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The undrained shear strength (su) and overconsolidation ratio (OCR) of clayey soils are two key parameters that are frequently used in geotechnical engineering practice. In comparison to laboratory tests that are expensive and time-consuming, the fast evaluation of these parameters using the field piezocone penetration test (CPTu) is favorable. The available literature contains a number of correlations that have been suggested by several researchers to estimate the su and OCR from CPTu; however, these correlations were mostly empirical and were constants multiplied by CPTu measurements. In addition, these correlations were site-specific and provided rough estimations of these important parameters. In this paper, the process of a CPTu in clayey soils was modeled via finite-element (FE) formulations, and the predictions for excess pore water pressures (EPWPs) that were generated around the penetrating piezocone were elaborated on and used to develop two new relationships for the estimation of su and OCR from CPTu data. A major advantage of the proposed relationships is that they could be employed using CPTu measurements and no other information from laboratory experiments or calibrations with field benchmarks or reference values may be needed. The utilized simulation procedure and the proposed relationships were compared and validated with the laboratory and field measurements and the existing relationships in the literature. [ABSTRACT FROM AUTHOR]

This paper analytically investigates the postconstruction load-carrying capacity of a cast-in-place pile in clayey soil. The stress release induced by borehole excavation, the slurry supporting effects, and the dissipation of the negative excess pore-water pressure after construction, all of which have significant effects on the effective stresses of the soil around the pile, are the main concerns of this study, which aim to establish a method to reasonably evaluate the load-carrying capacity of a cast-in-place pile after construction. The stress release due to borehole excavation is modeled by cylindrical cavity contraction theory, which employs a K0-consolidated anisotropic modified Cam-clay (K0-AMCC) model to represent the mechanical behavior of the soil. Considering the dissipation of the negative excess pore pressure, the load-carrying capacity after construction is determined by the total stress method, with consideration of the three-dimensional strength of the soil adjacent to the pile. The proposed method was verified by finite-element (FE) numerical simulations. The results indicate that the soil properties and the factors involved in pile construction, such as the stress release due to borehole excavation, the slurry supporting effects, and the dissipation of negative excess pore-water pressure, have substantial influences on the postconstruction load-carrying capacity of the pile. [ABSTRACT FROM AUTHOR]

Soft marine deposits are widely distributed in the coastal region of China. The marine soft clays have high water content and high sensitivity, which shows high compressibility and low strength. The installation of precast piles for wind turbines over soft marine clay will generate high excess pore water pressure (EPWP) with very low dissipation rate, resulting in low bearing capacity and large postconstruction settlement, which will affect long-term stability. This study investigated the generation and dissipation of the EPWP correlated with the change in soil structure during the installation of pile foundations in a project of 100 MW wind-power generation in Lianyungang, Jiangsu, China. The results show that the marine soft clay soils feature strong natural structures based on the intrinsic compression concept. The EPWP decreases with increasing distance from the pile, whose influence reaches a distance of 6 m (about 10 times the pile side length). The structural strength of natural sedimentary clay has a remarkable impact on the generated EPWP. The dissipation rate of the EPWP is very slow in mucky clay with more than half the residual value after 30 days, which is mainly attributed to the sharp decline of consolidation coefficient induced by the disturbance of natural clay soils from pile driving. Moreover, hydraulic fracturing can well explain the dissipation characteristics of the EPWP in clay. This phenomenon is actually an ongoing process especially in marine soft clay soils with a strong cementation effect. [ABSTRACT FROM AUTHOR]

This paper presents as a discussion of "Performance Evaluation of a Highway Slope on Expansive Soil in Mississippi" by Mohammad Sadik Khan, Masoud Nobahar, Mike Stroud, Sean Ferguson, and John Ivoke. https://doi.org/10.1061/(ASCE)GM.1943-5622.0002240. Repairs to the failed section of the slope were undertaken a few months following the initial slope construction and were carried out by removing the failed soil and replacing it with a backfill that was less plastic, and therefore, not as swell-prone as the original soil. This approach versus the traditional approach when determining the factor of safety of slopes that used the limit-equilibrium method was considered more appropriate to account for the physical changes within the soil matrix that would occur during its wetting and drying cycles. [Extracted from the article]