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In this paper, a constitutive model is presented to model the behavior of various soils (sand and clay) in different loading conditions and the minimum required parameters are obtained. Although some practical features (concepts) of the bounding surface framework and modified Cam-Clay have been employed in its formulations, the model is developed mainly based on the generalized plasticity framework. Moreover, some concepts such as dilatancy relation and loading history surface are redefined. Finally, the proposed constitutive model is evaluated using the experimental data related to two different sandy soils and three different clays under different loading conditions. Finally, it is concluded that the proposed constitutive model can easily be calibrated for various clayey and sandy soils. It can depict different behavioral aspects of these soils under different monotonic and cyclic loading conditions. [ABSTRACT FROM AUTHOR]

This paper addresses a soil bio-stabilization technique using bacterial enzyme-induced calcium carbonate precipitation (BEICP) as an alternative to previous conventional methods including microbial-induced carbonate precipitation and plant-derived enzyme-induced carbonate precipitation. The extracted urease enzyme of viable S. pasteurii was used as a biological source along with calcium chloride and urea to solidify sandy soil and silty sand soil. The bio-treated soil columns were subjected to freeze and thaw (F–T) cycling for a durability evaluation. Engineering properties of bio-cemented soil including unconfined compressive strength, calcium carbonate contents, moisture contents, porosity, permeability, and microstructure were examined before and after the F–T durations. It was found that although bio-stabilizer was able to increase a frost duration of soil, the F–T cycling significantly impacted on the compressive strength of bio-treated soil, due to a formation of microcracks. This investigation has revealed that the BEICP method provided a similar capacity in F–T resistance of soil as using the traditional Portland cement stabilizer, whereas the class F fly ash did not improve F–T durability of medium dense soil. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of coral reef sandy soil is significantly different from the sand and clay soils. Currently, Terzaghi's bearing capacity equation is still commonly applied to evaluate the bearing capacity of coral reef, while the calculation result is not consistent with the actual condition. Based on a port project in east Africa, plate loading test of the coral reef sandy soil has been conducted and the P-S curves are obtained, and the bearing capacity values obtained from the plate loading test results are compared with the calculated results based on the Terzaghi's bearing capacity equation. According to multiple linear regression and the optimal regression equation selected by the significance test, the modified Terzaghi foundation equation of bearing capacity in coral reef sandy soil area is proposed, and the modified Terzaghi foundation equation has important reference value for the calculating of the bearing capacity of the coral reef sandy soil foundations. [ABSTRACT FROM AUTHOR]

The physical and mechanical behavior of soil polymer composites tightly depends on the properties and structures of both soil and polymer. This study aims to investigate the effect of glass transition temperature as one of the most important characteristics of adhesive resins of acrylic polymers on the geotechnical behavior of soils that have not been fully covered by previous studies. To achieve that, three similar copolymers of methyl methacrylate-co-butyl acrylate with different glass-transition temperatures of 1°C, 33°C, and 51°C were synthesized, and two representative specimens of cohesive (kaolinite clay) and noncohesive (sand) soils were chosen to perform a full investigation of the consequential changes in the physical and mechanical behavior. A series of laboratory tests, including the Atterberg limits tests, the unconfined compressive strength tests, direct shear tests in soaked and unsoaked conditions, swelling tests, and odometer tests, were conducted on untreated and treated soils with synthesized polymers. The results showed a salient enhancement in the cohesion and the unconfined compressive strength value of both soils. However, the polymer with a glass-transition temperature near to ambient temperature led to a greater increase in the compressive and shear strength of stabilized soil among its peers. Samples treated with the polymer having the lowest glass transition temperature revealed a more compression index (i.e., obtained from odometer tests) and lower unconfined compressive strength. It is also observed that the swelling index and swelling pressure decreased marginally with increasing the glass transition temperature. [ABSTRACT FROM AUTHOR]

Wear and friction cause huge economic losses in the agriculture and mining industries. Wear simulations of working elements, materials, and surfaces that can reduce downtime and economic losses. This work proposes the use a cone penetration resistance measurement result as option to determine movement resistance of soil ripper tine by the discrete element method. It allows avoiding mechanical properties investigation of soil. Simulation made in sand and sandy clay helps to compare wear track of tine wear plates with actual wear. The actual wear was evaluated by 3D scanning of a soil ripper tine wear plates made from tungsten carbide and cobalt alloy and compared with simulated tines. Wear loss expressed as loss of area at the cross-section of tine wear plate. The maximum wear loss of scanned ripper wear plate at 0–150 mm working depth is 1.8% and simulated-in-sand and simulated-in-sandy-clay 1.2 and 1.7%. The maximum actual wear loss caused 57.9% wear loss of cross-section area at 150–204 mm working depth. Simulation in sand and simulation in sandy clay soil 6.9 and 9% caused by lower soil resistance than in field experiments. Simulations in sandy clay soil increased the draft force by 3.9 and 2.8 times that in the sand, at 0–200 mm depth, for tine parts to account for the stiffness fraction of sandy clay soil. As an alternative, tine wear evaluation is also suggested from shear energy values. Image 1 • Wear modelled by discrete element method. • Soil hardness simulation. • Wear model comparison with field experiments. • Evaluation of wear dependency with respect to working depth. [ABSTRACT FROM AUTHOR]

The laboratory and field test data on the response of piles under the combined action of vertical and lateral loads is rather limited. The current practice for design of piles is to consider the vertical and lateral loads independent of each other. This paper presents some results from three-dimensional finite-element analyses that show the significant influence of vertical loads on a pile’s lateral response. The analyses were performed in both homogeneous clayey soils and homogeneous sandy soils. The results have shown that the influence of vertical loads on the lateral response of piles is to significantly increase the capacity in sandy soils and marginally decrease the capacity in clayey soils. In general, it was found that the effect of vertical loads in sandy soils is significant even for long piles, which are as long as 30 times the pile width, while in the case of clayey soils, the effect is not significant for piles beyond a length of 15 times the width of the pile. The design bending moments in the laterally loaded piles were also found to be dependent on the level of vertical load on the piles. [ABSTRACT FROM AUTHOR]

The time-dependent behavior of soils has been investigated extensively through one-dimensional and triaxial test conditions. Most of the observations in literature have focused on the determination of the time-dependent behavior of clayey soils, whereas the reported experimental studies of granular materials are few. This paper presents an up-to-date review of the various observed time- and rate-dependent phenomena that are known to exist for both clay and sand. The description is carried out separately for creep, stress relaxation, rate dependency, and structuration in laboratory experiments. All of the above-mentioned phenomena are present in both sand and clay. The time-dependent phenomena are more pronounced in clay than sand. However, sand exhibits relatively large deformations at high confining pressures because of grain crushing. Furthermore, the review revealed an essential characteristic situation for soils. That is whether the time-dependent behavior can be characterized as isotach or nonisotach. It seems that the isotach behavior is adequate for describing the time effects in clays in most situations. But for sand, the isotach description is inadequate. Further, the phenomenon of structuration plays a role in both clay and sand. [ABSTRACT FROM AUTHOR]

Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena (creep, stress relaxation, and rate effects) observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part is a review of the empirical relations, which apply only to problems of specific boundary conditions and frequently involve natural time alone. The second part deals with different rheological models used for describing the viscous effects in the field of solid mechanics. The rheological models are typically developed for metals and steel but are, to some extent, used to characterize time effects in geomaterials. The third part is a review of constitutive laws that describe not only viscous effects but also the inviscid (rate-independent) behavior of soils, in principle, under any possible loading condition. Special attention is paid to elastoviscoplastic models that combine inviscid elastic and time-dependent plastic behavior. Various general elastoviscoplastic models can roughly be divided into two categories: Models based on the concept of overstress and models based on nonstationary flow surface theory. Although general in structure, both have shortcomings when used for modeling of soils. [ABSTRACT FROM AUTHOR]

This paper concerns a study of the influence of fines on the resistance to liquefaction of a clayey sand. The study is carried out using a triaxial apparatus on a reconstituted sand-clay mixture containing a low fraction of clay. After a description of the soil used in this study, the paper presents results of undrained compression tests together with cyclic liquefaction tests performed on soil samples containing different fractions of clay. Experimental results show that the increase in the fines content up to 15% reduces the resistance to liquefaction of the sand-clay mixture. This result is due to the role of fines in reducing the dilatant tendency of the clayey sand used in this study. [ABSTRACT FROM AUTHOR]