Abstract In the open excavation works of foundation pit in urban area, a large number of internal support structures are used, among which the steel support end nodes are the key to controlling deformation and stability of the foundation pit. In order to improve the load-carrying mode of the support end, a high-foot-bolt & mould-package concrete fixed support end is developed. Its structural composition and characteristics are explained, and four sets of specimens are processed for indoor test. The mechanical properties of the specimens under axial and eccentric loads are studied. Failure mode, load-displacement curve, and load-strain curve of the specimens are obtained, and the elastic bearing capacity and the stiffness of the fixed support end are obtained. The test results indicate that: (1) the designed bearing capacity of the fixed support end is higher than 4 000 kN, exceeding the designed axial bearing capacity of ?609 steel support and meeting the requirements of strong node design. After yielding of the fixed support end, it has good plastic deformation capacity, with an ultimate bearing capacity larger than 6 500 kN; (2) The final failure modes of the specimen include buckling of the short connecting section of steel pipe, cracking of the mouldpackage concrete, and bending of the high-foot bolt. Increasing the compressive pre-stress and the strength of the mould-package concrete can improve the bearing capacity of the fixed support end; (3) The developed fixed support end has a simple structure and stable performance, which helps to improve the safety of foundation pit construction.
Abstract：
In the open excavation works of foundation pit in urban area, a large number of internal support structures are used, among which the steel support end nodes are the key to controlling deformation and stability of the foundation pit. In order to improve the load-carrying mode of the support end, a high-foot-bolt & mould-package concrete fixed support end is developed. Its structural composition and characteristics are explained, and four sets of specimens are processed for indoor test. The mechanical properties of the specimens under axial and eccentric loads are studied. Failure mode, load-displacement curve, and load-strain curve of the specimens are obtained, and the elastic bearing capacity and the stiffness of the fixed support end are obtained. The test results indicate that: (1) the designed bearing capacity of the fixed support end is higher than 4 000 kN, exceeding the designed axial bearing capacity of ?609 steel support and meeting the requirements of strong node design. After yielding of the fixed support end, it has good plastic deformation capacity, with an ultimate bearing capacity larger than 6 500 kN; (2) The final failure modes of the specimen include buckling of the short connecting section of steel pipe, cracking of the mouldpackage concrete, and bending of the high-foot bolt. Increasing the compressive pre-stress and the strength of the mould-package concrete can improve the bearing capacity of the fixed support end; (3) The developed fixed support end has a simple structure and stable performance, which helps to improve the safety of foundation pit construction.
GUO Caixia1,
2 LIU Wenjie2 ZHANG Mingju2 LI Pengfei 2 GAO Yunhao2 SHAN Yuhan2
.Experimental Study on Mechanical Properties of High-Foot-Bolt &Mould-Package Concrete Fixed Support Ends for Steel Support in Foundation Pit Works[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(5): 277-
2023, Vol. 60 