Analysis of Deep Foundation Pit Construction Monitoring in a Metro Station in Jinan City

Abstract

In order to study the deformation law of adjacent building structures, surface settlement, displacement of supporting piles, axial force and variation of water level during different excavation stages of deep excavation construction, the deep foundation pit project in the M₁ line of the Jinan Metro was used as the background, and the data from field measurement of excavation and support were analyzed. The results show that the horizontal displacement of the pile presented a pronounced “bow” shape with the excavation of the foundation pit. The maximum horizontal displacement of the pile appeared at one third of the top of the pile, with a maximum of 31.98 mm. The maximum value of monitored axial force was 3100 kN, which was much less than the control value of 6847 kN. The maximum axial force appeared on the second steel support. The axial force of the first reinforced concrete support rapidly increased with the time. It was considered that the initial bearing capacity of the concrete was low, so the axial force of the concrete support was smaller than the steel support. The strength and load-bearing capacity of concrete increased in the later period, which resulted in a rapid increase in axial force. At the same time, during the process of setting up or dismantling the support, the attention should be paid to the axial force change of the adjacent support to prevent the danger caused by the abrupt change of the axial force. The maximum settlement value of the building appeared at the two corners far from the foundation pit, with the value of 4.3 mm. When the constructions were 34 m away from the deep foundation pit, the impact of dewatering on the building was greater than that of the foundation pit excavation, and he effect of the dewatering on the variational soil texture in this area was different. The maximum angular variation of adjacent constructions was 1/16,050, which was less than the 1/5000 of the minimum angular variation. The foundation pit structure and building were in a safe state, and the layout of the supporting structure was reasonable.