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Abstract—The response of sandy and clay subsurface soils, representing classes of non-cohesive and cohesive soils, during seismic motion of various intensities is analyzed based on the in situ observations—records by seismic vertical arrays of the Japanese strong motion network KiK-net. From a total of ~800 stations, five stations with sandy and five stations with clayey subsurface soils represented in the upper layers in their purest forms were selected for the analysis. For sandy and clayey stations, models of soil behavior during strong motion were constructed by the method of (Pavlenko and Irikura, 2003), showing vertical distributions of stresses and strains induced by strong motion in soil layers; and the behaviors were compared. Similar estimates of the amplification of seismic waves in sands and clays during weak motions and similar stress-strain relations describing the behavior of subsurface soils during moderate seismic motions are obtained. The liquefaction of sandy soils during strong motions (the 2011 Tohoku earthquake, Mw ~ 9.0) and the effects of extended seismic source (the directivity of seismic radiation) on the behavior of sandy and clayey soils and amplification of seismic waves are analyzed. Differences in the behavior of sandy and clayey soils are observed only during strong motions, namely, liquefaction occurs in sandy soils (when the groundwater level is about several meters from the surface), but never in clayey soils. [ABSTRACT FROM AUTHOR]

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]

The liquefaction phenomenon may originate in fine sandy - silty type of soils subjected to dynamic effects, low plasticity clays and even in soils with gravels based on the magnitude of applied acceleration. The mechanical or chemical soil improvement techniques have been used to prevent this problem. The mixing or grouting operations of sodium polyacrylate, which has a high-water absorption capacity, is one of the chemical soil improvement techniques. The frost behavior of this material, which turns into a gel form when react with the water in the environment, is not known in the permafrost areas. Within this purpose, sandy specimens including 5.00%, 10.00%, 15.00%, and 20.00% sodium polyacrylate gel as well as reference ones, were frozen at -20C° and unconfined compression tests were applied. Moreover, the tests were repeated for additional specimens containing 5.00% bentonite clay by weight. Although the unconfined compressive strength of all samples improved according to the increase in the amount of water with the gel content, about 14.00% lower values were obtained in specimens containing bentonite. On the other hand, the unit strain values of frozen samples without bentonite increased, while reduction observed in samples with bentonite. The viscous structure, that is in gel form inside the soil, dissipates volume increase during the freezing process and prevents the frost heave problem. However, the loss of bearing capacity should be considered in case of insufficient saturation in liquefaction sensitive sandy soils improved with sodium polyacrylate. [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]

Mechanical behaviour of the soil–structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermoactive structures, due to nonisothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and the soil–structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on the soil and soil–structure interface in a direct shear device at temperatures of 5, 22, and 60 °C. Fontainebleau sand and kaolin clay were used as proxies for sandy and clayey soils. The sandy soil was prepared in a dense state and the clayey soil was prepared in a normally consolidated state. Results show that the applied thermal variations have a negligible effect on the shear strength of the sand and sand–structure interface under CNL and CNS conditions, and the soil and soil–structure interface behaviour could be considered thermally independent. In clay samples, an increase in the temperature increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay–structure interface than in the clay samples. The adhesion of the clay–structure interface is less than the cohesion of the clay samples. [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 use of pre-emergent herbicides with prolonged residual effect on the soilis one of the factors that provide great efficiency in the control of the weeds. This study objected to evaluate the residual activity of the formulated mixture diuron + hexazinone + sulfometuron-methyl in different doses in soils of sandy and clayey textures. Two experiments were realized out, one for each soil, adopting the factorial scheme 2 x 8 + 1 with three repetitions. Two doses (0.605 + 0.170 + 0.014 and 1.072.07 + 0.302 + 0.025 kg ha-1 of diuron + hexazinone + respectively) at eight times (0, 20, 40, 60, 80, 100, 120 and 140 days, between the application of the formulated mixture and the bioindicator sowing) and another control without application. At 20 and 40 days after sowing of the bioindicator Cucumis sativus, phytotoxification was carried out. Using the non-linear log-logistic model, the t1/2 of the formulated mixture was determined for the two soils studied. In the soil of clay texture, t1/2 of 101 days was obtained, while for the sandy soil the t1/2 of the formulated mixture was of 52 days, for both doses. The prolonged residual effect on clayey soils may be an essential tool in the management of weeds in sugarcane. However, in sandy soils, smaller doses should be used because of the lower residual effect of the mixture and, consequently, avoid environmental contamination. [ABSTRACT FROM AUTHOR]

In order to study how shear strength and its change in unsaturated soils modified by hydrophobic agent, sandy soils hydrophobized by dimethyldichlorosilane (DMDCS) were prepared. The hydrophobic soils with different DMDCS volume by soil mass, water content and clay content were obtained respectively. Mixtures of sandy soils (DMDCS volume by soil mass were 2 mL:100 g and 3 mL:100 g, i.e., 2% and 3%, the same below) with 3%, 5%, 7%, 11% and 13% water content were prepared respectively. Meanwhile, the mixtures of clay and sandy soils (3% DMDCS) according to the clay mass fraction of 0, 5%, 10%, 15%, 20%, 25%, 30%, 40% and 50% were prepared respectively. Then the unsaturated direct shear tests were carried out by unsaturated direct shear apparatus. Four samples in each group were prepared under the normal pressure in 100, 200, 300 and 400 kPa, respectively. The horizontal shearing ratio was 0.8 mm/min and the shearing test lasted 6 min. The results showed that: 1) The mixtures of sandy soils and DMDCS presented extreme hydrophobicity. 2) The water repelling of mixtures of clay and sandy soils was affected by both DMDCS and clay content. The water repelling of mixtures was degraded with the increasing of clay content, and improved with the increasing of DMDCS volume by soil mass. 3) The Mohr-Coulomb strength criterion could be adopted to describe the shear strength of hydrophobic sandy soils with different DMDCS and water content. With the increasing of DMDCS volume by soil mass, the shear strength index of the hydrophobic soil was decreased to different extents. The cohesive force showed a steep-drop shape from soil without DMDCS addition to that with 1% DMDCS and a slow decline up to stabilize finally. The effect of DMDCS on the cohesive force of modified sandy soils was much greater than on the internal friction angle. The hydrophobic soils’ cohesion with the increasing of water content was decreased gradually, while the internal friction angle was increased firstly and decreased finally. The water content had a much effect on the shear strength of the hydrophobic sandy soils. The shear strength index were decreased with the increasing of DMDCS volume by soil mass: the cohesion was declined rapidly from 19.6 kPa (no DMDCS) to 10.4 kPa (1% DMDCS) and slowly from 10.4 kPa (1% DMDCS) to 9.3 kPa (3% DMDCS). The internal friction angle was declined slowly from 16.2° (no DMDCS) to 11.8° (3% DMDCS). The cohesion was decreased with the increasing of water content: the cohesion was declined from 15.5 kPa (3% water content) to 7.5 kPa (13% water content) with 2% DMDCS and from 15 kPa (3% water content) to 5.2 kPa (13% water content) with 3% DMDCS respectively; the internal friction angle was increased from 12.7° (3% water content) to 15.2° (11% water content) with 2% DMDCS and from 11.7° (3% water content) to 14.6° (7% water content) with 3% DMDCS, then decreased to 13.9° (13% water content) with 2% DMDCS and 11.9° (13% water content) with 3% DMDCS respectively. 4) The Mohr-Coulomb strength criterion could also be adopted to describe the shear strength of hydrophobic mixed soils with different clay content. The cohesion was increased remarkably with the increasing of clay content. The cohesion of sandy soils without clay was 9.3 kPa, then suddenly increased to 27.2 kPa and 55.1 kPa mixed with 5% and 50% clay mass fraction, respectively. The internal friction angle was increased from 12.1° (5% clay mass fraction) to 16.2° (15% clay mass fraction), and then decreased to 9.7° (50% clay mass fraction). All the analysis could be beneficial to analyze the shear strength of hydrophobized soils and apply in engineering. [ABSTRACT FROM AUTHOR]

• Thermal conductivity for frozen soil is higher than that of unfrozen soil. • Higher thermal conductivity of frozen and unfrozen soils at higher clay content. • Current models cannot predict correctly thermal conductivity of frozen sandy soil. Thermal conductivities of five sandy soils subjected to freezing-thawing and drying-wetting cycles were determined. Specimens were prepared at five different clay contents of 0, 5, 10, 15, 20% prior to compaction at the Proctor maximum dry density. Soil specimens were saturated prior to freezing-thawing and drying-wetting experiments. During a freezing-thawing cycle, soil's thermal conductivity and unfrozen water content were measured at different temperatures ranging from -3 °C to 0 °C. During a drying-wetting cycle, soil's thermal conductivity was measured at different water contents. The experimental results were then compared with predictions by two of the most appropriate existing models, namely De Vries's and Johansen's models, in order to provide insights into the effects of clay content on soil thermal conductivity at (saturated and unsaturated) unfrozen and frozen states. [ABSTRACT FROM AUTHOR]

Theoretical curves for different values of HT ht , 0.6, 0.8, and 1.0 are superimposed on the graph and can be seen to encapsulate the data. Yet, even without these separate curves, Wroth ([14]) noted that the parameter HT ht would track well with I ' i alone according to CSSM, and recommended the approximation HT ht (5) Graph: Fig. [Extracted from the article]

Scour is ubiquitous in offshore wind farms and threatens the stable state of the natural frequency of offshore wind turbines. The foundation of offshore wind turbines is a layered seabed, which mainly consists of clay, silt, and fine sand layers. However, little published literature can be found on the natural frequencies of monopiles in layered foundations with scour. The objective of this study was to reveal the influence of scour in layered foundations on the natural frequencies of monopoles and study its mechanism based on the dynamic characteristics of layered foundations. Therefore, based on an actual layered seabed, three typical layered foundations were established, and the first natural frequency of the monopile in terms of sensitivity to scour as well as the ability to resist continuous scour in the layered foundations were revealed. Moreover, the experimental results were analysed based on the stiffness and damping variations of the layered foundations under scour conditions. Importantly, a competitive relationship between the stiffness and damping of the layered foundations on the variation of the first natural frequency with scour was found and elaborated for the first time. The competitive relationship was influenced by the proportion of clay in the layered foundation. • The first natural frequencies of monopiles in different layered foundations present different responses to scour and different resistance to continuous scour. • The stiffness characteristics and damping characteristics of the layered foundations present a competitive relationship in the response of first natural frequency of monopile to scour. • The competition relationship between the stiffness characteristics and damping characteristics is influenced by the proportion of sandy soil and clay in the layered foundations. [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]

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]

• The mechanism in the interaction of the low water clays and jet grout is a combination of erosion and cutting. • Clays at low water content interact with jet pressure similar to silt and sandy soil. • An equation was proposed to estimate the diameter of the soilcrete column in low water content clays. • Optimum injection pressure for single-fluid jet grouting in clayey soil at low water content is 45 MJ/m. One drawback to the application of jet grouting for soil improvement is quality control, especially the determination of the diameter and strength of the column, which depends on the technical specifications of the injection and soil type. It has been reported that the initial water content of the clay effects the erosion of cohesive particles. The compressive strength and diameter of a soilcrete column in clay/sand at different jet grouting specifications have been well documented. However, the effect of the initial water content of clay on the performance of the jet grouting method has not been reported. Researchers have not proposed technical specifications for single-fluid jet grouting in remoulded clay with a low water content. The present study carried out 10 full-scale tests to analyse the effect of single-jet grouting specifications on the diameter and uniaxial compressive strength of soil-cement columns in a reclaimed area with low water content clay. The clay-jet grout interaction was evaluated using a microstructural approach and revealed that there is insufficient cohesion between the particles of remoulded clay. The mechanisms of interaction between the particles and the jet grouting is a combination of erosion and penetration of the grout into the soil and into air-filled cracks. In this case, it caused the particles to behave in a manner that is similar to that of silt and sandy soil. The efficiency of jet grouting in this type of soil was better than in clayey soil with a high water content. Thus, the equation previously used to estimate the diameter of the column has been modified by increasing the reference diameter from 50 to 60 cm for clayey soil with a low water content. The results show that an increase in the time interval and decrease in lifting step reduced the number of clayey clods in the core and increased the strength of the soil-cement. The maximum strength and diameter were achieved at an energy of 25 MJ/m with an optimum injection pressure of 45 MPa for single-fluid. [ABSTRACT FROM AUTHOR]