Cement mixing techniques are widely used to improve the mechanical properties of weak soils in geotechnical engineering. However, due to the influence of various factors such as material properties, mixing conditions, and curing conditions, cement-mixed soil exhibits pronounced spatial variability which is greater than that of natural soil deposits, introducing additional uncertainty into the measurement and evaluation of its unconfined compressive strength. The purpose of this study is to propose a novel framework that integrates image analysis with Bayesian approach to evaluate the unconfined compressive strength of cement-mixed soil. A portable scanner is used to capture high-quality digital images of cement-mixed soil specimens. Mixing Index (MI) is defined to effectively evaluate mixing quality of specimens. An equation describing the relationship between water cement ratio (W/C) and unconfined compressive strength (qu) is introduced to estimate the strength of uniform specimens. To estimate the strength of non-uniform specimens, the equation is developed by integrating MI with the strength of uniform specimens. The coefficients of equations are obtained using Bayesian approach and Markov Chain Monte Carlo (MCMC) method, which effectively estimating the strength of both uniform and non-uniform specimens, with coefficients of determination (R2) of 0.9858 and 0.8745, respectively. For each specimen, a distribution of estimated strength can be obtained rather than a single fixed estimate, providing a more comprehensive understanding of the variability in strength. Bayesian approach robustly quantifies uncertainties, while image analysis serves as a convenient and non-destructive method for strength evaluation, providing accurate method for optimizing the mechanical properties of cement-mixed soil.

An Ms 7.4 earthquake struck China Maduo County in 2021, and it was a typical strike-slip rupture earthquake with clear directionality. A near-fault bridge named the Yematan No.2 Bridge suffered severe seismic damage in the Maduo earthquake. To analyze the seismic damage mechanism of the Yematan No.2 Bridge, the detailed finite element model of the bridge upline and downline was established in this study. To analyze the coupled effects of soil liquefaction, traveling wave effects, and seismic inertial forces, and to make the numerical simulation results better reflect structural seismic responses under real-site liquefaction conditions, this paper proposes a simplified method for simulating ground motions in liquefiable sites. This method integrates key effects induced by liquefaction into the ground motion simulation process. The detailed finite element model of the bridge upline and downline was established in this study. Then, the near-fault seismic bedrock motion of three directional components was synthesized by using the velocity pulse method to simulate the low-frequency pulse component and the stochastic finite-fault method to simulate the high-frequency component. The seismic ground motion was inversely computed by the equivalent linear method, and the field residual displacement measurement was used to optimize the seismic ground motion amplitude. Furthermore, to study the soil liquefaction effect on the bridge seismic damage, a simplified model based on planar one-dimensional wave theory was employed, and the seismic ground motion on the soil liquefaction site was computed through the site transfer function by using the inverse Fourier transform. Finally, the bridge seismic response analysis was conducted under non-uniform seismic excitation to consider the seismic traveling wave effect. The results show that the bridge's severe seismic damage is caused by the following multiple factors: (i) the fault rupture directionality of the near-fault earthquake results in the significant girder displacement along the bridge; (ii) the differential displacements between the upline and downline are also attributed to the soil liquefaction effect; (iii) the seismic traveling wave effect of strong seismic motion exacerbates the bridge seismic damage.

Weak structural plane deformation is responsible for the non-uniform large deformation disasters in layered rock tunnels, resulting in steel arch distortion and secondary lining cracking. In this study, a servo biaxial testing system was employed to conduct physical modeling tests on layered rock tunnels with bedding planes of varying dip angles. The influence of structural anisotropy in layered rocks on the micro displacement and strain field of surrounding rocks was analyzed using digital image correlation (DIC) technology. The spatiotemporal evolution of non-uniform deformation of surrounding rocks was investigated, and numerical simulation was performed to verify the experimental results. The findings indicate that the displacement and strain field of the surrounding layered rocks are all maximized at the horizontal bedding planes and decrease linearly with the increasing dip angle. The failure of the layered surrounding rock with different dip angles occurs and extends along the bedding planes. Compressive strain failure occurs after excavation under high horizontal stress. This study provides significant theoretical support for the analysis, prediction, and control of non-uniform deformation of tunnel surrounding rocks. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Quantifying the magnitude and distribution of degree of saturation (Sr) S r ) in unsaturated soils is crucial to understand the grain-scale hydromechanical behavior, but it has been a major experimental challenge. This study proposes a new method to quantify the pore-water distribution non-uniformity, in terms of S r , based on threedimensional (3D) X-ray computed tomography images. The algorithm constructs vectors that consider the 3D spatial distribution of Sr r for each REV. A weighted water distribution tensor (G, G , characterizing the spatial distribution of S r ) was derived to calculate a scalar parameter A that represents the non-uniformity. Application of the algorithm on sand samples demonstrated that the Sr r distributions could be highly non-uniform at different drying states. The algorithm captured pore-water transport between the dilated and non-dilated zones of samples subjected to pre-peak shearing. The evolution of A with matric suction and axial strain showed potential in incorporating the pore-water distribution into microstructure-based constitutive models.

Soil salinity typically exhibits non-uniform distribution in the natural environment. However, how vertically non-uniform distribution of soil salinity in the root zone (VNDSR) regulated plant nitrogen metabolism is still largely elusive. This study aimed to investigate the impact of VNDSR on leaf Malondialdehyde (MDA) content, upper and lower root activity, leaf Na+/Ca2+ and Na+/K+, various tomato organs' nitrogen concentration (%) and natural abundance of nitrogen isotopes (delta N-15,parts per thousand), and nitrogen utilization efficiency of tomato plants. Four treatments were established, including the upper layer of the root zone having soil salinity levels of 1 parts per thousand, 1 parts per thousand, 2 parts per thousand, and 3 parts per thousand, while the corresponding lower layer of the root zone had soil salinity levels of 1 parts per thousand, 5 parts per thousand, 4 parts per thousand, and 3 parts per thousand, respectively, denoted as T-1:1, T-1:5, T-2:4, and T-3:3. The results showed that under the same average soil salinity conditions and compared to the treatment with uniform soil salinity distribution in the root zone (T-3:3), the VNDSR treatment (T-1:5) significantly reduced leaf MDA content (p < 0.01), Na+/Ca2+ (p < 0.01) and Na+/K+ (p < 0.01), and stem delta N-15 values (p < 0.05). Moreover, the VNDSR treatment (T-1:5) significantly increased the ratio of upper and lower root biomass-weighted root activity (p < 0.01), tomato fruit yield (p < 0.01), and nitrogen partial factor productivity (PFP, gg(-1), p < 0.01) compared to uniform salt distribution treatment (T-3:3). There were significant positive correlations (p < 0.05) between leaf delta N-15 values and Nitrogen Absorption Ratio (NAR, %, p < 0.05) and PFP (p < 0.05), indicating that under VNDSR, delta N-15 values can serve as an indicator that comprehensively reflects the information of plant nitrogen utilization efficiency. In conclusion, the VNDSR could mitigate the damage of salt stress to tomatoes, enhance plant nitrogen uptake and utilization efficiency, and promote the growth and development of tomatoes.

The longitudinal seismic response characteristics of a shallow-buried water-conveyance tunnel under non-uniform longitudinal subsurface geometry and obliquely incident SV-waves was studied using the numerical method, where the effect of the non-uniform longitudinal subsurface geometry due to the existence of a local one-sided rock mountain on the seismic response of the tunnel was focused on. Correspondingly, a large-scale three-dimensional (3D) finite-element model was established, where different incidence angles and incidence directions of the SV-wave were taken into consideration. Also, the non-linearity of soil and rock and the damage plastic of the concrete lining were incorporated. In addition, the wave field of the site and the acceleration response as well as damage of the tunnel were observed. The results revealed the following: (i) a local inclined subsurface geometry may focus an obliquely incident wave due to refraction or total reflection; (ii) a tunnel in a site adjacent to a rock mountain may exhibit a higher acceleration response than a tunnel in a homogeneous plain site; and (iii) damage in the tunnel in the site adjacent to a rock mountain may appear in multiple positions, and the effect of the incidence angle on the mode of compressive deformation and damage of the lining is of significance.

The Dynamic Hollow Cylinder Apparatus (DHCA) is renowned for its ability to subject soil samples to various cyclic stress paths, allowing for the investigation of the dynamic behavior of soils under complex cyclic loading conditions. This note explores the errors arising from the stress non-uniformity along the height of DHCA samples and examines their impact on the measured soil dynamic properties. After discussing the two globally used DHCA types, this study presents the stiffness and damping of sand derived from a set of Dynamic Hollow Cylinder experiments covering a wide range of dynamic stress paths and shear strain amplitudes. It is highlighted that the deviation of the results from established degradation models is primarily attributed to the errors associated with the stress non-uniformity, leading to up to a tenfold underestimation within the medium strain range. A simple correction to the shear stress amplitude calculation is proposed to minimize the impact of stress non-uniformity and improve the accuracy of the test results.

The corrosion-protection liner (CPL) technology consists of installing flexible plastic liners with anchoring studs inside existing pipelines and subsequently filling cement mortar to the gap between the waterproof liner and the pipeline. With the excellent chemical resistance, impermeability and fast construction speed, CPL provides an economical and environmentally friendly alternative for pipeline rehabilitation without large-scale excavation. However, the seismic performance of water supply pipelines after being retrofitted with CPL has not been well studied yet. In this study, a series of full-scale quasi-static experiments were firstly conducted on ductile-iron push-on joints before and after reinforcement with CPL to investigate the nonlinear behavior of the joints under longitudinal load and transverse bending. Simplified numerical models of straight pipelines with joints before and after retrofitting in the non-uniform site were then developed in the OpenSees platform, and incremental dynamic analysis (IDA) were performed with consideration of nonlinear soil-pipeline interaction. Twenty-eight pairs of ground motions with the peak ground velocities (PGV) collectively scaled from 200 mm/s to 3000 mm/s were used as inputs. Seismic fragility curves of the pipelines before and after retrofitting were developed with respect to the optimum intensity measure, PGV. It can be seen from the experimental results that the longitudinal load and bending moment capacity of the push-on joint increased about 400% and 20% after CPL reinforcement, respectively, and the joint opening and rotation decreased about 20% and 18% after retrofitting. Numerical results show that the CPL reinforced pipelines exhibit better seismic performance and CPL effectively reduces the failure probability of segmented pipelines under earthquake ground excitations.

The strength and deformation characteristics of compacted soils are typically evaluated using triaxial compression tests on specimens that are compacted relatively uniformly in a laboratory. Soil compacted in the field using vibration rollers is nonuniform in the vertical depth direction; this is because the gradient of the dry density and saturation degree in the depth direction of each compaction layer is large, owing to the distribution of the load transmitted from the contact surface. As a quality control method for earth-filling works, nondestructive inspection indices-such as the soil stiffness index-are applied in some cases, and the average value of the nonuniform compaction layers is measured. Further, unsaturated specimens, which were retrieved from the test fill yielded during field compaction tests, and specimens obtained via compaction using the same soil as that in the laboratory were prepared, and then triaxial compression tests were performed. Local displacement transducers were installed to obtain local deformation characteristics, based on the vertical depth of the specimen, which were then compared with the average deformation characteristics of the entire specimen. The results show that the local low-stiffness significantly affects the overall average; this makes it non-negligible because the specimen compacted in the field is nonuniform. However, because field-compacted soil has a local low-stiffness near the surface layer compared with laboratory-compacted soil, evaluations based on the nondestructive inspection of the surface layer may result in underestimations.