Soil Mechanics and Foundation Engineering最新文献

The article deals with the issues of an integrated approach to the implementation of geotechnical monitoring in complex engineering and geological conditions, taking into account construction in urban areas. In the example of a particular case of construction, it is shown that an important element of integrated geotechnical monitoring is the mandatory implementation of an engineering–geological forecast, including the calculation of the zone of influence of the object under construction and predictive calculations of the stability of surrounding buildings and structures, taking into account the obtained observational data with the obligatory use of several proven geotechnical programs and calculation methods. Integrated geotechnical monitoring should include several independent measuring and controlled systems, which should complement each other and ensure structural safety at all stages of construction and operation of the structure.

The article considers the temperature mode of the foundation of a building constructed on frozen soils according to the first principle without a ventilated underground using deep cooling with seasonal cooling devices (SCD) located in the centre of the building in a channel cooled by outside air. The results of numerical calculations were compared depending on the SCD arrangement methods: along the contour or in the centre of the building in a channel. It is shown that in the second case, the cooling efficiency and stability of the temperature mode of the base are significantly increased due to the stabilization of the annual temperature mode of the base upper layers. As a result, it becomes possible to use a foundation slab that transfers the load to frozen soils.

Internal erosion plays a significant role in the failure of earth structures. In this paper, the fine particle elimination method is used, and a series of triaxial consolidated undrained shear tests is conducted to investigate the evolution of undrained mechanical characteristics of soils due to internal erosion. The result indicates that the soil specimen with a larger loss rate of fine particles exhibits a lower undrained peak strength and lower undrained peak friction angle; the undrained peak strength increases with increasing confining pressure, and the initial relative density has a complex effect on the undrained peak strength and the undrained peak friction angle. Finally, the Mohr-Coulomb failure criterion is modified to predict the total failure shear stress of soils subjected to erosion.

Accuracy of numerical simulations of seismic response of soil slopes is influenced by the choice of boundary conditions. We used a finite element model, field records of ground motion, and two sets of generalized slope models to examine slope dynamics and identify optimal dimensions for the leading and trailing edges of slope models. To avoid superposition of seismic waves reflected by model boundaries, our results show that the length of the leading edge of the model should exceed two times slope height and the length of the trailing edge should exceed four times slope height. These dimensions would ensure the accuracy of simulation results. The difference between the seismic safety factor for a slope with viscoelastic boundaries and that for a slope with remote fixed boundaries is 0.02, which validates the applicability of remote fixed boundaries to analyses of slope seismic stability.

Considering the characteristics of fuzziness and randomness of shield tunnel face instability, normal cloud theory is introduced to establish an instability prediction model of the shield tunnel face based on the normal cloud-PSM (Product Scale Method). Geological, environmental, and tunnel influence factors are selected to set up a comprehensive evaluation index system. A three-dimensional numerical model is brought to determine the grading degree of each quantitative index. Then, the determination degree of the corresponding evaluation grade under each influencing factor is calculated using the normal cloud model. Finally, the product scale method is used to determine the index weight, calculate the comprehensive determination degree, and ascertain the instability risk level of the shield tunnel face according to the maximum membership degree principle. The prediction model is applied to predict the stability of the tunnel face of Chengdu Metro Line 18. The results of the instability prediction model of the shield tunnel face are essentially consistent with those of the fuzzy evaluation method and neural network method. The prediction results are also in good agreement with the real-world results. The prediction model should provide a new approach to the stability prediction of the shield tunnel face in the future.