ICE - Institution of Civil Engineers - Virtual Library

This case study presents the design, operation and evaluation of a soil improvement project using vertical drains in conjunction with a surcharge fill for preloading the soil for the construction of a 370 m long quay wall. Although the technique was assumed feasible for the soil material, no significant effects of soil improvement were measured. Settlement, pore water pressure and spectral analysis of surface waves (SASW) measurements before, during and after the loading showed no extreme increase in density or stiffness parameters. An explanation for this behaviour is thought to be the underestimation of the stiffness and preloading stress of the softer layers.

L'étude de cas présente la conception, la réalisation et l'évaluation d'un projet d'amélioration des sols au moyen de la méthode de préchargement avec drains verticaux pour la construction d'un quai de 370 m de longueur. Quoique la technique soit supposée applicable, aucuns effets significatifs d'amélioration n'étaient mesurés. Mesures de tassements de consolidation, des pressions interstitielles et des vitesses d'onde par la technique SASW pendant, durant et après le chargement n'indiquent d'augmentation importante de densité. L'explication de ce comportement peut ê tre la sous-estimation de la rigidité et de la contrainte de préconsolidation des couches les plus molles.

This article presents the spectral analysis of surface waves (SASW) technique and describes an experimental investigation concerning its ability to non-destructively assess the variation of elastic properties within Portland cement concrete structures. SASW tests were conducted on three concrete slabs, 1·4 m × 1 m × 0·5 m in size, and having different compressive strength (f′_c: 17·5, 27 and 53 MPa). Tests were also conducted on a layered concrete slab, 2 m × 2 m × 0·7 m in size, and made up of a base layer, an intermediate layer and a top layer having compressive strength of 53, 27 and 17.5 MPa, respectively. The results show that the propagation velocity of Rayleigh waves is very sensitive to variations in concrete quality and that the SASW technique offers a practical tool to determine the extent of near-surface damage observed in in-service concrete structures.

Dynamic compaction technique has been employed to improve the mechanics properties of soils since 70's (Menard & Broise, 1975). This work presents the results of two dynamic compaction tests, which where done over municipal solid waste and inert waste materials. Application of this technique seeks a way of achieving a strengthening materials and increasing the capacity of the landfills due to an increase in density of these materials.

This paper includes results from two tests that were carried out in the MSW landfill “Las Dehesas” and in the inert waste landfill “Las Cumbres”, both belonging to the “Complejo Medioambiental de Valdemingómez” (Madrid, Spain). Before the development of the test a geotechnical research campaign was done. Mechanical borehole and in situ test were carried out. Then the dynamic compaction tests were carried out and the quality of the work was controlled by dynamic penetration test and by Spectral Analylis of Surface Waves (SASW) tests.

• Introduction

• Inert waste landfill

• Municipal Solid Waste (MSW) Landfill

• Conclusions

• Acknowledgments

• References

A collapse developed at Calvert Cliffs Nuclear Power Plant, Maryland, in early 2001. The location of the collapse was over a groundwater drainage system pipe buried at an elevation of +0·9 m (reference is to Chesapeake Bay level). The cause of the collapse was a subsurface drain pipe that collapsed because of saltwater corrosion of the corrugated metal pipe. The inflow/outflow of sea water and groundwater flow caused soil to be removed from the area where the pipe collapsed. To prevent damage to nearby structures, the collapse was quickly filled with uncompacted sand and gravel (∼36 000 kg). However, the plant had an immediate need to determine whether more underground voids existed. A high-frequency multichannel surface-wave survey technique was conducted to define the zone affected by the collapse. Although the surface-wave survey at Calvert Cliffs Nuclear Power Plant was conducted at a noise level 50–100 times higher than the normal environment for a shallow seismic survey, the shear (S)-wave velocity field calculated from surface-wave data delineated a possible zone affected by the collapse. The S-wave velocity field showed chimney-shaped low-velocity anomalies that were directly related to the collapse. Based on S-wave velocity field maps, a potential zone affected by the collapse was tentatively defined.

• 11.1. Introduction

• 11.2. Case study

• 11.3. Measurements

• 11.4. Dynamic properties of soil and embankment materials

• 11.5. Numerical simulation

• 11.6. Countermeasures

• 11.7. Physical model

• 11.8. Environmental vibration

• 11.9. Conclusions

• 11.10. Acknowledgements

• 11.11. References

Transient stress waves offer a powerful approach for non-destructive condition evaluation of concrete structures. However, currently used stress-wave-generating techniques are limited by poor controllability and/or penetrating ability. Stress wave generation must therefore be improved so that the application of existing and new ultrasonic and sonic non-destructive testing techniques to concrete structures will be more effective. This paper first summarizes the existing, traditional stress-wave-generating techniques for testing concrete structures. A method by which electromagnetic and piezoelectric-based sources are driven by AM burst signals is then introduced, fully detailed and shown to be appropriate for concrete tests in place of traditional sources. The performance of these sources is demonstrated through the results of impact-echo tests and spectral analysis of surface waves performed on a Portland cement concrete structure.

• 10.1. Introduction

• 10.2. The in situ measurements

• 10.3. Experimental results

• 10.4. Krylov's analytical prediction model

• 10.5. Analytical predictions

• 10.6. Conclusion

• 10.7. Acknowledgements

• 10.8. References