The displacements between segment rings are highly likely to occur in concealed creep fault areas. The dislocation of ring joint easily leads to the crushing of concrete around the bolt hole, which will become a potential safety hazard during tunnel service. For this problem, a composite Tenon was designed to improve the interaction at ring joint. It is necessary to carry out theoretical research to reveal the mechanical property of the ring joint. In this paper, a constitutive model of the Tenon was proposed based on specimen tests and numerical models. And the mechanical characteristics of the ring joint were investigated through prototype experiment and numerical simulation. The research results show that the composite Tenon is a flexible structure that can avoid the hard extrusion between the Tenon and the segments. The Tenon also has obvious protection effect on bolt and concrete around the handhole, which reserves more bearing space for the ring joint. These advantages are more conducive to dealing with potential risks such as earthquake, cyclic train loads, tunnel convergence deformation and uneven soil settlement during operation. The paper provides a theoretical basis for the application and promotion of the composite Tenon structure in the tunnel engineering.

The widespread distribution of riprap in estuarine mudflats has brought significant challenges to the penetration construction of steel casings. To reveal the effects of casing length, diameter and wall thickness on the stress and deformation, as well as the deformation characteristics and mechanical behaviors of the steel casing during the sinking process, the paper utilizes finite element method to construct a three-dimensional numerical model of the collision between steel casings and riprap in mudflat. The research results indicate that longer steel casing has better crushing effect on the riprap, smoother deflection curve of the casing body and smaller deformation at the casing end under the same casing diameter and wall thickness conditions. Under the same casing length and wall thickness conditions, the steel casing with a larger diameter has a better crushing effect on the riprap and smaller deformation at the casing end. As the casing diameter increases, the stress values of S11 and S33 in the soil at the casing end gradually decrease, and the range of stress concentration gradually increases. This study can provide a theoretical basis for the design and construction of steel casings in the riprap environment of the mudflat near the estuaries.

Investigating the mechanical properties of sandy cobble strata is essential for optimizing the design and construction of urban tunnels, thereby controlling ground deformation and ensuring tunnel stability. This paper aims to comprehensively investigate the mechanical properties and energy characteristics of heterogeneous sandy cobble strata. Numerical simulations are employed to examine the stress-strain behavior and energy evolution mechanism in scenarios with and without interfaces between the soil matrix and blocks. Subsequent analysis focuses on elucidating the effects of the internal stochastic structures, which characterize heterogeneity, on the overall strength and energy characteristics. The results indicate that the presence of interfaces significantly compromises the overall strength, while exacerbating the occurrence of a tortuous plastic zone around blocks. The volumetric block proportion (VBP), which represents the volumetric content of cobbles, has a significant impact on the overall mechanical behaviour. In the context of high VBP, block sizes, counts and orientations play substantial roles. Finally, the discussion reveals that when blocks are modelled using the elastic model, the overall strength is significantly overestimated compared to the strain-softening and Mohr-Counlomb models, especially in scenarios with high VBP and in-situ stress. It provides an unsafe evaluation (i.e., overestimation) of tunnel stability.

Major flood propagation processes often cause instability and damage to the ancient waterfront city walls. To quantitatively reveal the impact of major floods on the stability of ancient city walls, this paper takes Lanxi's ancient city wall as a study object and constructs a numerical model to investigate the influence of the major flood process in 2017 on the wall stability and reveals the varying laws of its seepage, displacements, maximal shear stresses and safety factors with flood propagation time on the basis of flood level data, combining indoor experiments and field observations. The results show that flood level variations significantly affect the PWPs (pore water pressures) of the fillings behind the wall. During the flood period, the maximal horizontal and vertical displacements are mainly induced by soil extrusion and deformation, and the maximal shear stresses of the outer and inner wall also significantly increase. The changing rates of the wall's safety factors measurably exceed that of the flood level. The flood level variation range dramatically affects the safety factors when it changes near and above the wall foot. The minimum of the safety factors decreases with the increasing flood level falling rate when it drops near the wall foot at different rates. The ancient city wall usually does not experience serious instability under a single major flood. This study can provide a theoretical basis for the selection of reinforcement measures for flood control ancient city walls and the protection of ancient waterfront buildings.

The single scattering albedo is a significant parameter obtaining the magnitude and sign of radiative forcing of aerosols, whereas our understanding of single scattering albedo Angstrom exponent (SSAAE) is still limited, especially for black carbon (BC) particles with brown coating. This study employs the accurate multiple-sphere T-matrix method to numerically evaluate the influences of aerosol microphysics on the SSAAE of coated BC aggregates. The SSAAE of coated BC shows strong dependences on absorbing volume fraction of coating, shell/core ratio, and size distribution, whilst it generally exhibits weak sensitivities to BC fractal dimension, BC position inside coating, and coated volume fraction of BC. Higher SSAAE values are seen for coated BC with less absorbing volume fraction of coating, lower shell/core ratio, or smaller particle size. BC particles coated by brown carbon for various size distributions have a wide variation of SSAAE between 350 nm and 550 nm with a range of -0.95-0.48, while the SSAAE at larger wavelengths (between 550 nm and 700 nm) shows higher values. Our study reveals that BC with non-absorbing coating can show negative SSAAE for thick coating or large size, and BC with brown coating may exhibit positive SSAAE for thin coating or small-sized coated BC, indicating the limitation of separating brown carbon from black carbon with a criterion of negative SSAAE. (C) 2020 Elsevier Ltd. All rights reserved.