温度应力对深基坑支护结构内力与变形的影响研究

Influence of temperature stress on internal force and deformation of retaining structures for deep excavations

通过对武汉某基坑的地连墙加钢筋混凝土内支撑结构的应力、变形监测,详细分析了温度应力对内支撑杆件轴力和支护结构变形的影响规律,研究表明,当温度从30℃增加到37℃时,内支撑的轴力增幅达41%,冠梁水平位移有较明显的降低;当温度降低时,冠梁顶水平位移增加,坑壁外侧土体的水平位移变化明显滞后于地连墙的位移变化,导致地连墙至边坡范围内土体出现大量裂缝。提出了降低温度应力对基坑施工影响的工程技术措施,以及施工期内温差较大者应将内支撑混凝土强度提高一个等级、考虑支护结构位移的影响宜适当减少支护结构位移允许值、支撑长度大于40 m时温度影响系数宜取1.2及未采取必要保温保湿措施时温度影响系数取1.4以上等建议。研究成果对于类似工程有重要的理论和实践意义。

The influence of temperature stress upon internal force and deformation of retaining and structures for deep excavations is analyzed by monitoring the foundation pit of Wuhan Changjiang Shipping Center. The results show that the axial force of bracing system is increased by 41% and the horizontal displacement of the crown beams is decreased obviously when the temperature increases from 30℃ to 37℃. When the temperature drops, the horizontal displacement of the top crown beams increases 17 mm, and that of the lateral soils outside the retaining wall significantly lags behind the displacement of concrete retaining wall, resulting in large crack in soils between the wall and the side ditch. Some construction and technical measures are put forward to reduce the effect of temperature stress, and concrete strength should be increased by one grade if large temperature difference occurs during construction period. It is suggested that the allowable values of retaining structures should be appropriately reduced considering the displacement of supporting structures, the temperature influence coefficient should be 1.2 when the supporting length is greater than 40 m, and it should be above 1.4 without necessary thermal insulation and moisturizing measures. This research has important theoretical and practical significance for similar projects.