Research Of Space Effect In Pit Retaining Gantilever Piles In Row

With the rapid development of construction of buildings and municipal facilities in Chinese cities, the number of projects with deep foundation pits has been increasing rapidly during the past decade and odd years and an extremely great wealth of experience has been accumulated. The status of deep foundation pit excavation technology, supporting types and its application were introduced in this paper, as well as successful and unsuccessful cases. The elastic, plastic and elastic-plastic methods caculating the pit retaining and protecting structure were also briefly described.Using the code caculating method, the coal ditch slope retaining engineering for Shijiazhuang heat and power plant was designed and the top beam's displacement of piles were measured. Strain-measuring gauges were set up in short side rows where are affected by space effect and in long side where are very close to pure plane, with seven gauges on the body, three gauges on the top beam in both soil-side and backside of piles. Further, reinforcing steel bar's strain was measured in different pit excavating status.According to the measured data, the influence of the pit space effect upon horizontal displacement on the top of the piles are analysed. The effect of pile's place upon top beam's internal forces by comparing the top beams' stress in short-side with that in the long-side and in the inner-side of short-side was also studied.Based on reinforing steel concrete structure theory and the internal force of retaining piles and top beams, that measured from actual engineering, the pile body's bending moment was caculated. Furthermore, the pulling force and the torque of top beam upon pile's body were worked out Thus, the influence of the space effect upon the interreaction between pile's body and top beam was worked out.By caculating the pulling force and torque of top beam upon pile's body and every spot's bending moment upside the pit bottom, the pile's bending moment caused by the active earth pressure was concluded, then, the space effect coefficient of piles in short side row was derived, further, the experimental result has been compared with the theory value.