Response of stone column-improved ground under c-ϕ soil embankment

Problems with stone column-supported embankments are often addressed considering the pure granular soil properties of the embankment material. In practice, however, the embankment material may contain a certain percentage of fines which makes the material c-ϕ in nature. In the present paper, experimental and 3D numerical studies are conducted to investigate the effect of the fines content present in the embankment soil on the response of a stone column-improved ground. The numerical study is carried out using the finite difference software package FLAC^3D. The time-dependent behavior of the improved soil is modeled. It is observed that an increase in the fines content in the embankment soil brings about a decrease in the stress concentration ratio and an increase in the vertical displacement and the pore pressure in the soft soil. However, the vertical displacement of the soft soil does not change significantly above a fines content of 20%. The lateral displacement of the stone column increases at the top with an increase in the fines content and the point of the maximum lateral displacement shifts in the downward direction. It is also observed that the differential settlement increases at the ground level as well as at the embankment top with an increase in the quantity of fines in the embankment soil. Thus, the critical height of the embankment (a height where no differential settlement occurs on the embankment surface) increases due to the increase in the fines content.     

Dimension stone for building façades: methodology for structural design

The importance of a careful selection of rocks used in building façade cladding is highlighted. A simple and viable methodology for the structural detailing of dimension stones and the verification of the global performance is presented based on a Strap software simulation. The results obtained proved the applicability of the proposed structural dimensioning methodology which represents an excellent simple tool for dimensioning rock slabs used for building façade cladding. The Strap software satisfactorily simulated the structural conditions of the stone slabs under the studied conditions, allowing the determination of alternative slab dimensions and the verification of the cladding strength at the support.     

Effect of freeze–thaw and thermal shock weathering on the physical and mechanical properties of an andesite stone

Natural stones are exposed to physical weathering due to freeze–thaw (F–T) and thermal shock (TS) when they are used as pavement, cladding and masonry material. In this study, the deterioration of andesite was investigated by determining the physical and mechanical properties of andesite samples after each 10 cycles of F–T and TS up to 50 cycles. It was found that the P-wave velocity, Schmidt hardness and compressive strength decrease to different extents with F–T and TS while porosity and water absorption increase with F–T cycles but decrease with TS cycles. The results showed that F–T has a more destructive effect on the studied material than TS, although abrasion loss measurements suggest that the effect on the surface of the material is greater with TS. An exponential model is proposed to predict the variation of material properties with F–T and TS cycles.     

Comparison of fibrous insulations – Cellulose and stone wool in terms of moisture properties resulting from condensation and ice formation

Cellulose fibres are often used as thermal insulation in buildings. The organic nature of cellulose fibres, however, makes the insulation sensitive to high moisture content. This study investigates the moisture performance of cellulose insulation when exposed to a subzero environment. The paper is focused on the condensation and freezing in the material and includes comparison with the authors previous studies on stone-wool insulation. While the used stone-wool samples were water-repellent due to resin binders, cellulose is a typical representative for hydrophilic thermal insulation to which any contact with water condensate can be crucial.Test specimens of loose-fill cellulose were placed in a special laboratory device providing high moisture load. During a period of 100 h the specimens were subjected to a continuous load of moisture at atmospheric conditions on one side while the other side of the specimen faced a surrounding temperature of 0, −10 and −20 °C and the laboratory tests were repeated three times for each set of the specific thermal conditions (T_i = +20 °C, T_e = 0, −10 and −20 °C). The results indicate that there are minor changes in the water vapour permeability of the specimens. The experimental data from the investigation is compared with a mathematical model that simulates moisture diffusivity of cellulose together with accumulation due to sorption and freezing, using the actual climatic data.     

Experimental weathering of marlstone from Přednı́ Kopanina (Czech Republic)—historical building stone of Prague

Romanesque builders favoured marlstones because of their easy workability. Unfortunately, this rock rapidly deteriorates when exposed to the external atmospheric conditions. Artificial weathering experiments were conducted on marlstone from Přednı́ Kopanina quarry near Prague (Czech Republic) in order to determine: (A) which weathering factor presents major danger to this rock type, and (B) which of the test methods provide the most reliable measure of the intensity of rock disintegration. Rock specimens prepared from fresh rock were subjected to standardized freeze–thaw cycles and salt crystallization tests, and to the accelerated weathering in climatic chamber using SO₂ and a combination of freeze–thaw and SO₂ cycles. Stone properties were evaluated by non-destructive and destructive techniques including ultrasonic velocity measurements, determination of water uptake by capillary action, mechanical testing, detailed porosimetric analysis and microscopic study.