Calcareous sand

Table S.l. Skeletal composition of a calcareous sand from a grass bed. Ferry Reach, Bermuda. (After Pestana, 1977.)...

Figure 5.9. MgCC>3 content of magnesian calcite component of shoal-water calcareous sands. A. 161 samples compiled by Garrels and Wollast (1978) B. Samples of mid-depth bank sands (Agegian and Mackenzie, 1989.)...

The source materials for both the modern calcareous sands and young calcarenites of Bermuda are characterized by a complex metastable carbonate assemblage of skeletal aragonite, magnesian calcite, and calcite. The limestone... 

Figure 8.33. Porosity-age relationships for odlitic grainstones. Notice that although the average porosity of these calcareous sands does not change significantly for a million years, the older oolites exhibit a spread in porosity because of dissolution-precipitation events. (After Scholle and Halley, 1985.)...

The two-layered structure of the Uzunlarian deposits is also registered on the Caucasian coast. Here, they form a coarse-grained terrigenous (conglomerates and calcareous sands) accumulative cover of the fifth (55 m high) terrace. 

Fig. 4 Scheme of the bottom sediments of the Aral Sea [10]. (1) Sand (2) oolitic-calcareous sand (3) coarse silt (4) fine silt (5) clayey-calcareous mud (6) deltaic clayey mud of the northern bays and small Sea... 

Bottom sediments in the depressions of the Aral Sea are clayey-calcareous mud - a homogeneous mineral mass enriched with diatoms fmstules, with inclusions of hydrotroilite and pyrite. There are areas of oolitic calcareous sands along the eastern sea coast. 

Nonequilibrium transport of solutes through porous media occurs when ground-water velocities are sufficiently fast to prevent attainment of chemical and physical equilibrium. Chemical reactions in porous media often require days or weeks to reach equilibrium. For example. Fuller and Davis Q) reported that cadmium sorption by a calcareous sand was characterized by multiple reactions, including a recrystallization reaction that continued for a period of days. Sorption of oxyanions by metal oxyhydroxides often occurs at an initially rapid rate the rate then decreases until steady-state is achieved (2-4). Unless ground-water velocity in such a situation is extremely slow, nonequilibrium transport will occur. 

Jurassic 145 Oxford clay. Fuller s earth Limestone, gypsum, calcareous sands and grit, jet and lignite ... 

When the pile penetrates into the soil, the soil is compressed, deformed, and pushed laterally aside. The amplitude of the lateral push depends on the compressibility of the sand. The variation of Oe is linked to the pushing back of the sand, and hence to the compressibility. For the calcareous sands, the crushing of the grains is a major phenomenon. Under the great stresses imparted by driving. 

Variation of lateral pressure in sand during pile penetration (confining pressure 200 kPa). Jacked, closed-ended pile Driven, open-ended pile S, terrigenous sand C, shelly and coralline sand. (From Nauroy, J.F. and Le Tirant, R, Model tests of piles in calcareous sands. Offshore Engineering Practice, ASCE, pp. 356-369,1983. Reprinted with permission of ASCE.)... 

Skin friction was shown by Nauroy and Le Tirant (1983) to be less for calcareous sands as compared to siliceous sands. The skin friction available for calcareous materials decreased as the compressibility of the materials increased as shown in Figure 10.11. In addition, the skin friction of closed-ended model piles was also shown not to be greatly affected by the increasing confining pressure (Nauroy and Le Tirant, 1983). 

Datta, M., Gulhati, S. K., and Rao, G. V. (1979), Crushing of calcareous sands during shear. Offshore Technology Conference, Houston, TX, Technical Paper No. 3525, pp. 1459-1467. 

Nauroy, J. F. and Le Ttrant, P. (1983), Model tests of piles in calcareous sands. Offshore Engineering Practice, ASCE, p>p. 356-369. 

Nauroy, J. R, Brucy, F, and Le Tirant, P. (1985), Static and cyclic load tests on a drilled and grouted pile in calcareous sand, BOSS, pp. 577-587. 

Because of the complexity of geomaterials, various databases have been compiled to cross-validate the results of laboratory and in-situ tests, check the reasonableness of theoretical solutions, and allow the development of statistical correlative relationships. These may also be used to help identify problematic soils that offer special difficulties in construction and long-term performance of built infrastructure e.g., organic soils, fibrous peats, calcareous sands, collapsible soils, dispersive clays, loess, carbonates, and loose liquefiable sands and silts. 

Calcareous sand or shell sand is a liming material collected from some beaches where there is a high shell content. The neutrahsing value is lower than for ground limestone. It is a useful material in areas far removed from the limestone quarries. 

Penetration resistance for the SPT and CPT is considered to be reduced for calcareous sands or materials that are more crushable and compressible than typical soils (e.g. Robertson Campanella, 1983). Wehr (2005) and Lunne (2006) indicate how these difference may be quantified. 

Degradable soils such as weak rock and calcareous sand The silt or clay fraction will segregate during the discharge process and may form lenses in the fill 9.1.2... 

In practice, however, a less strict nomenclature is often used and both calcareous sand and carbonate sand are encountered in soil classification as a general description. 

For equivalent Relative Densities, the Cone Resistance measured in calcareous sand is less than in quartz sand because of the compressibility and crushing effects of the particles. Depending on the compressibility of the (calcareous) sand, compared with reference sand, a shell factor or cone correction factor of the order of 1.2 to 2.3 has to be used. For instance, in the case of an applicable shell factor of for instance 1.5, a specified Cone Resistance of q = 9 MPa may be reduced to = 9/1.5 = 6 MPa. 

The only correct way to find a good correlation in calcareous sand (different from the published reference sands) is to setup a calibration chamber test. Unfortunately this is a very time consuming and costly effort and is therefore most often not a realistic approach. 

Homoud, A.S. and Wehr, W. Experience of vibrocompaction in calcareous sand of UAE, Geotechnical and Geological Engineering, No. 24, 2006. 

Van Impe, W.F. et al. Cone resistance quartz vs calcareous sand, 2001. 

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