Methodology for evaluating the bearing capacity of a deep excavation barrette in complex geotechnical conditions in Hanoi

Introduction. At present, the rate of growth in the development of urbanisation processes in large cities is increasing rapidly every year. At the stage of preliminary design of pile foundations, an important part is to determine the bearing capacity of the pile. Barrettes are effective foundation structures, also for high-rise buildings on soft soils. In such conditions, long barrettes are designed. At the same time the used normative methods used of calculating the bearing capacity and settlement do not take into account the features of the stress-strain state of the foundation and the interaction with barrettes in the foundations of high-rise buildings with a developed underground part. Materials and methods. The task has been considered on the basis of the results of field testing with piles (static load method) with the calculation by the analytical method according to the strength characteristics of the soil foundation, described in the regulatory documents SP 24.13330.2011 “Pile Foundations”. A new calculation method is proposed, which is set out in Appendix D of the specified set o.rules, taking into account relevant factors, such as the relative position of piles in the ground, their length, pitch, etc. Results. A graph of the dependence of settlement on load was obtained based on the results of full-scale tests of barrettes with a limiting settlement of 40 mm. Analytical results are compared with field testing of a pile in difficult engineering and geological conditions in Hanoi, Vietnam. Conclusions. The conclusions obtained by the analytical method of calculating the bearing capacity of a single barrette in terms of strength characteristics, taking into account unloading on soft soils during the development of a deep pit, are quite close to the results of static field tests. These solutions can be applied to determine the bearing capacity of piles and barrettes on soft soils.