Impact of Weight Falling onto the Ground

Dynamic compaction (DC) is a common soil improvement technique, used extensively worldwide. DC treatment design is usually based upon empirical relations and past experience. The common problem with all empirical relations is oversimplification of the mechanisms, and the use of parameters that are highly dependent on engineering judgement. In this paper, a developed finite-element code is used for modelling the impact behaviour of dry and moist sandy soil. The code is verified against the results of centrifuge tests. Then the validity of the popular Menard empirical relation for determination of improvement depth in DC design is investigated. The effect of initial relative density, tamper radius, number of drops, and the impact energy are studied using the developed numerical model. It was found that Menard's empirical relation yields suitable results when tamper weight and falling height are both in the ordinary ranges. However, for higher impact energies, Menard's relation overestimates the depth of improvement. The obtained results also indicate that the value of the empirical coefficient in Menard formula depends strongly on the applied energy and tamper radius. Based on this finding, a new relation for predicting the improvement depth is proposed and applied to a number of DC projects. The results show that the new relation provides better results than the old formula.

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“…[11][12][13][14] The main limitation of one-dimensional models is that no information can be obtained about the lateral extent of improvement.…”

Section: Numerical and Experimental Modelsmentioning

confidence: 99%

Validity of Menard relation in dynamic compaction operations

Ghassemi

Pak

Shahir

2009

Proceedings of the Institution of Civil Engineers - Ground Impr

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“…The KV representation has traditionally been used to mathematically describe the dynamics of soils in engineering practice. Examples include consolidation (ASTM-D2435, 1996) and resonant column (ASTM- D4015, 1996) tests, as well as the response of soils under impact (Roesset et al, 1994). A significant limitation is the single mass element in the model.…”

Section: Beyond the Kelvin-voigt (Kv) Representation For Shear Wavesmentioning

confidence: 99%

Comparison of Viscous Damping in Unsaturated Soils, Compression and Shear

Michaels

2006

Unsaturated Soils 2006

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Geophysical down-hole surveys can be used to measure the small strain dynamic properties of soils by the effects these properties have on wave propagation. The relevant effects include amplitude decay (corrected for beam divergence) and velocity dispersion. In this paper, down-hole data collected during the GeoInstitute's Denver 2000 field day are presented and analyzed as a Kelvin-Voigt solid. Findings for these unsaturated soils include viscous damping and stiffness which differ significantly for shear and compressional waves. A strong viscous damping is observed in compression, but weak damping is presented in shear. Lumped parameter constitutive models are discussed which mathematically represent the soil dynamics.It appears that, in the case of unsaturated soils, the relatively low level of viscous damping in shear may be explained by the low mass of the air in the pores. That is, it is difficult for inertial decoupling to occur between the soil frame and the pore fluid when the pore fluid (air) is of such low density. Thus, a pore fluid in coupled motion with the frame can not produce significant viscous drag. On the other hand, large viscous damping is observed for compressional waves. This larger damping may be due to the larger relative motions between air and frame which can be forced by compression of the frame matrix. These observations may be relevant in areas such as the design of driven piles and the estimation of potential for damages from vibrations due to construction.

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“…A popular approach for studying the dynamic site response of a 1D soil column is the approximation through a single-degree-of-freedom (SDOF) system (Roesset et al, 1994). In general, methods for analyzing the dynamic response of SDOF systems can be based in both the time and frequency domains.…”

Section: Introductionmentioning

confidence: 99%

Ground‐Motion Forecasting Using a Reference Station and Complex Site‐Response Functions Accounting for the Shallow Geology

Pilz¹,

Parolai²

2016

Bulletin of the Seismological Society of America

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The distribution of damage due to recent earthquakes has shown that the effects of shallow geological structures on the level of ground shaking represent an important factor in engineering seismology. Whereas many previous studies have estimated site amplification factors in the frequency domain, their application to the realtime modeling of ground motion is not yet fully established. In this article, a method for the real-time correction of frequency-dependent site-response factors is proposed, which accounts not only for the modulus, but also for the changes in the signal phase related to local site conditions. The transformation of the complex standard spectral ratios to a causal recursive filter in the time domain allows for the forecasting of the waveforms for soft-soil sites almost in real time when the signal is recorded earlier at a reference site. When considering travel-time differences of the various seismic phases between the hypocenter and the studied sites, the level of ground motion at soft-soil sites with respect to arrival time, energy, duration, and frequency content can be well constrained, even in cases of a high spatial variability of the amplification patterns.

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Impact of Weight Falling onto the Ground

Cited by 46 publications

References 0 publications

Validity of Menard relation in dynamic compaction operations

Validity of Menard relation in dynamic compaction operations

Comparison of Viscous Damping in Unsaturated Soils, Compression and Shear

Ground‐Motion Forecasting Using a Reference Station and Complex Site‐Response Functions Accounting for the Shallow Geology

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