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.
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.
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.
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.
Robert M. Ebeling and Ernest E. Morrison, Jr.
USAE Waterways Experiment Station Information Technology Laboratory Technical Report ITL-92-11
Naval Civil Engineering Laboratory NCEL TR-939
In addition to a complete description of seismic design aspects of retaining walls, this report has one of the best descriptions of lateral earth pressures available.
This technical report deals with the soil mechanics aspects of the design of waterfront retaining structures built to withstand the effects of earthquake loadings. It addresses the stability and movement of gravity retaining walls and anchored sheet pile walls, and the dynamic forces against the walls of drydocks and U-frame locks.
The effects of wall displacements, submergence, liquefaction potential, and excess pore water pressures, as well as inertial and hydrodynamic forces, are incorporated in the design procedures. Several new computational procedures are described in this report. The procedures used to calculate the dynamic earth pressures acting on retaining structures consider the magnitude of wall displacements.
For example, dynamic active earth pressures are computed for walls that retain yielding backfills, i.e., backfills that undergo sufficient displacements during seismic events to mobilize fully the shear resistance of the soil. For smaller wall movements , the shear resistance of the soil is not fully mobilized and the dynamic earth pressures acting on those walls are greater because the soil comprising the backfill does not yield, i.e., a nonyielding backfill.
Procedures for incorporating the effects of submergence within the earth pressure computations, including consideration of excess pore water pressures, are described.
15 November 1997
Supersedes NAVFAC DM 7.3, April 1983
- BASIC DYNAMICS
- Vibratory Motions
- Mass, Stiffness, Damping
- Amplification Function
- Earthquake Ground Motions
- SOIL PROPERTIES
- Soil Properties for Dynamic Loading
- Types of Soils
- Dry and Partially Saturated Cohesionless Soils
- Saturated Cohesionless Soils
- Saturated Cohesive Soils
- Partially Saturated Cohesive Soils
- Measuring Dynamic Soil Properties
- Field Measurements of Dynamic Modulus
- Laboratory Measurement of Dynamic Soil Properties
- MACHINE FOUNDATIONS
- Analysis of Foundation Vibration
- Machine Foundations
- Impact Loadings
- Characteristics of Oscillating Loads
- Method of Analysis
- Dynamic Soil Properties Design to Avoid Resonance
- High-Speed Machinery
- Low-Speed Machinery
- Coupled Vibrations
- Effect of Embedment
- Proximity of a Rigid Layer
- Vibration for Pile Supported Machine
- Foundation Bearing Capacity and Settlements Vibration Transmission, Isolation, and Monitoring
- Vibration Transmission
- Vibration and Shock Isolation
- Vibration Monitoring
- DYNAMIC AND VIBRATORY COMPACTION
- Soil Densification
- Dynamic Compaction Applications of Vibroflotation
- Compaction Grout
- PILE DRIVING RESPONSE
- Wave Equation Analysis
- Wave Propagation in Piles
- Wave Equation Application
- Dynamic Testing of Piles
- Results From Dynamic Testing
- Pile Dynamic Measurement Applications
- Apparatus for Applying Impact Force
- Impact Force Application
- Apparatus for Obtaining Dynamic Measurement
- Signal Transmission
- Apparatus for Recording, Reducing, and Displaying Data
- EARTHQUAKE, WAVES, AND RESPONSE SPECTRA
- Earthquake Mechanisms
- Wave Propagation
- The Response Spectrum
- SITE SEISMICITY
- Site Seismicity Study
- Ground Motion Estimates Analysis Techniques
- SEISMIC SOIL RESPONSE
- Seismic Response of Horizontally Layered Soil Deposits
- Evaluation Procedure Analysis Using Computer Program
- DESIGN EARTHQUAKE
- Design Parameters
- Factors Affecting Ground Motion
- Ground Motion Parameters
- Site Specific Studies
- Earthquake Magnitude
- Design Earthquake Magnitude
- Selection of Design Earthquake
- Intensity Peak
- Horizontal Ground Acceleration
- Seismic Coefficients
- Magnitude and Intensity Relationships
- Reduction of Foundation Vulnerability to Seismic Loads
- SEISMIC LOADS ON STRUCTURES
- Earthquake Induced Loads
- Foundation Loads
- Wall Loads
- Base Shear
- LIQUEFACTION AND LATERAL SPREADING
- Liquefaction Considerations
- Factors Affecting Liquefaction
- Evaluation of Liquefaction Potential
- Simplified Empirical Methods
- Peak Horizontal Acceleration
- Laboratory Tests and Site Response
- Method Slopes
- Pseudostatic Design
- Strain Potential Design
- Lateral Spreading From Liquefaction
- Lateral Deformation
- Evaluation Procedure
- FOUNDATION BASE ISOLATION
- Seismic Isolation Systems
- System Definitions
- Passive Control Systems
- Active Control Systems
- Hybrid Control Systems
- Mechanical Engineering Applications
- Historical Overview of Building Applications
- Design Concept
- Device Description
- Elastometer Systems
- Sliding System
- Hybrid Systems
- Examples of Applications
SPECIAL DESIGN ASPECTS
- SEISMIC DESIGN OF ANCHORED SHEET PILE WALLS
- Design of Sheet Pile Walls for Earthquake
- Design Procedures
- Example Computation
- Anchorage System
- Ground Anchors
- Displacement of Sheet Pile Walls
- STONE COLUMNS AND DISPLACEMENT PILES
- Installation of Stone Columns
- Parameters Affecting Design Consideration
- Soil Density
- Coefficient of Permeability
- Coefficient of Volume Compressibility
- Selection of Gravel Material
- Vibro-Replacement (Stone Columns)
- Vibroflotation and Vibro-Replacement
- DYNAMIC SLOPE STABILITY AND DEFORMATIONS
- Slope Stability Under Seismic Loading
- Seismically Induced Displacement
- Slopes Vulnerable to Earthquakes
- Deformation Prediction From Acceleration Data
- Computation Method
- Sliding Rock
University of Delft, The Netherlands
Also available: Software for Soil Dynamics (zip format, Windows)
A complete treatment on this subject, whose coverage in the literature is woefully inadequate. Topics include the following:
- Vibrating Systems
- Theory of Consolidation
- Plane Waves in Porous Media
- Waves in Piles
- Earthquakes in Soft Layers
- Cylindrical Waves
- Spherical Waves
- Elastostatics of a Half Space
- Elastodynamics of a Half Space
- Foundation Vibrations
- Moving Loads on an Elastic Half Plane
High-strain dynamic pile testing is an important tool for drivability 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 high-strain 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.
Linda Al Atik and Nicholas Sitar
Department of Civil and Environmental Engineering
University of California, Berkeley
PEER Report 2007/06
Two sets of dynamic centrifuge model experiments were performed to evaluate the magnitude and distribution of seismically induced lateral earth pressures on retaining structures that are representative of designs currently under consideration by the Bay Area Rapid Transit (BART) and the Valley Transportation Authority (VTA). Two U-shaped cantilever retaining structures, one flexible and one stiff, were used to model the prototype structures, and dry medium-dense sand at 61% and 72% relative density was used as backfill.
The results of the centrifuge experiments show that the maximum dynamic earth pressure increases with depth and can be reasonably approximated by a triangular distribution analogous to that used to represent static earth pressure. In general, the magnitude of the seismic earth pressure depends on the magnitude and intensity of shaking, the density of the backfill soil, and the flexibility of the retaining walls. The resulting relationship between the seismic earth pressure coefficient increment (!KAE) and PGA suggests that seismic earth pressures can be neglected at accelerations below 0.3 g. This is consistent with the observations and analyses performed by Clough and Fragaszy (1977) and Fragaszy and Clough (1980), who concluded that conventionally designed cantilever walls with granular backfill could reasonably be expected to resist seismic loads at accelerations up to 0.5 g.
Conventional seismic design procedures based on the Mononobe and Okabe work that are currently in use were found to provide conservative estimates of the seismic earth pressures and the resulting dynamic moments. Specifically, the BART design criterion for rigid walls appears amply conservative, especially if the normal factors of safety are taken into account. The BART design criterion for flexible walls appears to be somewhat unconservative for loose backfill. However, considering the various factors of safety present in the conventional design it may in fact contain an appropriate level of conservatism. An important contribution to the overall moment acting on the wall is the mass of the wall itself. The data from the centrifuge experiments suggest that this contribution may be as much as 25%.
Given that the conventional analyses methods tend to give adequately conservative results without the separate consideration of the wall inertial effects, the contribution of seismic earth pressures to the overall moment acting on the retaining structures is apparently routinely overestimated. Further analyses are needed to fully evaluate the impact of this observation on the overall design.
Larry D. Olson, P.E.
This research project was funded to investigate the possibility that, by measuring and modelling the dynamic response characteristics of a bridge substructure, it might be possible to determine the condition and safety of the substructure and identify its foundation type (shallow or deep). Determination of bridge foundation conditions with this approach may be applied to quantify losses in foundation stiffness caused by earthquakes, scour, and impact events. Identification of bridge foundation type may be employed to estimate bridge stability and vulnerability under dead and live load ratings, particularly for unknown bridge foundations.
Effects of Void Redistribution on Liquefaction-Induced Ground Deformations in Earthquakes: A Numerical Investigation
University of British Columbia (Vancouver)
Liquefaction-induced ground failure continues to be a major component of earthquake related damages in many parts of the world. Experience from past earthquakes indicates lateral spreads and flow slides have been widespread in saturated granular soils in coastal and river areas. Movements may exceed several meters even in very gentle slopes. More interestingly, failures have occurred not only during, but also after earthquake shaking.
The mechanism involved in large lateral displacements is still poorly understood. Sand deposits often comprise of low permeability sub-layers e.g., silt seams. Such layers form a hydraulic barrier to upward flow of water associated with earthquake-induced pore pressures. This impedance of flow path results in an increase of soil skeleton volume (or void ratio) beneath the barrier. The void redistribution mechanism as the focus of this study explains why residual strengths from failed case histories are generally much lower than that of laboratory data based on undrained condition.
A numerical stress-flow coupled procedure based on an effective stress approach has been utilized to investigate void redistribution effects on the seismic behaviour of gentle sandy slopes. This study showed that an expansion zone develops at the base of barrier layers in stratified deposits subjected to cyclic loading that can greatly reduce shear strength and results in large deformations. This mechanism can lead to a steady state condition within a thin zone beneath the barrier causing flow slide when a threshold expansion occurs in that zone. It was found that contraction and expansion, respectively at lower parts and upper parts of a liquefiable slope with a barrier layer is a characteristic feature of seismic behaviour of such deposits. A key factor is the pattern of deformations localized at the barrier base, and magnitude that takes place with some delay. In this thesis, a framework for understanding the mechanism of large deformations, and a practical approach for numerical modelling of flow slides are presented.
The study was extended to investigate factors affecting the seismic response of slopes, including: layer thickness, barrier depth and thickness, ground inclination, permeability contrast, base motion characteristics and soil consistency.
Another finding of this study was that a partial saturation condition results in delay in excess pore pressure rise, and this factor may be responsible for the controversial behaviour of the Wildlife Liquefaction Array, California (USA) during the 1987 Superstition earthquake.
It was demonstrated that seismic drains are a promising measure to mitigate the possible devastating effects of barrier layers.
Colin Gordon & Associates, San Mateo, California USA
Vibration analyses of advanced technology facilities typically must consider frequency as well as amplitude of vibration. A soil propagation model is proposed which will allow the use of site-specific, measurable, frequency dependent attenuation characteristics. A method is given which allows in-situ determination of those frequency-dependent properties. This approach is applied to the estimation of setback distances for various items of construction equipment at a particular site.
This document has been written to provide information on how to apply principles of geotechnical earthquake engineering to planning, design and retrofit of highway facilities. Geotechnical earthquake engineering topics discussed in this document include:
- deterministic and probabilistic seismic hazard assessment;
- evaluation of design ground motions;
- seismic and site response analyses;
- evaluation of liquefaction potential and seismic settlements;
- seismic slope stability and deformation analyses; and
- seismic design of foundations and retaining structures.
This document provides detailed information on basic principles and analyses, with reference to where detailed information on these analyses can be obtained.
This document presents a series of five design examples illustrating the principles and methods of geotechnical earthquake engineering and seismic design for highway facilities. The examples presented in this volume cover a wide range of problems encountered in geotechnical earthquake engineering practice. The design examples presented in this document include:
- seismic design of a shallow bridge foundation;
- seismic design of a driven pile bridge foundation;
- seismic design of a gravity retaining wall based on results of a detailed seismic hazard analysis;
- seismic slope stability analysis of a cut slope in soft rock; and
- liquefaction potential analysis.
Richard Lane and Krystle Pelham
New Hampshire Department of Transportation
8 September 2012
The recent trend in highway construction within New Hampshire has been toward reconstruction and rehabilitation projects in congested urban areas. This has resulted in a greater concern for vibrations generated by non-blasting construction activities, a greater potential for complaints, increased potential for damage, and increased need to monitor vibrations during the construction phase of projects. A procedure for assessing the potential impact of non-blasting construction-induced vibrations at a project site has been modeled after the “Rock Fall Hazard Rating System” as published in the Federal Highway Administration’s “Rock Slopes Reference Manual” (FHWA HI-99-007). An impact assessment of construction vibrations can consider each type of vibration producing activity and the potential impact that activity would have on man-made structures and/or vibration sensitive equipment that is in relevant proximity to the project site. A “Construction Vibration Impact Assessment Table” was developed, providing a means of rating the potential impact of a specific construction activity at a given site. This rating will allow comparison of a specific construction activity at different sites, or different construction activities at the same site. The “Construction Vibration Database” was created as part of this research project, with the intent of providing a means of recording information on various types of non-blasting construction vibration activities. It is intended that this database will be continually updated with data submitted by both in-house resources and by vibration consultant subcontractors working on NHDOT projects. This database will provide designers with a means of accessing empirical data to be used for forecasting expected vibration impacts on upcoming construction projects. The “Construction Vibration Assessment Procedure” and “Construction Vibration Database” can be used to develop a preliminary cost estimate for vibration monitoring services and as a resource for decision-making during the design and construction phases of NHDOT projects. Information was collected on a variety of non-blasting construction activities to include vibratory compaction, excavation, splitting of rock with a hoe-ram, sheet pile driving, pavement breaking, demolition, track mounted vehicles and heavy construction traffic at various project sites throughout the state.
Mohammed Massoud Ramadan
M.Sc. Thesis, Tanta University
The development in construction field has increased with high rate in the last decades; many modern ways are started to be used to make the construction process easier than before. This thesis is focusing on two methods of construction in geotechnical field and they are pile driving and dynamic compaction. Both techniques produce high magnitude of vibration through soil due to the large amount of energy which is used in driving or compaction. Vibrations are generated in large values and propagate quite fast and affect many wide areas around the vibration source.
Those vibrations may have a very destructive effect on the adjacent structures and the heritage buildings or even the underground facilities. The damage occurs due to two reasons, soil settlement beneath foundation or the directly vibrations on the building. PPV (peak particle velocity) is considered the main indicator for the possible damage which may happens to the structures, therefore, a lot of parameters and their effect on PPV are studied in this thesis. Soil settlement is a very dangerous problem facing engineers when they have a vibration source such as pile driving or dynamic compaction , the available models for evaluating settlement values due to vibrations are also investigated.
In addition different of wave barriers as a way of preventing wave’s propagation and protecting the adjacent structures close to the vibration source are investigated in details.
Robert M. Ebeling
U.S. Army Corps of Engineers
Technical Report ITL-92-4
This technical report presents an introduction to the computation of a linear response spectrum for earthquake loading and defines the terms associated with response spectra. A response spectrum is a graphical relationship of maximum values of acceleration, velocity, and/or displacement response of an infinite series of elastic single degree of freedom (SDOF) systems subjected to time dependent dynamic excitation.
This report reviews the formulation and solution of the equation of motion for a damped linear SDOF system subjected to time dependent dynamic excitation. Due to the irregular nature of the acceleration time histories that have been recorded during earthquakes, numerical methods are used to compute the response of SDOF systems during the course of developing response spectra. The fundamentals of the solution of the equation of motion for SDOF systems are also described.
R. Scott Ganin, P.E.
Alaska Dept. of Transportation & Public Facilities
This paper introduces the physics and analysis of wave propagation in pavement and soils. The study of wave propagation in soils can yield useful results to engineers concerned with the resilient characteristics of a particular site, dynamic soil-structure interaction (e.g., pavements or soils), and earthquake analysis. Types of waves considered here are those resulting from forced impulses and ground penetrating radar. Background of the development in measuring waves in soils beginning in the late 1930’s to the present is given. Practical and useful applications are presented along with equipment necessary to obtain results. Use of wave measuring equipment may expedite soil exploration in the future.
Gregg L. Fiegel and Bruce L. Kutter
Naval Civil Engineering Laboratory CR 92.009
Results from six centrifuge model tests are presented. Four of the model tests involve layered soil deposits subject to base shaking; two model tests involve uniform soil deposits of sand subject to base shaking. The layered soil models consisted of a saturated liquefiable fine sand overlain by a layer of relatively impermeable silica flour (silt). Pore water pressures, accelerations, and settlements were measured during all six tests. Results from the model tests involving layered soils suggest that during liquefaction, a water interlayer or very loose zone of soil develops between the sand and the silt due to the difference in permeabilities. Soil volcanoes or boils were seen on the surface for all four of these layered model tests. The locations of these boils, in each test, were found concentrated in the weakest zones of the over-lying silt layer; cracking of the weak silt zones provided a release or a vent for the excess pore water pressure generated as a result of particle rearrangement in the liquefiable fine sand.
Brent R. Robinson
North Carolina State University
This study compares high strain dynamic testing measurements taken near the top of a driven pile to peak particle velocities on the ground surface and sound levels detected in the air some distance from the pile during driving. Based on a sample of installation records from 16 piles driven at the Marquette Interchange Project in Milwaukee, Wisconsin, a series of peak particle velocity plots versus distance, energy and scaled distance were created using traditional horizontal distance and rated hammer energy. These plots were modified using the seismic distance, the diesel hammer potential energy from the calculated stroke, and the energy transferred to the pile top. Incorporating these measurements tended to reduce some of the scatter in the data. More importantly, it was also discovered that components of peak particle velocity in the ground can be well correlated to the total pile resistance measured by dynamic testing. A plot of total resistance versus depth often independently yields the same shape curve as a plot of at least one component of peak particle velocity versus depth. A simple mathematical attenuation model is proposed as an initial step toward utilizing this relationship to predict at least one component of ground motions. Measured peak overpressure (noise) in the air correlated less directly to the quantities measured on the pile, but a conservative and simple mathematical model can still be proposed based on the dynamic testing-measured velocity near the pile top and idealized sound generation and attenuation theories.
U.S. Army Corps of Engineers Miscellaneous Paper 4-577
Federal agencies engaged in planning facilities for launching or operating spacecraft, heavy weapons, or delicate electronic equipment require accurate and quick information on a soil’s ability to resist deformation over a considerable area for use in site selection and foundation design. Field and laboratory tests and analytical studies have been conducted to develop equipment and procedures for determining the elastic
moduli (and thus the resistance to deformation) of foundation soils by vibratory techniques. This report describes the equipment, measuring techniques, and method of computing the elastic moduli, as developed to date. Since these techniques are relatively new, and the method of computation is still in the development stage, studies to refine them are continuing and results will be published as they become available.
The method and procedure described herein were developed through the work of many consultants and specialists. Much of the basic theory and analytical work was performed by the Royal Dutch/Shell Laboratorium, Amsterdam, Holland. The equipment constructed in the early stages of development of the method has been improved through field usage and experience.
The method employs the measurement of the velocity of waves propagated at known frequencies along the exposed surface of the soil. Determining the velocity of wave propagation over a range of frequencies provides a reliable means of deriving the elastic constants of a soil, and ultimately provides an estimate of its ability to resist deformation. The method has an advantage over conventional soil tests in that it is
applied to soil in situ and enables a considerable area to be tested rapidly. The principle employed has shown great promise, primarily due to the excellent correlation and validation obtained by means of independent laboratory dynamic tests. In the determination of the elastic moduli of a soil by use of vibratory techniques, a basic understanding of dynamics is helpful but not essential.
Michael R. Lewis, Ignacio Arango, PhD and Michael D. McHood
This paper describes site characterization using the cone penetration test (CPT) and recognition of ageing as a factor affecting soil properties. Pioneered by Dr. John H. Schmertmann, P.E. (Professor Emeritus, Department of Civil and Coastal Engineering, University of Florida), these geotechnical engineering methods are practised by Bechtel in general and at the Savannah River Site (SRS) in South Carolina in particular. The paper introduces a general subsurface exploration approach developed by the authors. This approach consists of “phasing” the investigation, employing the observational method principles suggested by R.B. Peck and others.
The authors found that borehole spacing and exploration cost recommendations proposed by G.F. Sowers are reasonable for developing an investigation program, recognizing that the final program will evolve through continuous review. The subsurface soils at the SRS are of Eocene and Miocene age. Because the age of these deposits has a marked effect on their cyclic resistance, a field investigation and laboratory testing program was devised to measure and account for this effect. This paper addresses recommendations regarding the liquefaction assessment of soils in the context of reassessing the SRS soils. The paper shows that not only does aging play a major role in cyclic resistance, but it should also be accounted for in liquefaction potential assessments for soils older than Holocene age.
This dissertation was co-directed by Spencer J. Buchanan, Distinguished Professor of Soil Mechanics and Foundation Engineering at Texas A&M and before that founder and Chief of the Soil Mechanics Division of the U.S. Army Waterways Experiment Station. The Spencer Buchanan Lecture at Texas A&M, an important lecture in geotechnical engineering, is named in his honour.John V. Perry (1924-2009) taught Mechanical Engineering at Texas A&M (with some breaks) from 1948 until 1995.
On a lighter note, his department head, C.M. Simmang (who signed off on the dissertation,) was commenting to his class on a visit by the late President Gerald Ford to San Antonio in 1976. Shaking his head in disbelief, he said, “At least I had enough sense to shuck the tamale before I ate it.”
John Vivian Perry, Jr.
Texas A&M University
This research was undertaken to determine the amount and extent of soil motions under vibrating foundations. The test soil was standard 20-30 Ottawa sand, ASTM C-190, that was contained in a one-meter cubical box. A force generator was mounted above the soil and applied dynamic loads to a circular footing. These were harmonic forces and were applied at frequencies between five and fifty cycles per second.
Three hundred and sixty-seven test runs were recorded on an electromagnetic oscillograph from signals generated by an accelerometer buried in the soil. This accelerometer was located at various depths beneath the centre of a footing and, at other times, it was located beneath and off centre. Other variables were the footings which had different diameters and masses.
Three empirical equations were developed from the test results using dimensional analysis. These equations were for maximum values of acceleration, velocity and displacement, respectively.
a vulcanhammer.net special
Controlling environmental effects of civil engineering operations has always been of concern to all parties involved in the construction process. Since control is exercised through the responsibilities outlined in contract specifications, these details are important. This work specifically addresses specifications that incorporate recent developments in the control of external construction vibration effects. These technical vibration specifications are intended to establish controls for the protection of nearby structures from ground vibrations, permanent ground deformation, emission of projectiles, and low frequency air over pressures. Annoyance of neighbours from noise and vibration intrusion also must be taken into account.
An attempt is made in this thesis to present suitable specifications for all types of blasting encountered today in civil engineering projects: production rounds, controlled, close-in and demolition blasting, as well as blast densification of sands. Special chapters deal with vibrations and soil displacement caused by pile driving, and with air overpressure’s created by both blasting and piling engineering.
The following conclusions are advanced, among others, concerning the geotechnical, the procedural, and the management aspects of vibration control specifications. It is necessary to take vibration considerations into account in the design of the project. This can be accomplished by making preconstruction surveys, by incorporating frequency considerations, and by setting realistic particle velocity limits. The specification should ask the contractor to meet given requirements, but should leave the choice of the method to his ingenuity. Specialists of the operations carried out on the site should be hired by the contractor, and test programs should always be performed before the start of full scale activities. Monitoring of vibration effects, such as peak particle velocity and air overpressure’s, requires special schemes, especially for pile driving, where two threshold values of particle velocity should be introduced. The engineer should not be considered only as the control authority, but also as a skilled person whose advise on specific problems can be valuable.
Technical Review and Comments: 2008 EERI Monograph “Soil Liquefaction During Earthquakes” (by I.M. Idriss and R.W. Boulanger)
Webmaster’s note: my own decidedly “non-technical” take on this subject is here.
Raymond B. Seed
University of California at Berkeley
Geotechnical Report No. UCB/GT–2010/01
From Dr. Seed’s Introduction:
“The recently published monograph by Idriss and Boulanger (2008), issued by the Earthquake Engineering Research Institute as part of their ongoing monograph series, presents a number of potentially important correlations and recommendations for assessment of potential hazard associated with seismically induced soil liquefaction. It is important that these recommendations be reviewed, and I have been asked to undertake such a review by a number of individual engineers as well as by a number of agencies and engineering firms.
“The views presented herein are my own, and do not represent the institutional views of any particular agency or other organization(s).
“The materials and recommendations presented in the monograph proceed in several distinct sections, and this review will not address all of these in detail. Chapters 1 and 2 of the monograph present an introduction to the general principles and phenomena associated with soil liquefaction, based largely on a good sampling of the works of others, and I will not address these chapters except to note that they are well written and provide a very useful introduction to the subject. Sections 4.3 through 4.6 similarly introduce a number of topics and issues associated with beginning to predict the consequences of soil liquefaction, but without attempting to resolve these into firm, quantitative recommendations for application to practice. This, too, is a generally useful discussion and it will not be reviewed in detail.
“Finally, Chapter 5 presents a few thoughts regarding mitigation of soil liquefaction hazard. This is a short treatment, and I will not provide a review of that chapter either. The remaining sections of the monograph present five potentially important sets of recommendations, and these will be reviewed in detail herein…”
This work is a classic for soil dynamics in general and the response of soil to the vibration of foundations in particular. Lysmer’s simplification of the response equation was a major step forward in the rational analysis of this phenomenon.
Lysmer’s Analogue–which reduced the soil response of a rigid circular foundation to a single degree of freedom spring-dashpot system–also has found application in pile toe response to pile driving, as was discussed in thesis Closed Form Solution of the Wave Equation for Piles.
John Lysmer was for many years a Professor of Civil Engineering at the University of California at Berkeley. He passed away in 1999.
U.S. Army Corps of Engineers Contract Report 3-115
University of Michigan
This investigation includes a theoretical solution for a rigid footing, resting on an elastic half-space, which is subjected to steady-state vertical oscillation. It is shown how this steady-state solution can be used to describe the response of the footing to a transient pulse-type vertical loading.
After establishing the theoretical solution, and evaluating the approximations required for its development, it is further demonstrated that the theory permits evaluation of quantities which may represent spring constants and damping factors for use in the usual theory for vertical motion of a damped-one-degree-of freedom system. The agreement between the simple theory and elastic half-space theory is well within the limit required for engineering solutions.
The results of the study provide information from which the elastic dynamic response of rigid footings subjected to transient vertical loads may be evaluated. By taking advantage of such standard procedures as the phase-plane method, the dynamic response of footings may still be estimated even if the stresses in the soil extend into the inelastic range. A detailed discussion of the application of this method to inelastic settlements of vertically loaded footings will be presented in a subsequent report.
Finally, the theoretical developments included in this report for vertical oscillations may serve as a guide to develop similar theoretical evaluations of the dynamic response of rigid footings in other uncoupled modes of oscillation.