presents the application of the deterministic impulse response function concept to solve the geotechnical problem of prediction of ground and structure vibrations before installation of a vibration source. This approach employs experimental impulse response functions for the considered dynamic system. These functions reflect real behaviour of soil and structures without the investigation of soil and structure properties. Ways for determining dynamic loads applied to the ground from different dynamic sources are also shown. A procedure is presented to compute predicted ground and structure vibrations. Good correlation is found between predicted and measured records. |
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Elastic properties of cushion materials are used to determine elastic properties of composite hammer cushions. Equivalent stiffness of the composite hammer cushion depends mostly on the characteristics of soft cushion material and only the thickness of a soft material, not the total cushion thickness, should be taken for calculations. Equivalent modulus of elasticity of the composite hammer cushion depends on the modulus of elasticity of a soft material and a ratio of stiff to soft layers thicknesses. A change of soft and stiff layers thicknesses and their ratio may be used as a tool to increase force transmitted to the pile |
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Construction-induced vibrations may be detrimental to adjacent structures and sensitive electronics operating nearby. Construction vibration sources have a wide range of energy and velocity, as a function of time, transmitted on the ground. Analysis of existing methods for predicting ground and structure vibrations shows that empirical equations provide calculations only of amplitudes of vertical soil vibrations with insufficient accuracy. This paper presents the application of the impulse response function concept to solve the geotechnical problem of predicting ground and structure vibrations before installation of vibration sources. Impulse response functions reflect real behavior of soil and structures without the investigation of soil and structure properties. A procedure is presented to compute predicted ground and structure vibrations. Good agreement is found between predicted and measured records. |
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Knowledge of pile capacity over a long period of time after the end of initial driving is important for proper design, construction and estimation of the cost of pile foundations. In this paper, assessment of pile capacity as a function of time has been performed for cohesive soils. On the basis of an existing formula, a new relationship between pile capacity and time after pile installation has been derived. This relationship takes into account pile capacity at the end of driving and an actual time after pile installation. Derived results can be used as a guide for evaluation of long term capacity of piles in cohesive soils. |
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High-strain dynamic pile testing is an important tool for driveability analysis, but the major objective of dynamic testing is determination of pile capacity at the time of testing. This method is a convenient tool in the pile driving industry. However, though high-strain dynamic pile testing has been used in practice for years, the actual accuracy and the area of application of this method, and also understanding the results of dynamic pile testing are vague. The paper presents discrepancies in highstrain dynamic pile testing, some uncertainty in the CAPWAP signal matching, negligible effects of soil properties on the CAPWAP results, incorrect interpretation and misleading use of testing results. It is shown the necessity to use engineering principles for verification of high-strain dynamic pile testing. |
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Reliability of dynamic methods for determination of pile capacity is particularly important for piles driven in clayey soils. This paper shows the conditions for proper comparison of static load test and dynamic testing results, analyzes the causes of erroneous prediction of pile capacities computed by wave equation analysis, and demonstrates that application of a variable damping coefficient can improve the reliability of wave equation solutions. |
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Construction vibrations may be harmful to adjacent and remote structures, sensitive instruments and people. Construction vibration sources have a wide range of energy, displacement, velocity and acceleration transmitted on the ground. Effects of different dynamic sources and soil conditions on construction vibrations is analyzed. Consequences of construction vibrations are developed in various ways. It is important to assess intolerable vibrations before the beginning of construction activities. Guidelines for preconstruction survey are presented. Pre-construction survey and prediction of anticipated vibrations by IRFP method, monitoring and control of measured vibrations are important steps in preventing intolerable vibration effect. |
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