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Ground reinforcement anchorages are a means of ensuring the stability of a wide range of structures and retaining walls. The performance of an individual anchorage depends on the tensile load that the anchorage is carrying but this will change over the anchorage's life span, so it is therefore necessary to have some way of measuring this load. A nondestructive technique, ground anchorage integrity testing (GRANIT), in which impulse responses of anchorages are determined to evaluate whether load transfer is maintained, has previously been developed for anchorages in rock. This research examines the possibility of extending this to soil anchorage systems. In this work, implementation of a model nondestructive testing system is tested using a geotechnical centrifuge. Load distributions along centrifuge model anchorages are measured and found to reduce gradually within the fixed length, as is the case with rock. Anchorage frequency responses to impulse loads are then evaluated to validate the consistency of the results obtained. Various anchorage inclinations and fixed lengths are also investigated, showing that inclined anchorages contain a greater range of frequencies in their signature response. The practical importance of these results is that nondestructive testing may be usable for anchorages in soil as well as anchorages in rock. Further investigation is necessary to refine the relationship between anchorage load and response frequencies. This may be accomplished using centrifuge modeling. [ABSTRACT FROM AUTHOR]

High spatial resolution () neutron tomography was performed on partially water-saturated compacted silica sand specimens with two different grain morphologies (round and angular) at Helmholtz Zentrum Berlin using cold neutrons at the cold neutron radiography and tomography beam line. A specimen mixed with heavy water was imaged for contrast comparison purposes. Microfocus X-ray imaging was also performed on these specimens with slightly higher resolution () using geometric magnification to locate the solid phase (silica particle boundaries) more precisely. Image processing was performed to remove unwanted gammas detected because of the gadox scintillator used for the high-resolution neutron imaging system. The visualization of solid, gas, and liquid phases for different grain morphologies is presented at the grain level. Using dual-modal contrast possible from simultaneous use of neutrons and X-rays, the authors introduce, for the first time, an improved ability to distinguish solid silica, liquid water, and gas phases. Quantitative analysis using three-dimensional tomography data is demonstrated for obtaining void ratio, void percentage variation over the height, and particle size distribution. [ABSTRACT FROM AUTHOR]

Material damping is a fundamental parameter required for dynamic analysis of geotechnical and civil infrastructure. The material damping ratio is very difficult to measure in situ. A new methodology for in situ measuring of material damping using surface waves is presented in this work. This methodology is successfully evaluated on laboratory scale models and numerical simulations. Ultrasonic waves are used in this work because of the size of the laboratory models. The output force of an ultrasonic piezoelectric transmitter is modeled by using a Morlet function. The wave attenuation and phase variation of propagating surface waves with distance are analyzed using the wavelet transform. Numerical results show that the material damping ratio calculated using the wavelet transform gives a global value that represents an average damping ratio for the frequency bandwidth imposed by the seismic or ultrasonic source. Experimental results, from tests on a cemented sand and a concrete plate, show good agreement with published damping values. [ABSTRACT FROM AUTHOR]

This paper presents the process and results of a quality management program performed during and immediately after the construction of two deep soil mixing (DSM) test sections. The quality management program consisted of laboratory, in situ, and mineralogical tests to address the effectiveness of the treatment during and after construction. In situ investigations including the down-hole seismic and spectral analysis of surface waves (SASW) test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the columns and surrounding soils. Scanning electron microscopy and electron dispersive x-ray analysis were performed on raw, laboratory treated and field-treated specimens for qualitative understanding of the degree of mixing achieved in the field and the compounds formed at particle level during stabilization, respectively. Laboratory tests results on field cores indicated that both field stiffness and strength are about 20 to 40% less than the corresponding laboratory prepared soil samples. The down-hole seismic and SASW tests showed considerable improvement in stiffness in and around the DSM columns. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of lime-cement treated clay particles in both laboratory and field specimens, suggesting adequate mixing of the soil and binder in both environments. [ABSTRACT FROM AUTHOR]

Soil compaction quality control plays an important role in earthwork construction. Compacted dry density is only loosely related to the actual deformation of the compacted soil. Rather than using dry density as the controlling factor for compacted fills, it would be better to measure properties more closely related to soil compressibility. The Briaud compaction device (BCD) is a simple, small-strain, nondestructive testing apparatus that can be used to evaluate the modulus of compacted soils. The use of the BCD as a field testing device for compacted soil quality control may be more beneficial than the current practice of measuring in situ dry density. In this study, the laboratory procedures of the BCD were evaluated for compacted silt. The modulus determined by the BCD was compared to the dynamic elastic moduli (Young’s and shear moduli) determined from ultrasonic pulse velocity testing on the same compacted silt samples. The BCD modulus correlated well with the ultrasonic pulse velocity results with R2 value of 0.8 or better. Finally, a repeatability and reproducibility study conducted on the BCD showed a variation of 4% from the mean when only the soil properties were altered. [ABSTRACT FROM AUTHOR]

While improvements in equipment and sampling methods have enabled collection of better quality samples of soft clays for more reliable engineering design and performance prediction, current sample quality assessment methods typically require destructive laboratory testing performed long after samples are taken. This paper describes a nondestructive technique for sample quality assessment of soft clays using shear wave velocity. A portable bender element device was used to measure shear wave velocity (Vvh) in the field immediately following collection of Sherbrooke block, tube, and split spoon samples of Boston blue clay. Vvh values were compared to in situ values from seismic piezocone (VSCPTU) tests. The ratio Vvh/VSCPTU was compared with results from a conventional, laboratory-based assessment method. Results indicate a consistent correlation between laboratory-based methods and the Vvh/VSCPTU ratio, which ranges from Vvh/VSCPTU=0.77 for the block samples to 0.28 for split spoon samples. The portable bender element device and nondestructive assessment technique offer the potential for field quality assessment and allow for real time adjustments to sampling techniques and/or more effective selection of samples for laboratory testing. [ABSTRACT FROM AUTHOR]

The case history of a sudden and unexpected failure in a pavement designed for 82 Mg axle loads at Port Botany in Sydney, Australia has been prepared using data derived from investigation of the failure. Failure of the pavement, comprised of an asphaltic concrete surface, unbound granular fine crushed rock base, crushed sandstone subbase, and sandy subgrade, and designed using the rational method—CIRCLY, occurred within days of being put into service. The failure resulted from a 20–30% increase in base course saturation levels following compaction that led to partial liquefaction under repeated heavy loading. There was a general failure throughout the storage area where trafficking was most intense and the pavement remained intact in lightly trafficked areas. The intact areas recovered over time without intervention through a moisture equilibration process as evidenced by an increase in measured pavement stiffness and loss of moisture within the pavement profile. [ABSTRACT FROM AUTHOR]

Defects present in a pile may not be encountered during a cross-hole sonic logging (CSL) test. Even when defects are indeed encountered, they may not always be detected. This paper proposes a probabilistic analysis procedure for evaluating the reliability of CSL, thereby providing a theoretical supplement to existing experimental evaluations of CSL. The reliability of this integrity testing method is represented by the inspection probability, which is expressed as the product of the encountered probability and the detection probability. Mathematical models to calculate the encountered probability are formulated and a detection probability model is suggested based on existing CSL test data. Several examples are presented to illustrate the proposed procedure. The results indicate that there exists a minimum detectable defect size below which the defect cannot be inspected. For a given number of access tubes, the minimum detectable defect size, as a percentage of the pile cross-sectional area, decreases with the pile diameter. The encountered probability can be taken as an index to determine the required number of access tubes. When the target encountered probability is specified as 0.95, three and four access tubes will be sufficient to encounter defects larger than 15 and 5% of the pile cross-sectional area, respectively. [ABSTRACT FROM AUTHOR]

Analysis of seismic surface waves offers a noninvasive method to estimate the dynamic engineering properties of the near-surface earth. Traditional two-sensor spectral analysis of surface waves (SASW) techniques suffer from several limitations that impede their use in practice, including poor resolution, inability to properly account for multiple modes, and an imprecise understanding of near-field effects. Current multichannel and array analysis of surface waves resolve several of these limitations, but still suffer from a near-field model incompatibility, i.e., estimating plane wave parameters in a cylindrically spreading wave field. This paper introduces cylindrical beamforming, an array processing method to overcome the limitations of plane wave processing methods. To aide in motivating the cylindrical beamformer, the paper discusses the near-field effects and explains some of the underlying physical reasons for previous observations regarding the near-field. The cylindrical beamformer is then introduced to more accurately model the wave field, allowing better estimates of phase velocity from point sources. The results from measured data taken with a linear array on a site in Atlanta are used to compare the methods. [ABSTRACT FROM AUTHOR]

This paper presents the results of nondestructive integrity tests (NDTs) and axial static load tests on drilled shafts constructed in varved clay at the National Geotechnical Experimentation Site in Amherst, Mass. The shafts were constructed with built-in defects to study: (1) the effectiveness of conventional NDT methods in detecting construction defects and (2) the effect of defects on the capacity of drilled shafts. Defects included voids and soil inclusions occupying 5–45% of the cross section as well as a soft bottom. Nine organizations participated in a blind defect prediction symposium, using a variety of NDT techniques. Most participants located defects that were larger than 10% of the cross sectional area. However, false positives and inability to locate smaller defects and multiple defects in the same shaft were encountered. Static load tests indicated that (1) minor defects had little or no effect on skin friction; (2) a soft bottom resulted in a 33% reduction in end bearing relative to a sound bottom; and (3) reloading resulted in a 20–30% reduction in the geotechnical capacity. [ABSTRACT FROM AUTHOR]

Results of low strain integrity testing of piles are normally interpreted using one-dimensional (1D) stress wave theory. While 1D stress wave theory is acceptable for pile-driving analysis, it may not adequately simulate the response of piles in sonic integrity tests where the hammer is small in relation to the size of the pile. Extensive parametric studies were performed using 1D and 3D (axisymmetric) wave equation models to study this problem. The main 3D effect in intact piles lies in the initial velocity response that becomes negative after the first positive peak. This response resembles that of a pile with an anomaly near the pile head. If this is not recognized, it will lead to a wrong assessment of the pile condition with attendant cost implications. This potential source of error can be removed by maintaining a distance between hammer and receiver that is greater than 50% of the pile radius. [ABSTRACT FROM AUTHOR]