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The piezocone penetration test (CPTu) is a common geotechnical field test to evaluate soil properties. In interpreting the CPTu field measurements, soil drainage conditions are mostly considered completely drained or undrained; however, partial drainage conditions govern for such soils as silts or clayey sand mixtures. Previous studies show that neglecting partial drainage conditions causes incorrect estimation of soil geotechnical parameters. Most studies have been conducted using calibration chambers and centrifuge tests on clayey soils. Due to the complications in modeling the piezocone test, few numerical studies have been performed under partially drained conditions, especially on coarse-grained soils. Among the challenges of numerical modeling of CPTu, one can mention the difficulty of modeling soil structure in large strain mode and soil–water interaction behavior. In this paper, piezocone penetration tests were modeled using the advanced hypoplastic constitutive model and finite-element method. The behavior of Firoozkooh sandy soil under different drainage conditions and relative densities was analyzed. Then, the effect of cone penetration on the surrounding soils was discussed. It was shown that drainage conditions and the soil relative densities significantly affected the trend of variations in excess pore-water pressure (EPWP) generated around the piezocone. [ABSTRACT FROM AUTHOR]

Interactions between adjacent piled-raft foundations may induce additional settlement and cause the tilt of the structure. This case study investigates the long-term performance of a large piled-raft foundation system supporting high and heavy alumina solution storage tanks based on field measurements and three-dimensional (3D) numerical simulations. To properly consider the interactions among rafts, piles, and soils; the elastoplastic behavior of clayey and sandy soils; and the consolidation behavior of soil after construction, a 3D finite-difference code was utilized for the numerical modeling. Two undrained mechanical analyses were conducted to simulate the installation of foundations/tanks and the filling of alumina solution into the tanks, while two coupled hydromechanical analyses were performed to model the period between the two undrained stages and the stage after tank filling, respectively. The predictive capability of the numerical model was checked by comparing the simulation results first with single pile load test data and then with in situ settlement measurements at different locations of the piled-raft foundations. The long-term behavior of the piled-raft foundations was further investigated by analyzing various aspects including the axial force variation along the pile at different locations, the time-settlement relation at monitoring locations, the vertical effective stress increment and displacement of soil, and the differential settlement between monitoring locations. Based on the simulations, the tilt of the platform was mainly due to the superposition of additional stresses near the centerline of the two rows of piled-raft foundations. Finally, parametric studies were conducted to investigate the interactions among the piled-raft foundations at different pile length configurations. The results show that by properly increasing the length of the piles near the centerline of the two rows of piled-raft foundations, the differential settlement of the platforms can be mitigated. [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 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]

A new installation method for micropile is introduced, called driven grouted micropiles (DGMs), in which closed-end perforated steel pipes are driven to the refusal depth using a light hammer and grout is injected incrementally into the pipe using pneumatic packers. The increased bearing capacity and ease of construction of these micropiles recommend them over conventional micropiles. A total of 102 full-scale static loading tests were analyzed to evaluate the geotechnical performance of the DGMs in both sandy and clayey soil. The load–deformation curves were analyzed, and the ultimate bearing capacity of the DGMs was extracted using micropile failure criteria. The results show that, although existing micropile design manuals do not recommend consideration of the tip resistance of micropiles, the proposed DGM method recommends consideration of end bearing. The contribution of end bearing to the bearing capacity of the DGM is approximately 30%. In order to design a DGM that meets FHWA formulas for conventional micropiles, an incremental coefficient (λ = 1.3) is proposed to apply to the theoretical micropile diameter. Another incremental coefficient (η = 1.25) is proposed to apply to FHWA recommendations for bond strength that relate to the soil type. [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]

Compensation grouting is often employed as a mitigation technique to reduce the settlements induced by tunneling. The efficiency of compensation grouting, defined as the ratio of the volume of heave induced at the ground surface to the volume of injected grout, is strongly dependent on grout properties, injection characteristics, and soil properties. In clayey soils, site observations and laboratory tests show high values of compensation efficiency immediately after injection. However, the efficiency can decrease with time if positive excess pore-water pressures develop in the soil during the injection process. Conversely, in sandy soils, a loss of volume occurs because of pressure filtration of the grout during and soon after the injection process, which reduces the compensation efficiency. This paper describes an analytical model that can be used to evaluate the volume loss produced by pressure filtration of cement-bentonite grouts as a function of soil, grout, and injection parameters. The magnitude of pressure filtration is evaluated as the grout efficiency, which is given by the ratio of the volumes of the final grout body to the injected grout. Results show that the grout efficiency increases with decreasing soil permeability and with increasing grout bentonite content. The result of a grout injection test on a silty soil is back-analyzed using this approach in which the grout efficiency is first evaluated through the proposed filtration model and then used to calibrate a numerical simulation of the test. The good agreement between experimental data and computed results shows that prediction of the efficiency of compensation grouting can be improved using the proposed approach. [ABSTRACT FROM AUTHOR]

A new method of estimating the permeability of soils using an acoustic technique is proposed in this technical note. Biot’s coupled theory of mixtures from the mid-1950s, which addresses the relationship between the permeability of saturated soils and the characteristic frequency of elastic waves, is used. The characteristic frequency is determined from the attenuation versus frequency curves obtained by acoustic sweep tests. This study presents the experimental technique for measuring the characteristic frequency of soils and calculation procedure for estimating the permeability of sandy soils. This technical note holds discussion for silty or clayey soils. [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]

A viscoplastic cap model of the Perzyna type was developed for simulating high strain rate behaviors of soils. An associative viscous flow rule was used to represent time-dependent soil behaviors. The viscoplastic cap model was validated against experimental data from static and dynamic soil tests. The model was also compared with soil behaviors under creep and stress relaxation with good agreement. However, the model was unable to represent tertiary creep where strain softening became significant. The model was subsequently integrated into LS-DYNA for finite-element simulations of high strain rate behaviors of sandy and clayey soils in explosive tests. The significance of strain rate effect on the soil responses is presented herein. It is concluded that the viscoplastic cap model is adequate for simulations of soil behaviors under high strain rate loading, creep, and stress relaxation, covering a wide range of time-dependent problems. [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]

Focuses on a study that discussed a four-parameter model that can represent the shear modulus factors and damping coefficients for granular soils. Information on nonlinear soil behavior; Effect of confining pressure on modulus and damping; Experimental data on cohesionless soils; Details on the MIT-S1 stress soil model for clays and sands.