the Geotechnical Nest

SeismoSelect is an easy and efficient way to search, select, scale and download ground motion data from different strong motion databases that are available on-line. Different criteria may be employed as the parameters of interest, with which to carry out the searches. These include a target response spectrum, different ground motion parameters (e.g. PGA, PGV, Arias or Housner Intensity), information regarding the event (e.g. magnitude, faulting style location, date) or the recording site (e.g. Vs30, epicentral distance). SeismoSignal constitutes an easy and efficient way for signal processing of strong-motion data, featuring a user-friendly visual interface and being capable of deriving a number of strong-motion parameters often required by engineer seismologists and earthquake engineers.

SeismoMatch is an application capable of adjusting earthquake accelerograms to match a specific target response spectrum, using the wavelets algorithm proposed by Abrahamson and Hancock or the algorithm proposed by Al Atik and Abrahamson. After loading some accelerograms and defining the target response spectrum, users need only to define the spectral matching algorithm, adjust the spectral matching period range, set the required tolerance and the spectral matching is executed. SeismoArtif is an application capable of generating artificial earthquake accelerograms matched to a specific target response spectrum using different calculation methods and varied assumptions. It is noted that the use of real accelerograms and spectrum matching techniques, together with records selection tools, tends to be recommended for the derivation of suites of records for use in nonlinear dynamic analysis of structures. However, in those cases where access to real accelerograms is, for whatever reason, challenging or inappropriate, then a tool such as SeismoArtif will be of pertinence and usefulness.

SeismoSpect constitutes a simple and efficient platform for signal processing that allows to create a personal library of ground motion records and save them all in a single file making it easy to handle and share large numbers of records. FRP Designer provides an efficient solution for designing FRP strengthening of reinforced concrete columns and beams by computing the strength of reinforced concrete members strengthened with FRP laminates.

Ground improvement has been one of the most dynamic and rapidly evolving areas of geotechnical engineering and construction over the past 40 years. The need to develop sites with marginal soils has made ground improvement an increasingly important core component of geotechnical engineering curricula. Fundamentals of Ground Improvement Engineering addresses the most effective and latest cutting-edge techniques for ground improvement.

Key ground improvement methods are introduced that provide readers with a thorough understanding of the theory, design principles, and construction approaches that underpin each method. Major topics are compaction, permeation grouting, vibratory methods, soil mixing, stabilization and solidification, cutoff walls, dewatering, consolidation, geosynthetics, jet grouting, ground freezing, compaction grouting, and earth retention.

The book is ideal for undergraduate and graduate-level university students, as well as practitioners seeking fundamental background in these techniques. The numerous problems, with worked examples, photographs, schematics, charts and graphs make it an excellent reference and teaching tool.

Since unit weight is total weight divided by total volume:

For a given soil (the subject soil) the effective unit weight when submerged (or the submerged effective density) will be the same regardless of depth below the water surface.

For the condition where the soil is 100 percent saturated and the wet unit weight is known, the equations for submerged soil unit weight reflect that the weight (or mass) of both the soil particles and the voids water are for the buoyant condition, to become:

The equation indicates that an accurate determination of the submerged unit weight requires that the specific gravity of the soil solids and the void ratio be known. Unfortunately, in terms of time and expense, some testing or physical analysis is required to determine the specific gravity, which is then used to calculate the void ratio. Also, soil properties such as particle size distribution, void ratios, and soil weights vary somewhat over even relatively limited distances (including areas identified as “uniform deposits”). Commonly for foundation studies at building sites, representative unit weights are selected on the basis of values determined from tested soil samples (samples obtained from borings, test pits, etc.) and assumed for areas between locations of known conditions (borings, etc.). Because of the various practical aspects, the effort to make highly accurate determinations of submerged soil weights is seldom undertaken when studies and designs are done. Instead satisfactory estimates, which can be made from knowing a wet weight, are frequently utilized. For many soils, and fortunately for ease of computation, the submerged unit weight is on the order of half the wet soil unit weight above the water table (related to the relatively limited range of specific gravity values for particles and typical void ratios), see the Eqs. below; a notable exception to this condition is soils containing significant decomposed vegetation or organic material. For many practical applications, the effects from adopting the simplification are negligible (but where accuracy is required, the Eqs. above for γ_sub or ρ_sub should be used).