Geological conditions and supporting structures are critical factors influencing the deformation characteristics of deep excavations. This study investigates the deformation characteristics and corresponding control measures for typical deep excavations, focusing on a metro station excavation within a mixed soil-rock stratum in Guangzhou. Using field measurement data collected during the excavation phase, we perform a statistical analysis to examine the relationship between maximum deformation and various influencing factors, including excavation depth, spatial effects, and the insertion ratio of the support structure. Additionally, we explore the distribution of excavation deformations, the relationship between lateral and vertical displacements, and deformation modes, offering engineering recommendations for optimization. Our analysis shows that, due to significant variations in the thickness of soft soil layers in Guangzhou, the maximum lateral displacement of the support structures predominantly ranges from 15 to 30 mm, while vertical ground deformations range from 0.86 parts per thousand to 2.35 parts per thousand of the excavation depth. Increasing the insertion ratio of the support structures improves their stiffness and reduces surface settlement caused by excavation. However, when the base of the support structure is embedded in the load-bearing rock layer and the insertion ratio exceeds 0.25, further increases in the insertion ratio lead to diminishing returns in controlling surface settlement. Both vertical ground deformations and lateral displacements of the support structures are positively correlated with excavation depth, while negatively correlated with the length-to-width ratio, width-to-depth ratio, and insertion ratio of the excavation. Based on these findings, we propose construction measures to enhance the stability of deep excavations and protect adjacent structures.

The complex mechanical behaviours of steeply inclined and layered surrounding rock in strong and active fault zones result in control measures that cannot adapt to asymmetric squeezing tunnel and are still unsolved. Hence, the Yuntunbao Tunnel was taken as an example to study this issue based on geological survey and indoor and outdoor tests. The results showed that strong geological structures and abundant groundwater undoubtedly deteriorate the mechanical properties of rocks containing many water-sensitive minerals, approximately 45%. The stepwise growth of deformation characteristics before reaching the rock peak strength and the gradient to abrupt failure characteristics after reaching the rock peak strength are determined via triaxial cyclic and static load tests. According to field test results, the unilateral squeezing deformation is severe and greater than 1.5 m, the average extent of the excavation loosening zone is approximately 10 m, and the highest deformation rate reaches 12 cm/d. The gradual and sudden changes in tunnel deformation are demonstrated to be consistent with the postpeak deformation characteristics of layered rock in indoor tests. Moreover, the steel arch exhibits composite failure characteristics of bending and torsion. Finally, reliable and practical controlling measures are suggested, including the optimised three-bench excavation method with reserved core soil, advanced parallel pilot tunnel, long and short rock bolts, and large lock-foot anchor pipe. Compared with tunnel deformation before taking measures, the maximum convergence deformation is reduced from 2.7 to 0.9 m, and the bearing force of the primary support is also reasonable and stable.

This article discusses the design of reinforced concrete structures taking into account non-uniform soil conditions, as well as aspects of sustainable engineering. To achieve this, the soil-structure interaction was explicitly introduced into the numerical model of the investigated structure which meets serviceability and the ultimate limit state conditions defined in the relevant Eurocode standards. In the numerical experiment, non-uniform soil conditions, type of foundation (isolated footing, foundation plate), material parameters and size of the cross of the elements (columns and beams) were analysed. The introduced heterogeneous soil profiles, determined by defining a parametrised, in terms of mechanical properties, spatial model of the layered soil, resulted in nonuniform settlement of the investigated structure. A global analysis of the three-dimensional reinforced concrete structure was carried out taking into account geometric nonlinearity with imperfections and material nonlinearity with creep. The displacement maps of the structure and the risk of collapse due to nonuniform settlement were established. Furthermore, an environmental so called life cycle assessment was performed for each variant analysed of the investigated structure. The innovative nature of the research is based on a joint approach to the problem of soil-structure interaction and the assessment of the carbon footprint of reinforced concrete buildings. This made it possible to determine how the varying soil conditions and different types of foundation affect the amount of material consumed and the carbon footprint associated with the production of reinforced concrete structures.

The characteristics of expansive soil, such as overconsolidation, multi fissure and shrinkage cracking due to water expansion and water loss, are called hidden disasters by the geotechnical engineering community. Its damage mechanism has become an important technical problem that the underground space engineering must face and solve. The expansive soil is mainly distributed in the eastern region in Chengdu. According to the investigation, the soil collapse between the supporting piles often occurs in the construction of the deep foundation pit of the subway station in the eastern region, causing safety accidents such as personal injury or equipment damage. In this paper, taking the stability of soil between piles of deep foundation pit excavation and support piles of the East extension line station of phase II of Chengdu rail transit line 17 as the research object, the instability characteristics of soil between piles of deep foundation pit excavation and support piles of railway stations on expansive land in Chengdu area are systematically studied by means of field investigation, field measurement analysis, instability characteristics analysis and calculation and derivation of soil stability between piles, and the characteristics and causes of soil instability between piles of deep foundation pit excavation and support piles of railway stations on expansive land are proposed, and put forward prevention measures and suggestions.

With the expansion of engineering activities, numerous major projects are gradually emerging in frozen soil regions. However, due to the unique engineering properties of frozen soil, various frozen soil engineering di-sasters have occurred or accelerated under the conditions of global warming, posing a serious threat to the project operation, environmental and ecological protection, and humanity development. This paper summarizes the formation conditions of frozen soil engineering disasters from the perspectives of thermal, hydraulic, and mechanical factors based on existing research. The definition, development trend and characteristics of thawing disaster, frost heaving disaster and freeze-thaw disaster are generalized. The main prevention measures are summarized based on the thermal, hydraulic, and mechanical conditions that cause frozen soil engineering di-sasters. Research suggestions on frozen soil engineering disasters including the engineering disaster mechanism under the frozen soil degradation and multi-hazard risk assessment are proposed. It may provide some references for the harmonious coexistence and sustainable development of engineering construction and geological envi-ronment in frozen soil area.