Dynamic replacement

Dynamic replacement can be used to increase the strength of (saturated) soft cohesive and organic soils and to reduce the settlements during future loading conditions. 

Depending on the consistency of the subsoil replacement ratios of 20-25% can be achieved, increasing both the strength and stiffness of the treated strata considerably. As a result of the large diameter, significant loads can be supported by individual columns. 

The method is considered to be cost effective and fast, but can only be undertaken in soft soils and to limited depths. 

Should long columns be required, then the location of a column can be preexcavated and (partly) fiUed with aggregate before tamping starts. This will also reduce the heave of the surrounding soil. 

Although generally used on land, underwater applications have been reported by Hamidi et al. (2010) installing dynamic replacement columns at water depths of up to 30 m. 

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Zhang H, Pan J, Chimire S, Bork MA, Riccitelli MM, McMillin DR, Hyun Choi J. Regeneration of light-harvesting complexes via dynamic replacement of photodegraded chromophores. ACS Appl Mater Interf 2015 7 7833-7. 

Sand compaction piles (closed end casing) 7.6.5 Geotextile encased columns 7.6.6 Dynamic replacement ... 

During compaction, heave of the surface in the immediate vicinity of the columns can occur and may have to be cut down. Figure 7.24 shows the exposed top of a number of dynamic replacement columns after installation and subsequent excavation. 

Figure 7.24 Top of dynamic replacement columns after installation and excavation (info Menard).

Hamidi, B., Nikraz, H., Yee, K., Varaksin, S. and Wong, L.T. Ground improvement in deep waters using dynamic replacement. Proc. 20th Int. OfMiore and Polar Engineering Conf, Beijing, China, 2010. 

As with most methods for studying ion-molecule kinetics and dynamics, numerous variations exist. For low-energy processes, the collision cell can be replaced with a molecular beam perpendicular to the ion beam [106]. This greatly reduces the thennal energy spread of the reactant neutral. Another approach for low energies is to use a merged beam [103]. In this system the supersonic expansion is aimed at the tluoat of the octopole, and the ions are passed tluough... 

The calculation of the time evolution operator in multidimensional systems is a fomiidable task and some results will be discussed in this section. An alternative approach is the calculation of semi-classical dynamics as demonstrated, among others, by Heller [86, 87 and 88], Marcus [89, 90], Taylor [91, 92], Metiu [93, 94] and coworkers (see also [83] as well as the review by Miller [95] for more general aspects of semiclassical dynamics). This method basically consists of replacing the 5-fimction distribution in the true classical calculation by a Gaussian distribution in coordinate space. It allows for a simulation of the vibrational... 

The standard discretization for the equations (9) in molecular dynamics is the (explicit) Verlet method. Stability considerations imply that the Verlet method must be applied with a step-size restriction k < e = j2jK,. Various methods have been suggested to avoid this step-size barrier. The most popular is to replace the stiff spring by a holonomic constraint, as in (4). For our first model problem, this leads to the equations d... 

Finally, it should be pointed out that all the results on dynamical testing presented here are correct only if the tracer gas is not significantly adsorbed at the solid surface. If it is adsorbed weakly, so that a linear isotherm is appropriate, the equations should be modified by the following replacements ... 

Rather than solve a Schrodinger equation with the Nuclear Hamiltonian (above), a common approximation is to assume that atoms are heavy enough so that classical mechanics is a good enough approximation. Motion of the particles on the potential surface, according to the laws of classical mechanics, is then the subject of classical trajectory analysis or molecular dynamics. These come about by replacing Equation (7) on page 164 with its classical equivalent ... 

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