Journal of Geotechnical and Geoenvironmental Engineering

The hemiball penetrometer is a geotechnical device developed to measure the property of surficial seabed sediments ($<0.5\mathrm{m}$), which is of most significance for pipeline design and for situations in which traditional site investigation methods face challenges in accurately characterizing the soil properties. This study developed a novel method to derive the axial frictional resistance along the pipeline through a simple scaling relationship from the torsional resistance measured by the hemiball penetrometer in situ. To achieve this, the undrained and drained torsional resistances of the hemiball for idealized conditions were theoretically explored using the plasticity theory and principles of critical state soil mechanics. The link between undrained and drained torsional resistances for the idealized conditions then was established. Calibrated against those theoretical solutions, coupled finite-element analyses were conducted to explore solutions for more-realistic real-life conditions and to study the effects of hemiball embedment:diameter ratio, initial strength profile, and consolidation after hemiball or pipe installation. Based on these analyses, a simple model using two scaling factors, the effective radius of the hemiball and the equivalent length of the pipe, was proposed to derive the pipe–soil interface friction from the measured torsional resistance of the hemiball. The method presented in this paper provides a simple yet powerful approach for interpretation of hemiball testing results, and is an important step toward the eventual application of the hemiball in deep-water pipeline engineering.

A considerable sudden settlement was discovered on the Esfarayen Earth-fill Dam surface near to the left abutment when the reservoir level rose to 51 m from the riverbed in April 2013. As a result, a detection process was prepared to comprehend the problem and relevant challenges required to consider devising an appropriate remedial work. For this purpose, the work was divided into three main parts: (1) analyzing the information gathered from the monitoring and surveillance plan, (2) performing a geotechnical site investigation to test the subsurface condition and the extent of the problem, and (3) finding the cause of the problem initiation by considering three aspects—the bedrock geological condition, material susceptibility, and three-dimensional numerical modeling. The outcomes from the different parts of the study categorized the problem as an internal erosion incident. The existence of an inadequate sealed crushed zone of a fault passing through the reservoir on the contact surface with the clay core was the major cause of the internal erosion initiation. The water, appearing through this narrow crushed zone, applied additional hydrostatic pressure on the clay core, which depended on the reservoir level and had no influence on the stress distribution inside the dam. With the water pressure exceeding the minor principal total stress, a crack formed and extended with time, turning to a large void. Because of the high quality of the clay core material and its well-designed downstream filter, the internal erosion progression was concentrated on the core and directed to the upstream. When it reached the upstream filter, the filter entered into the core, and the material from the overlying part of the dam repeatedly dropped, resulting in a final settlement on the dam surface. The numerical modeling was successful in the determination of the approximate time of the internal erosion initiation by considering the past loading history of the dam and the influence of the existing defect.

A temperature rise in soils is usually accompanied by an increase in excess pore fluid pressure due to the differential thermal expansion coefficients of the pore fluid and soil particles. To model the transient behavior of this thermally induced excess pore fluid pressure in geotechnical problems, a coupled thermohydro-mechanical (THM) formulation was employed in this study, which accounts for the nonlinear temperature-dependent behavior of both the soil permeability and the thermal expansion coefficient of the pore fluid. Numerical analyses of validation exercises (for which an analytical solution exists), as well as of existing triaxial and centrifuge heating tests on Kaolin clay, were carried out for this research. The obtained numerical results exhibited good agreement with the analytical solution and experimental measurements respectively, demonstrating good capabilities of the applied numerical facilities and providing insights into the mechanism behind the observed evolution of the thermally induced pore fluid pressure. The numerical results further highlighted the importance of accounting for the temperature-dependent nature of the soil permeability and the thermal expansion coefficient of the pore fluid, commonly ignored in geotechnical numerical analysis.

This paper presents the results of a static load test (SLT) and two dynamic load tests (DLTs) performed on a closed-ended steel pipe pile (CEP) with an outer diameter $B=610\mathrm{mm}$ (24 in.) driven into a gravelly-sand soil profile. Cone penetration tests (CPTs), standard penetration tests (SPTs), and laboratory tests were performed to fully characterize the soil profile at the test site. The CEP was instrumented with 40 electrical-resistance and 24 vibrating-wire strain gauges. Locked-in residual loads were measured at the end of driving and used to correct the pile capacity components measured during the SLT. Load-settlement curve, load transfer curves, and unit shaft resistance profiles were obtained from the SLT data. Shaft and base resistances obtained from the SLT were compared with estimates from signal-matching analysis of DLT data and CPT-based pile design methods. The signal-matching analysis of the DLT data underpredicted the shaft and base resistance by a factor of two. The CPT-based pile design methods predicted the shaft resistance reasonably well; however, they overpredicted the base resistance by a factor of two. The overestimation by the CPT-based methods can be attributed to the presence of high gravel content near the pile base.

This paper presents the development of an improved plasticity model to define the combined vertical and horizontal capacity of suction caisson in sand under low vertical loads, conditions relevant for foundations of offshore wind turbines. Model tests following a variety of load paths were used to demonstrate the change of the shape of the yield surface as a function of the vertical load applied and to provide parameters for plasticity modelling. A new hardening law is proposed that accounts for capacity changes because of caisson lateral movement in addition to the vertical movements normally solely considered. An updated formulation for the yield surface is then presented based on a normalization by the new hardening parameter. The plastic model is subsequently validated by comparison with test results. The model can be used to assist in the prediction of the capacity of suction caisson under combined loading at low vertical loads.

Microbially induced carbonate precipitation (MICP) is increasingly being explored as a potential ground improvement mechanism, both for improved mechanical performance and groundwater control. However, the formation of a brittle cemented monolith will produce structures susceptible to chemical or physical deterioration over time, requiring potentially costly maintenance in the future. We present a demonstration of the potential for a simple and durable self-healing mechanism to be incorporated within the MICP process that allows the monolith to automatically respond to and heal damage. By selecting a bacterium capable of both causing MICP and surviving long periods and harsh conditions as a spore, it is demonstrated that such an organism can be entombed within calcium carbonate precipitates of its own making, survive in a senescent state, and ultimately germinate upon damage to the encapsulating precipitate matrix. The organism is then capable of producing further calcium carbonate to heal the damage. It has further been shown that this mechanism can be used to initially cement a mass of sand, survive damage and deterioration, and respond to restore the functionality of the stabilized mass, exhibiting the potential for such a system to provide “smart” autonomous stabilized soil structures that offer enhanced durability and reduced maintenance.

Small-scale physical model tests have been increasingly used to study the thermomechanical soil–pile interaction, but existing model piles are highly simplified and do not have representative thermal properties or the quasi-brittle mechanical behavior of RC. This study aims to overcome these shortcomings by presenting a new type of model RC. This consists of a mortar (plaster, sand, and water) with copper powder added to tune the mixture’s thermal properties, along with a steel reinforcing cage. Fine sand was used to represent geometrical scaling of the prototype aggregates to correctly capture the quasi-brittle structural response. Adding copper powder content of 6% (by volume) matched the coefficient of thermal expansion and thermal conductivity of prototype concrete without changing the axial and flexural properties of model piles. In $1g$ soil–structure interaction tests, the model pile was able to serve as an effective heat exchanger for transferring heat from a water-carrying pipe embedded within the mortar to the surrounding soil. The model RC exhibited cyclic pile head settlement due to repeated pile heating and cooling.

Low-field nuclear magnetic resonance has been shown to be sensitive to the chemical and physical changes in a porous medium caused by microbially induced calcium carbonate precipitation (MICP), confirming its potential for detection of MICP for subsurface engineering applications. This investigation used a 2-MHz rock core analyzer, measuring $T_2$ relaxation, in combination with scanning electron microscopy to characterize the daily chemical and physical changes occurring in various granular media including 1- and 0.5-mm soda lime glass beads and 1- and 0.45-mm quartz sand. An increase in $T_2$ time was observed in all of the granular media in accordance with MICP progression. An estimate of the surface relaxivity, $\rho$, was obtained for the silica glass, quartz sand, and mineral precipitate, which allowed for correlation between mineral precipitation surface coverage and $T_2$ relaxation time. The results indicated the potential for detailed in situ MICP progress monitoring during the early stages of the process by portable low-field nuclear magnetic resonance (NMR) devices.

This paper presents an evaluation of the long-term field performance of Farm-to-Market Road 2, the construction of which involved geosynthetic stabilization to address concerns related to the presence of expansive clays and associated environmental loads. A comprehensive study was conducted to quantify the benefits of geosynthetic stabilization in the performance of the roadway after having been subjected to 9 years of wet and dry season cycles. Control sections and seven design schemes (including various combinations of geosynthetic-stabilized base and lime-stabilized subbase courses) were incorporated in 32 test sections. Evaluation of the development of environmental longitudinal cracks over the 9-year period showed that the use of geosynthetics to stabilize the roadway base led to a significantly improved performance, as quantified based on the extent and length of environmental load–induced longitudinal cracks. The improvement, observed for all the geosynthetics considered in this study, was found to be more significant during dry seasons, which is when environmental longitudinal cracks develop. In addition, results from the field performance monitoring program revealed that lime stabilization of the subbase not only did not help but generally compromised the performance of road sections subjected to environmental loads.

Unconfined compressive strength ($q_{\mathrm{ucs}}$) and maximum shear modulus ($G_{\max }$), which are essential properties of grouted sands for quality control and stable design, exhibit a nonlinear behavior with curing time that makes it difficult to estimate the long-term $q_{\mathrm{ucs}}$ and/or $G_{\max }$. This study investigates the applicability of the hyperbolic model to capture the nonlinear development of $q_{\mathrm{ucs}}$ and $G_{\max }$ of grouted sands relative to curing time, with the ultimate goal of estimating the long-term $q_{\mathrm{ucs}}$. Three sands with varying particle sizes were grouted with microfine cement at three different water-to-cement ratios ($\mathrm{W}/\mathrm{C}=1$, 1.5, and 2), after which unconfined compression tests and bender element tests were performed according to curing time. The results of this study demonstrate that the hyperbolic model can effectively capture the time-dependent variations of both $q_{\mathrm{ucs}}$ and $G_{\max }$ of the tested grouted sands. Investigation of the hyperbolic coefficient $k$ of the tested materials reveals that the sand particle size and W/C affect the required curing time for completion of the hydration process, and relatively constant $G_{\max }$ values can be obtained at a relatively earlier curing time compared with $q_{\mathrm{ucs}}$. Finally, the direct relationship between $q_{\mathrm{ucs}}$ and $G_{\max }$ is investigated in this study.

A full-scale test was carried out to investigate the interactions between an energy pile and four traditional piles connected to the same overlying reinforced beam. A series of sensors was installed in the energy pile, surrounding soil, traditional piles, and beam to monitor their thermal and mechanical responses. The interactions between the energy pile and the traditional piles and concrete beam were analyzed. The results show that, when the average temperature of the energy pile increased by 20°C, a notable axial stress of $-4.4\mathrm{MPa}$ was induced at the top of the energy pile because of the interaction between the energy pile and the beam. Moreover, an additional axial load was observed in the four traditional piles because of their interactions with the energy pile, even though they were not subjected to thermal loading. Significant tensile axial loads of 820 and 663 kN were induced at the top of the two traditional piles adjacent to the energy pile, which were approximately five times larger than those induced at the top of the other two more distant traditional piles.

Thermally driven moisture and vapor transport in unsaturated soil under a thermal loading applied by underground structures affects the magnitude and distribution of matric suction. There is a lack of data about the temperature dependency on the hydraulic conductivity function (HCF). This study (1) developed and used a temperature-controllable soil column for directly and simultaneously measuring the temperature dependency on both the soil-water retention curve (SWRC) and HCF using the instantaneous profile method, and (2) conducted water-vapor heat transport analyses to illustrate the effects of temperature dependency of SWRC and HCF on matric suction. The measurements showed that for sand there was a suction threshold of 2 kPa, below which the hydraulic conductivity of sand heated to 50°C became higher than that at 20°C due to decreased water viscosity. Above this threshold, the hydraulic conductivity at 50°C became lower, by as much as an order of magnitude at 10 kPa suction, because of temperature-induced reduction of water-retention ability. A parametric study revealed that using SWRC or/and HCF obtained at 20°C overestimated the magnitude of suction for soil heated to a temperature higher than 20°C. The overestimations were greater when heating took place in drier soil. The effects of vapor transport were negligible during the early stage of heating, and became prominent only after 7–8 days of continuous constant heating of the soil, regardless of the amount of initial soil suction considered.