【摘要】 【目标】研究根键层数、位置、个数、长度、截面形式及倾斜角度等因素对根式沉井竖向承载特性的影响。【方法】以马鞍山长江大桥5~#根式沉井基础为原型设计了根式沉井1∶75缩尺模型，在自制多功能模型槽中开展了根式沉井竖向受荷室内模型试验，监测了根式沉井荷载-位移、井身内力及沉井周围的土体应力状态情况。【结果】相比3层根键沉井，5层、7层根键沉井的极限竖向承载力更高，并增大了沉井底部土体水平应力的分布范围；根键沿井身居中、靠下布置时，沉井的竖向承载力更高；同层布置根键数由4根增加至6根时，沉井的竖向承载力增加了23.09%,沉降减少了26.15%;根键长度由40 mm增加至50 mm时，沉井的承载力提高了10.27%;根键横截面形状对沉井的承载力影响较小；对比根键水平布置，根键向下倾斜15°布置时更利于控制沉井的沉降量。【结论】合理增加根键层数、长度、缩小同层根键径向间距，能够扩大根键对土体的影响范围，有效提升根式沉井基础的承载性能，并降低基础的沉降量；沿井身靠下布置根键时，底部土体反力大，土体对基础的支承效果更佳。研究成果可为根式沉井设计提供参考依据，推动根式沉井基础在桥梁建设中的广泛应用。更多还原

【Abstract】 [Objective] To study the influence of layer, position, number, length, cross-section, inclination angle of root keys on the root type caisson vertical bearing characteristics, a 1∶75 scale model of root type caisson was designed based on the 5~# root type caisson foundation of Maanshan Yangtze River Bridge. [Method] The vertical loading laboratory model tests for root type caisson were carried out in a self-made multifunction model box. The root type caisson vertical load-displacement, caisson internal force, and soil stress state around caisson were monitored. [Result] Compared with the 3-layer caisson, the 5-layer and 7-layer root type caissons have higher ultimate vertical bearing capacity. The horizontal stress distribution range of soil at caisson bottom increases. When the root keys are arranged along the center or bottom of caisson, the caisson vertical bearing capacity is higher. When the number of root keys at the same layer is increased from 4 to 6, the caisson vertical bearing capacity increases by 23.09%, and the settlement decreases by 26.15%. The caisson bearing capacity increases by 10.27%, when the root key length is increased from 40 mm to 50 mm. The cross-section shape of root key has little influence on the caisson bearing capacity. Compared with the root keys horizontal arrangement, the arrangement inclined down 15° is more conducive to controlling the caisson settlement. [Conclution] The influence range of root keys on soil will be expanded by reasonably increasing the number of root key layers and length, and reducing the radial spacing of root keys at same layer. It can also effectively improve the bearing capacity of root type caisson foundation, and reduce the foundation settlement. When the root keys are laid down along the caisson, the bottom soil has a good supporting effect on the caisson foundation. The study result can provide a reference for the root type caisson design, and promote the wide application of root type caisson foundation in bridge construction.更多还原