This research covered an evaluation of the copper and cadmium concentrations in bottom sediments dredged from one of the ponds in Warsaw. The samples of sediments, soil, and plants were analyzed in terms of Cu and Cd content. The research concerned the heap of dredged bottom sediments from Wyścigi Pond, Warsaw, Poland. Two boreholes were made to obtain sediment cores with depths of A 162.5 cm and B 190.0 cm. The cores were divided into 10 sub-samples with a thickness of about 15–20 cm. A control sample of soil was taken from the horse racecourse several hundred meters away from the heap. The vegetation was sampled directly from the heap. The predominating plants were tested: Urtica dioica, Glechoma hederacea, Euonymus verrucosus, and Drepanocladus aduncus. A control sample of U. dioica taken outside of the heap was also tested. The commercial PHYTOTOXKIT microbiotest was applied to evaluate the influence of heavy metal-contaminated sediments (used as soil) on germination and growth of the chosen test plants. The analyses of cadmium and copper concentrations revealed that the metal concentration in sediments was diverse at different depths of sampling, probably reflecting their concentration in stored layers of sediments. Moreover, the metal content in core A was four to five times lower than that in core B, which reveals heterogeneity of the sediments in the tested heap. In core A, the copper concentration ranged from 4.7 to 13.4 mg/kg d.w. (average 8.06 ± 0.71 mg/kg d.w.), while in core B, it ranged from 9.2 to 82.1 mg/kg d.w. (average 38.56 ± 2.6 mg/kg d.w.). One of the results of the heavy metal presence in soils is their bioaccumulation in plants. Comparing plant growth, more intensive growth of roots was observed in the case of plants growing on the control (reference) soil than those growing on sediments. The intensive development of both primary and lateral roots was noticed. During this early growth, metal accumulation in plants occurred.

The factors that affect the coefficient of permeability for a given soil are particle size distribution (grading curve), void ratio, level of saturation, soil structure, and soil imperfections or discontinuities [1,2,3,4]. The coefficient of permeability increases significantly with increase in the void ratio. Uniformly graded soil has a higher coefficient of permeability than well-graded soil. Natural plastic soils are often stratified and include lenses of nonplastic permeable soils, resulting in much higher horizontal than vertical permeability. Imperfections such as root cavities, fissures, and cracks significantly increase the soil permeability.For these reasons many engineers prefer field test over laboratory tests to obtain the permeability of soils. The main disadvantage of laboratory permeability tests is the small size of the usually reconstructed sample. The errors of different laboratory permeability tests are widely discussed by Chapuis [4].There are many different formulae to predict the coefficient of permeability of soils [2, 3, 4], particularly nonplastic soils [3,4,6,7,10]. A century ago Hazen [3,4] developed an empirical formula for predicting the coefficient of permeability of loose saturated sand in the simple formwhere k is the coefficient of permeability (cm/sec), C H is the Hazen empirical coefficient, and d 10 is the particle size for which 10% of the soil mass is finer (cm). This formula is frequently used in engineering practice. The published values C H range from 1 to 1,000 [5]. The Hazen formula (1) applicability is limited to 0.01 cm < d 10 < 0.3 cm [5]. The Hazen empirical coefficient C H expresses the influence of the void ratio, uniformity, and other factors on perThe Hazen formula, Kozeny-Carman formula, Pavchich formula, and Shahabi et al. formulas were used to predict the coefficient of permeability of nonplastic soils and compared with laboratory tests performed for eight soils of different porosities. The best correlation was obtained when using the Shahabi et al. formula. Knowing the velocity of water flow in soils is very important for the verification of stability against hydraulic hive, internal erosion, and in the design of drains and walls. The flow of water in soils is almost always laminar, and the water velocity is proportional to the coefficient of permeability.

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This paper analyses the stress–strain behaviour of fibre-reinforced sand using the results obtained by drained triaxial compression tests presented in the literature. The general stress–plastic dilatancy equation of the Frictional State Concept has been used to describe the behaviour of fibre-reinforced sand for different shear phases. The behaviour of pure sand is taken as a reference for the behaviour of sand with added fibres. It is shown that the characteristic shear phases can only be determined when the relationships are used, which are very rarely demonstrated in the results of shear tests presented in the literature. It has been shown that tensile strains must occur in order to achieve the strengthening effect of fibre reinforcement. A reduction in the stiffness of the fibre–sand composite is observed in the absence of tensile strains below certain threshold values.

Organic soil is characterised by high compressibility and should be improved so that it can be used for construction. The use of every method of soil improvement requires knowledge of the compressibility parameters. One of these parameters is the constrained modulus. The constrained modulus can be determined using laboratory or in-situ tests. In this study, the constrained modulus of organic soil was determined using oedometer and piezocone tests (CPTU). The author analysed subsoil under an approximately 250 m section of a designed road in north-eastern Poland. The constrained modulus of organic soil sampled from four different depths was determined in oedometer tests. Piezocone tests were conducted at 18 points located every 15 m along the length of the section concerned. To determine the constrained modulus based on the cone resistance from CPTU tests, the knowledge of the α and αM coefficients is needed. For the tested soil, the optimal range of the α coefficient from 0.4 to 0.7 was determined. The αM coefficient ranged from 0.4 to 0.8. The value of the constrained modulus of organic soil obtained from the oedometer tests, depending on the effective stress, ranged from approximately 100 kPa to 400 kPa. The constrained modulus of the tested soil decreased with depth, which both research methods proved.

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Floating geosynthetic encased columns (GEC) are an increasingly popular method of strengthening weak subsoil. Design of floating columns is a difficult and not fully recognized issue. This paper treats the floating GEC column as a special kind of “pile” and its bearing capacity is calculated using five selected methods for calculating the bearing capacity of piles based on CPTU penetration tests. The calculations were done on the basis of insitu tests carried out on one of the sections of the Bargłów Kościelny bypass. The paper contains a comparison of the bearing capacities of floating GEC columns calculated with different methods based on CPTU penetration tests.