The infiltration rate and therefore the principal function of a sand based vertical flow constructed wetland (VFCW) is influenced by the content of suspended solids (SS) and chemical oxygen demand (COD) of the waste water supply. In this study there were three operating conditions defined as "No Clogging"; "Partly Clogging" and "Clogging". Investigations on 21 VFCWs approved analytical differences between these conditions. The content of SS and especially particles > 50 microm are considered to play a key role. These particles are of the same size as the pores in which seepage mainly occurs. Thus their potential for surface blocking is high. It is concluded that the construction and size of the primary settling has to ensure that the mean concentration of SS after settling does not exceed 100 mg l(-1). The results of this study indicate that the area of the VFCW should be designed for a maximum loading rate of 5 g m(-2) d(-1) and the COD load should not exceed 20 g m(-2) d(-1).

SUMMARYFragmentation plays an important role in a wide variety of industrial processes such as blasting, demolition, crushing, cutting, etc., in which one desires to cause fragmentation in the most efficient and controlled manner. Nevertheless, a consistent theoretical description of this process is not yet available. In this paper, we present a computational methodology to simulate both the behaviour and the fragmentation of quasi-brittle materials, such as rocks and concrete, under dynamic loadings. We consider that the fragmentation process is a natural extension of the fracture process. In order to describe the dynamic fracture process, a suitable phenomenological constitutive model is developed and implemented in a finite element code. Concerning the dynamic fragmentation, a general formulation of predicting the fragment size distribution is provided. This formulation is based on a post-processing analysis of the history of the material's thermodynamic state. The complete approach is then applied to the modelling of the fragmentation of chamber blasting tests of limestone cylindrical samples.

The fracture behavior of random chopped-strand, glass-fiber reinforced SMC composites was studied. Experiments were conducted on notched SMC-R50 composite plates subjected to inplane loading. Fracture mechanics analyses based on recently developed conservation laws of solid mechanics were performed to evaluate notch-tip stress intensities in the specimens. Fracture toughnesses, K IQ and K IIQ , of this material under individual mode-I and mode-II loading were determined. Fracture tests and subsequent analyses were also conducted on the notched SMC-R50 subjected to combined-mode loading. Mixed-mode fracture criteria were investigated for the random short-fiber composite. The suitability of the Whitney-Nuismer two-parameter model was also examined for determination of notched SMC composite strength.

Heavy metal input into roadside soils and effects of deicing salts are often discussed as separate environmental problems. However, a relationship between salt input and heavy metal mobility has already been detected in laboratory tests. During a 2-year field study, the soil solution of a roadside soil was continuously sampled. The results of soil solution analysis not only showed a strong rise in deicing-salt related sodium, calcium and chloride concentrations, but also high zinc and cadmium values in winter and spring. Additional laboratory tests confirmed the mobilizing effects of salt solution which contained NaCl and CaC12. Cation exchange and the formation of chlorocomplexes are discussed as the responsible mechanisms. ~~~~ ~ Schlagworter: StraBenrandboden, Streusalze, Schwermetalle, Mobilisierung, Bodenlosung, Cadmium, Zink Zusammenfassung: Bisher galten Streusalzbelastung und Schwermetalleintrag in StraBenrandboden als voneinander unabhangige Arten der Umweltbelastung. Jedoch konnten bereits in Laborversuchen Zusammenhange zwischen Salzeintrag und Schwermetallmobilisierung festgestellt werden. Im Rahmen einer etwa zweijahrigen Untersuchung wurde kontinuierlich die Bodenlosung am Rande einer Autobahn untersucht. Die Ergebnisse zeigten im Winter und Friihjahr nicht nur eine starke, streusalzbedingte Zunahme der Natrium-, Calcium-und Chloridkonzentrationen, sondern auch einen deutlichen Anstieg der Cadmium-und Zinkgehalte in der Bodenlosung. Erganzende Laborversuche bestatigten die mobilisierende Wirkung einer aus NaCl und CaC12 zusammengesetzten Streusalzlosung. Als verantwortlicher bodenchemischer Mechanismus wird Kationenaustausch und Chlorokomplexbildung diskutiert. ~ ~~ Acta hydrochun. hydrobiol. 21 (1993) 1, m-m 0 VCH Verlagsgesellschaft mbH, D-6940 Weinhem 1993 0323-4320/93/0104-0038 $ 05.00+.25/0 m Ada hydrochim. hydrobiol. 21 (1993) 1 -11, Technisch-Inhondelijk Deel-Afl.4.-'s-Gravenhage: Sdu uitgeverij. Netherlands, 1988.