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The Lanolin 750 kV electrical transmission line traverses more than 102.86 km through seasonally frozen regions, causing many engineering problems for transmission tower foundations. In this work, physical models of reinforced concrete independent foundations in soils with different frost heave grades were used to simulate the frost heaving performance in seasonally frozen alpine regions. The test results were used to evaluate the tangential frost heaving force calculated based on different specifications. The results showed that the tangential frost heaving force and frozen depth increased with the temperature decrease. Moderately frost-susceptible soils also increased the tangential frost heaving force and frozen depth. Based on technical standards, the main differences between the calculated and the test values were the variable load component and effective frozen depth coefficients. Correcting the coefficient values resulted in a closer agreement between the test and the calculation results. [ABSTRACT FROM AUTHOR]

The Lanlin 750-kV electrical transmission line is 162.45 km long and traverses more than 3.27 km in highly frost-susceptible soil in Lintao County, China, possibly inducing several engineering problems related to frozen soil in the transmission tower foundation. To study the frost heave characteristics of a reinforced concrete foundation in a seasonally frozen alpine region, in this study, physical model tests were performed on independent reinforced concrete foundations under highly frost-susceptible soil conditions and verified via numerical simulations. The temperature field evolution, tangential frost heaving force, unfrozen water content, and frost heave of highly frost-susceptible soil in an open water-refill environment and under dead load were investigated. The influences of surface temperature, overburden loads, and the buried depth of the groundwater level on the frost heave, tangential frost heaving force, and vertical displacement of the foundation were considered in the numerical simulations. Results showed that when the soil is close to the surface, the response of the temperature field is fast and the range of temperature variations is wide. The tangential frost heaving force was the largest in the middle and upper areas of the foundation, reaching a maximum value of 2.18 kN; moreover, the frozen depth and frost heave were 210.42 and 7.20 mm, respectively. The variation curves of the unfrozen water content were similar at all depths, and the replenished water content increased linearly with time. The numerical simulation results showed that the surface temperature considerably influences the frost heave deformation of the foundation, the dead load has a substantial restraining effect on the tangential frost heaving force and vertical displacement of the foundation, and the groundwater level influences the frost heaving ratio and the increment rate of frost heaving force. The fitting degree between the experimental and simulation results was good. Finally, measures for controlling frost heave to guide engineering practices were proposed based on the experimental study and numerical calculation. [ABSTRACT FROM AUTHOR]

Stone columns (SCs) can reduce the seismic response of pile-supported wharves in liquefiable sites. A series of parametric studies were conducted to investigate the influence of SC diameter, SC space ratio, SC permeability, and typical earthquake characteristics on the seismic response of pile-support wharves and to assess the SC retrofit effect. The ratio of the SC space and diameter is found to play an important role in reducing the deck displacement. Based on the experimental results, the damage state of a pile support can be restricted to a potentially tolerable level using SCs in different liquefiable sites. Preliminary design suggestions are proposed for improving the seismic response of pile-supported wharves in earthquake-prone regions. [ABSTRACT FROM AUTHOR]

The slope protection framework developed using recycled railway sleepers offers a novel sustainable solution for slope protection. However, this has been inadequately reported, and its force and deformation, its protective effect, and the bonding characteristics between sleepers are still unclear. The slope protection framework project of a recycled railway sleeper embankment slope on the Beijing–Tongliao railway was numerically analyzed using three typical recycled railway sleeper slope protection structures. The bearing properties and the slope stability of rectangular, rhombic, and herringbone framework structures were determined. The results show that the stress state, stress level, and failure mode of the three types of slope protection structures are similar on average. The slope protection skeleton's stress concentration position and failure area are all concentrated at the sleeper connection node at the slope base. The rectangular and rhombic framework structures have better stability than the herringbone framework. This study proposes applying a slope protection framework constructed entirely using recycled railway sleepers. Furthermore, it allows for proper disposal of recycled railway sleepers and a reduction in stone mining. [ABSTRACT FROM AUTHOR]

Featured Application: Potential applications of this work include predicting the stable stress and strain fields and analyzing the influence factors of frost heave force and deformation of soil surfaces after freezing processes. In analyzing frost heave, researchers often simplify the compressive modulus of freezing soil by considering it as a constant or only as a function of temperature. However, it is a critical parameter characterizing the stress–strain behavior of soil and a variable that is influenced by many other parameters. Hence, herein several one-dimensional freezing experiments are conducted on silty clay in an open system subjected to multistage freezing by considering the compressive modulus as a variable. First, freezing soil under multistage freezing is divided into several layers according to the frozen fringe theory. Then, the correlation between the freezing rate and temperature gradient within each freezing soil layer is investigated. Takashi's equation for frost heave analysis is modified to extend its application conditions by replacing its freezing rate term with a temperature gradient term. A mechanical model for the stress–strain behavior of freezing soil under the action of frost heave is derived within the theoretical framework of nonlinear elasticity, in which a method for determining the compressive modulus of freezing soil with temperature gradient, overburden pressure, and cooling temperature variables is proposed. This study further enhances our understanding of the typical mechanical behavior of saturated freezing silty clay under frost heave action. [ABSTRACT FROM AUTHOR]

The geosynthetic-encased stone column (ESC) strategy has been extensively used for improving soft soils. However, no studies have been conducted to assess the use of ESCs to mitigate sand strata. In this study, three-dimensional finite element (FE) analyses were conducted to explore the mitigation of mildly sloped saturated sand strata using ESC approaches. We investigated the encasement effect in ESC remediation and the effect of the following important design parameters in reducing lateral ground deformation: the thickness, the tensile stiffness, and the permeability of the geosynthetic; the ESC diameter; and the distributed load at the stone column (SC) surface. The results showed that the ESC remediation reduced more lateral deformation, compared to the SC approach. The ground stiffening was also dramatically enhanced as the stiffness and thickness of the geosynthetic and the ESC diameter were increased, but the encased efficiency gradually decreased. The lateral ground displacement began to decrease significantly when the permeability of the geosynthetic exceeded 0.1 m/s. The larger surface load did not prevent soil liquefaction, but it produced significantly less displacements and virtually no permanent deformation. [ABSTRACT FROM AUTHOR]

Reductions in bleeding rates and bulk shrinkage of grouting repair materials comprise the key to solving the leakage of earth–rock dams. In this paper, an anti-seepage grouting material for earth–rock dam was developed by introducing mineral admixtures and graphene oxide (GO) nano sheets into low-cost clay–cement grouting materials and by adding polycarboxylate superplasticizers (PCs) to improve slurry viscosity. The experimental results show that the shear stress and viscosity of the slurry increase with the increase in GO concentration, and the slurry has a certain thixotropy. GO can provide a platform to promote the formation of hydration products and fill the pores of clay particles due to its high specific surface area and low volume; in this paper, the microstructure of clay–cement–graphene oxide (CCGO) grouting materials were improved. Therefore, the bleeding rate, bulk shrinkage rate, setting time and unconfined compressive strength (UCS) of the sample were macroscopically improved. In particular, the bleeding rate and bulk shrinkage rate were shown to be 0% when the content of GO reached 1.08 g/kg. Thus, the grouting anti-seepage and reinforcement performance of CCGO grouting materials were improved. [ABSTRACT FROM AUTHOR]

The failures of soil slopes during the construction of high-speed railway caused by the soil after the freeze–thaw (F–T) cycle and the subsequent threat to construction safety are critical issues. An appropriate constitutive model for soils accurately describing the deformation characteristics of soil slopes after the F–T cycle is very important. Few constitutive models of soils incorporate the F–T cycle, and the associated flow rule has always been employed in previous models, which results in an overestimation of the deformation of soil exposed to the F–T cycle. Generalized plasticity theory is widely used to predict the performance of geotechnical materials and is especially well adapted to deal with this type of generalized cyclic loading (such as a freeze–thaw cycle), and it overcomes the shortcomings of the associated flow rule that causes larger shear deformation. To this end, an elastoplastic model framework based on generalized plasticity theory with double yield surfaces for saturated soils subjected to F–T cycles was developed. Two types of plastic deformation mechanisms, i.e., plastic volumetric compression and plastic shear, were considered in this elastoplastic model. It was found that this model can accurately predict the mechanical behavior and deformation characteristics of saturated soils after F–T cycles. [ABSTRACT FROM AUTHOR]

Cutting slope failures occur frequently along the high-speed railways in Northeast China during the construction due to snowmelt infiltration. This study addresses this issue by applying a three-dimensional numerical model. The influence of the depth of accumulated snow (ds), daily temperature variation (ΔT), and freeze-thaw (F-T) cycles on the seepage field and stability of cutting slopes is discussed. The results demonstrate that water seepage due to snowmelt infiltration primarily extends through the ground surface by about 10 m. The deep-seated instability is likely to occur under a prolonged and highly accumulated infiltration, while shallow failure is associated with intense, short-duration snowmelt infiltration. The maximum degree of saturation (Sr) and pore-water pressure (PWP) values are observed at the slope toe. Increasing ds and ΔT increase the Sr and PWP due to snowmelt infiltration and thereby decreases cutting slope stability. Compared to the ds and ΔT, the F-T cycle is more likely to cause slope failure. In addition, the F-T cycle also induces the reduction of soil strength and the crack propagation. Overall, the conducted study provided useful help toward the process of safer design for cutting slope along the high-speed railway in seasonally cold regions. [ABSTRACT FROM AUTHOR]