The shutdown of earth pressure balance (EPB) shield tunneling in gravel stratum can easily lead to significant unexpected ground deformation. In order to study the response of gravel strata during shield shutdown and the characteristic change of soil state in the chamber, this paper establishes a coupled Eulerian-Lagrangian finite element method (CEL-FEM) coupling analysis model that reflects the interaction between the spoiled soil and gravel strata. The plastic flow parameters of CEL spoiled soil are calibrated using the slump method, and a quantitative relationship between the slump value, plastic flow parameters, equivalent coefficient of loosening, and excavation face support pressure is established. The reliability and applicability of CEL method in the simulation of shield shutdown are verified by the field measurements. Results show that: (1) The chamber's soil equivalent loose coefficient is inversely proportional to the soil slump value which is related to soil's plastic flow parameters. (2) The shield shutdown in gravel strata has a more significant impact on the deep strata displacement than on the surface. (3) During the shield shutdown stage, the chamber pressure should be dynamically adjusted based on the soil deformation characteristics, and an increase of 16% could result in a stable rebalance.

In order to study the squeezing effect of static press large-diameter single pile and piles group in layered soil, field tests of static press large-diameter pipe piles were carried out based on a project under construction, and numerical simulations of the squeezing effect of single piles and piles group were conducted using finite element software. It is shown that during the process of pile penetration, the pore water pressure in the soil surrounding the pile rapidly increases to a higher initial value. Subsequently, the excess pore pressure will rapidly dissipate and gradually stabilize. The simulated and measured values of pile top displacement show a pattern of larger displacement at the pile top when the pile is first penetrated, and smaller displacement at the pile top when the pile is penetrated later. The measured horizontal displacement of the soil layer at each observation point of the group of 7 piles showed a turning point at a depth of about 2.5 m and fluctuated with increasing depth. The measured displacement reached its maximum value between 25 and 30 m and then rapidly decreased. The finite element simulation results of squeezing effect of the group of 20 piles show that the squeezing effect around the pile is very obvious within the depth range of the pile length. The horizontal displacement of the soil below the pile length rapidly decreases, and the maximum horizontal displacement of the soil at different depths around the pile mainly occurs at the surface. In addition, the reasons for the errors between the finite element simulation values and the measured values were analyzed.

There has been limited research conducted to date on the role and significance of soil parameters in an unsaturated state on the amount of deformation and safety of reinforced deep urban excavations. This study investigates stress-deformations and static/pseudostatic safety factors against the general failure of an anchored deep excavated wall in an unsaturated soil deposit through two-dimensional finite-element modeling and limit equilibrium analysis, respectively. A suction-dependent elastic-plastic Mohr-Coulomb model is used in the analyses considering the effective stress approach in unsaturated soils. The results obtained from numerical modeling are validated against field monitoring data, including wall deformations and tensile forces in the anchors. A series of parametric studies are then performed assuming different groundwater levels, surcharge loads, and surcharge load distances from the wall crest to investigate their effects on the stability and deformation of the unsaturated soil excavation. Results are compared with those obtained from the corresponding routine analyses, in which the unsaturated state of the soil is not considered. The parametric study shows that the depth of the groundwater table is more influential on the results compared with the intensity and location of the surcharge load. The study demonstrates that unsaturated soil conditions result in a reduction of up to 37% in the maximum horizontal deformations of the excavation and increase the static and pseudostatic safety factors against general failure by 28% and 19%, respectively. In addition, taking unsaturated soil conditions into account during analysis leads to a decrease of up to 31% in the estimated tensile forces in the anchors. More importantly, it is shown that a more cost-effective stabilization plan can be developed for deep urban excavations by considering soil unsaturation effects, as demonstrated by comparing the results of the numerical analyses with the field data. Presenting a safe and economically feasible plan for stabilizing deep urban excavations is a significant challenge for geotechnical engineers. Traditionally, engineers have relied on classical methods that consider soil parameters under dry or saturated conditions. However, in practice, the soil above the water table is unsaturated, and its mechanical properties are greatly influenced by the saturation level. Contrary to common belief, rainfall or pipe leakage near an excavation site does not fully saturate the soil and eliminate suction effects. Previous studies have shown that percolation from rainfall or other factors does not completely infiltrate clay-rich soils, mainly affecting moisture content and suction at shallow depths. This study evaluates the stress-strain behavior and the factor of safety against sliding in a deep excavated wall in Tehran, Iran, by considering unsaturated soil parameters. Comparing the outcomes with conventional methodologies, the results demonstrate that incorporating unsaturated soil parameters provides more accurate results aligned with field observations. This approach also results in smaller displacements of the excavation wall and higher safety factors against wall sliding. Accordingly, incorporating unsaturated soil parameters ensures accurate safety assessments for urban excavation walls and enables the creation of cost-effective and optimized design suggestions.

This investigation focuses on the characterisation of the aerosol particle hygroscopicity. Aerosol particle optical properties were measured at Granada, Spain, during winter and spring seasons in 2013. Measured optical properties included particle light-absorption coefficient (sigma(ap)) and particle light-scattering coefficient (sigma(sp)) at dry conditions and at relative humidity (RH) of 85 +/- 10%. The scattering enhancement factor, f(RH = 85%), had a mean value of 1.5 +/- 0.2 and 1.6 +/- 0.3 for winter and spring campaigns, respectively. Cases of high scattering enhancement were more frequent during the spring campaign with 27% of the f(RH = 85%) values above 1.8, while during the winter campaign only 8% of the data were above 1.8. A Saharan dust event (SDE), which occurred during the spring campaign, was characterised by a predominance of large particles with low hygroscopicity. For the day when the SDE was more intense, a mean daily value of f(RH = 85%) = 1.3 +/- 0.2 was calculated. f(RH = 85%) diurnal cycle showed two minima during the morning and afternoon traffic rush hours due to the increase in non-hygroscopic particles such as black carbon and road dust. This was confirmed by small values of the single-scattering albedo and the scattering Angstrom exponent. A significant correlation between f(RH = 85%) and the fraction of particulate organic matter and sulphate was obtained. Finally, the impact of ambient RH in the aerosol radiative forcing was found to be very small due to the low ambient RH. For high RH values, the hygroscopic effect should be taken into account since the aerosol forcing efficiency changed from -13W/m(2) at dry conditions to -17W/m(2) at RH = 85%.