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| Experimental study on dynamic and bearing characteristics of part-screw pile composite foundations under train loads |
| GUAN Wei1，2，WU Honggang1，2，YU Shijiang3，WU Shugao3，ZHU Zhaorong2
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| (1. Key Laboratory of Karst Environment and Geological Hazards，Ministry of Land and Resources，Guizhou University，Guiyang，Guizhou 550025，China；2. Northwest Research Institute Co.，Ltd. of CREC，Lanzhou，Gansu 730070，China；
3. China Railway No.8 Engineering Group Co.，Ltd.，Chengdu，Sichuan 610036，China)
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Abstract The characteristics of dynamic strain，earth pressure and cumulative displacement of pile-soil system under multi-train operation mode were tested by laboratory model test of railway screw pile composite foundation under simulated train loads. The time-frequency characteristics of dynamic response of the screw pile-soil system under train load were analyzed，and the correlation of pile-soil deformation under different speeds was further discussed. Based on the linear fitting method，the empirical relationship between the pile-soil dynamic stress ratio and the train speed was established. Combined with the pile-soil load sharing relationship，the pile dynamic axial force and the pile side dynamic friction，the interaction relationship and loads transfer mechanism of screw pile-soil under train dynamic loads are revealed. The results show that：(1) under the train dynamic load，the deformation degree of a screw pile is greater than that of straight rod，especially at variable section. (2) Under the conditions of general speed，fast speed and high speed，the dominant frequencies are concentrated in 2–6 Hz，8–11 Hz and 14–16 Hz respectively. With the increase of train speed，the dominant frequency tends to the natural vibration frequency of the train，and the frequency band width decreases. (3) The dynamic characteristics of screw pile composite foundation are highly correlated with the speed of train operation. (4) Under the reinforcement of screw pile composite foundation，the critical velocity of railway foundation is about 280 km/h，which is 29.62% higher than that of ordinary pile foundation. (5) The faster the train speed is，the greater the effect of soil load on pile-soil composite foundation，while the less the effect of pile load on pile-soil composite foundation，resulting in the decrease of pile-soil synergistic effect. The research results have certain reference significance for the design optimization of railway screw pile composite foundation and the planning of train operation speed.
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2023, Vol. 42 
