Analysis of Ground Deformation Caused by Subway Tunnel Excavation in Kunming

Research at home and abroad shows that subway excavation often causes soil stress loss, resulting in settlement deformation and horizontal displacement of stratum. Therefore, combined with the special engineering geological conditions in Kunming area, the foundation deformation caused by subway excavation is studied, so as to provide an important foundation for proposing the protection measures of surrounding buildings and buried pipelines and promoting the construction of subway.

Criteria definition for high-rise buildings foundations deformation limitation

The article presents an overview of the foundation deformation limitation for buildings and structures. Information from main research, domestic and international construction codes is given. For high-rise buildings foundations deformation limits evaluation was done by analyzing architectural, technological, and structural requirements for high-rise buildings deformations and an estimation of a probable stochastic component of a non-uniform deformation which is related to statistically non-uniform of base soil. Statistical non-uniformity of base soil was modelled by the use of a simplified deterministic method. Defined criteria for high-rise building foundation deformation limitation can be used in future research.

Analysis of methods for analytical calculation of foundation settlement in time

Currently, there exist three main methods for calculating foundation settlement: the method of linearly compressible layer (introduced by Prof. K. E. Egorov), the method of layer-by-layer summation (described in SP 22.13330.2016), and the method of one-dimension virgin compression (a special case of the equivalent layer method introduced by Prof. N. A. Tsytovich). All the above-mentioned methods for calculating foundation settlement are based on the linear dependence of deformations on stresses. The principal differences between these methods are in taking the account of natural soil stress from its own weight, the technique of assessing the compressible soil strata and evaluating the distribution of stress in depth from external pressure. In the practice of bases and foundations design, the layer-by-layer summation method is considered to be the most highly reputable and widely used. It should be noted that each method was initially developed to solve some specific problem. However, not every engineer at present knows the limits of a particular method application for calculating foundation deformation. The article presents calculations of the non-linear settlement development in the foundation performed by various methods. Comparison with actual deformations is made based on the results of long-term monitoring of foundation settlement of a well-known building in Saint Petersburg, and recommendations are offered regarding the applicability of the discussed methods.

An online monitoring technology of tower foundation deformation of transmission lines

In this article, an online monitoring technology applied to transmission line towers is proposed to overcome the problems that the foundation deformation is difficult to find in the mining area, river, hillside, and other special areas. The measurement of the stress or the strain caused by the tower foundation deformation are rarely issued, though the tower status can be possibly assessed by the stress or the strain. A new online monitoring technology of tower foundation deformation of transmission lines is developed which consists of three parts. In the first part, the stress or the strain of the key elements is effectively analyzed under the different deformations such as foundation settlement, inclination, and side-slip with the tower finite element model built and the wind load and ice load applied on the tower. In the second part, the experimental platform of tower stress tests is set up, and the internal relations between the stress variation and the tower foundation deformation are determined. In the third part, the online monitoring technology of tower foundation deformation of transmission lines is developed based on fiber Bragg grating stress sensor and successfully applied in Jibei power grid in China. The results show that all the monitored stresses fluctuating with the wind speed are small in case that the condition of tower foundation is normal; on the contrary, the corresponding stresses will change greatly.