Richard D. Woods

Numerical simulation of the SASW test

The paper describes numerical simulation of the SASW test. Influences of the test setup and applied filtering criteria on the accuracy of the obtained field dispersion curve for various soil stratification conditions have been examined. The results presented indicate significant variations in the evaluated dispersion in cases of irregular soil profiles if the existing criteria are applied. A new filtering criteria has been proposed.

Resonant Column Tests on Partially Saturated Sands

This paper describes the measurement of the influence of capillary effects on the dynamic shear modulus of partially saturated sands. A Hall-type resonant column apparatus was used to perform the experiments. The materials tested included natural angular and subrounded sands, angular and subrounded sands with specified artificial gradations, and uniform angular and subrounded sands with various minus No. 400 sieve size fractions. Capillary stresses can significantly increase the shear modulus of unsaturated sands. Void ratio, confining pressure, degree of saturation, grain shape, and grain-size distribution are the primary factors affecting the shear modulus of partially saturated sands.

Development of Model for Shear-Wave Velocity of Municipal Solid Waste

AbstractThe shear-wave velocity and associated small-strain shear modulus of municipal solid waste (MSW) are important engineering parameters in evaluating the seismic response of MSW landfills as well as in characterizing the waste material and its response to static loads. Semiempirical and empirical models for the shear-wave velocity are presented. The semiempirical model is a more comprehensive model that aims to separately capture the effect of waste density and confining stress on the shear-wave velocity of MSW. It is based on similar models for soils, and its mathematical expression is formulated using data generated from large-scale laboratory studies on reconstituted MSW. The empirical model has a simpler mathematical expression that is a function of depth only. The parameters of both models are derived by calibrating them against a total of 49 in situ shear-wave velocity profiles at 19 MSW landfills, i.e., 13 profiles from four landfills in Michigan generated as part of this study and 36 additio...

A Device for Evaluating One-Dimensional Compressive Loading Rate Effects

It has long been suggested that the one-dimensional or uniaxial strain response of most soils subjected to high-intensity transient loads differs from the response measured under static conditions. As the time to peak pressure decreases, most soils exhibit a stiffening of the loading stress-strain response. That stiffening is usually referred to as a time or loading rate effect. Some researchers have suggested that, as the time to peak pressure approaches the submillisecond range, a drastic increase (up to tenfold) in the loading constrained modulus occurs for partially saturated granular soils under unconsolidated-undrained conditions. The existence of this effect has been the subject of debate. A test device was developed at the U.S. Army Engineer Waterways Experiment Station using explosives to obtain submillisecond loading times to peak pressures of approximately 138 MPa (20 000 psi). By using state-of-the-art measurement and acquisition systems, an accurate measurement of the uniaxial stress-strain response to submillisecond loadings was obtained. This paper presents the details of that device and the associated electronic measurement and acquisition systems, testing techniques, data interpretation, and typical test results used in assessing loading rate effects of a partially saturated carbonate sand. Results showed that a drastic stiffening did not occur for this material as the time to peak pressure approached the submillisecond range. Instead, a gradual stiffening occurred and the basic shape of the stress-strain curve was maintained.

Influence of Source and Receiver Geometry on the Testing of Pavements by the Surface Waves Method

The spectral analysis of surface waves (SASW) method is a nondestructive testing procedure under development for determining the elastic modulus profile of pavement systems in situ. The ultimate goal in the development of the SASW method is a totally automated, moveable test rig for conducting the investigation. An important step toward this objective is the development of a multiple transducer testing procedure. A significant variable with respect to a multiple transducer testing procedure is the choice of source and receiver geometry. A series of tests were conducted on an asphaltic concrete pavement to study the influence of source and receiver geometry. It was found that the results obtained from two different geometries, the common receivers midpoint (CRMP) geometry and the common source (CS) geometry, were nearly identical. The common source (CS) geometry was concluded to be preferable because of its practical advantage of a fixed source location.

Field Testing Method for Evaluating the Small-Strain Shear Modulus and Shear Modulus Nonlinearity of Solid Waste

Dynamic properties of solid waste are needed to reliably evaluate the seismic response of landfills. A testing method for investigating the dynamic properties of solid waste in situ has been implemented at various landfills. The field method is primarily aimed at evaluating shear wave and compression wave velocities at small strains as well as the shear modulus reduction versus shearing strain relationship of solid waste. In this study, shear modulus nonlinearity was successfully evaluated for shearing strains ranging from 10–4 to 0.2 %. The relationship between shear modulus and shearing strain was investigated by applying dynamic horizontal loads applied by a mobile field shaker at the waste surface in a staged-loading sequence. The solid waste response was measured with a buried array of three-component geophones. The testing method also permitted in situ assessment of the effect of confining stress and waste variability on the dynamic properties of solid waste. Load-settlement measurements and in situ unit weight measurements were also made. Testing equipment, field setup, testing procedure, data analysis, and examples of test results are presented.

Ground Vibration Measurements near Impact Pile Driving

Pile driving is a complex dynamic process where little insight has been garnered in terms of the energy transfer from the driver to the soil and surrounding structures. Ground motion measurements during driving of full scale steel H-piles with diesel hammers are presented. The key feature of this work is the in-depth sensor installation starting very close to the pile (0.2 m), at other radial distances from the pile, and at various depths in the ground. Differences in wave sources from the tip and the shaft of the pile as well as wave attenuation coefficients are revealed from the sensor measurements. Attenuation relationships fitted through the data could be used to predict ground motion that could cause shakedown settlement. A conventional line array of surface mounted geophones was also used and results are presented.

Measurement of Ground Motion near Piles during Driving

Two types of vibration damage caused by driving piles have been reported in the literature: direct structural damage and damage due to settlement. Direct damage results from vibratory excitation of structures at amplitude exceeding the structural tolerance. Damage from settlement is a consequence from vibratory densification of loose soils resulting in total or differential settlement of structures. Problems of settlement due to pile driving have been experienced recently by the Michigan Department of Transportation (MDOT) during operations associated with replacement of deteriorating bridges. The work described here represents an attempt to understand the mechanisms of energy transfer from steel H-piles driven with diesel hammers to the surrounding soil and the energy attenuation through the soil by measuring ground motion in the near vicinity of the pile. The main feature of this study consisted of installing motion transducers very close, within 0.5 foot, to piles and measuring the resulting ground motion during pile driving. Selection, fabrication, and installation of the transducers and preliminary measured pile driving vibrations are presented.

Applications of Shear Wave Velocity In Static Problems

There are many applications where shear wave velocities can be used in static geotechnical engineering problems. Moduli obtained by elastic wave propagation techniques are valuable in many design applications including two which are described involving wind induced, building rocking and bridge abutment settlement. Other applications involve the use of elastic wave velocities to evaluate the extent and degree of change produced by ground improvement techniques. One example is described in which chemically grouted soil was used in place of underpinning in coarse, saturated soil. In another example compaction grouting in talus deposits was checked with crosshole tests. New crosshole equipment which can be used in boreholes or grout holes as small as 12 inch diameter is described. Laboratory tests performed to confirm assumptions pertaining to the relationship between shear wave velocity and unconfined compression tests are also presented. Two of the applications described are associated with completion of I-70 through Glenwood Canyon of the Colorado River.

Foundations for auto shredders

Abstract Unbalanced forces developed by hammer wear and impact must be resisted by auto shredder foundations. Methods for estimating the impact forces are described. Because of different soil conditions, a concrete mat, a concrete block, and a pile-supported foundation system were adopted at three different construction sites. The design procedures involved in determining the dynamic response for each type of foundation are illustrated by examples. Vibration measurements made on the pile-supported foundation after construction permitted comparisons of prototype motions with design predictions.