Improved calculation of the rigidity of double-row piles and double-beam composite support and displacement analysis under different soil properties

Abstract

As a new type of cantilever-type supporting structure, the double-row pile supporting combination system can improve the overall rigidity to maintain the safety and stability of the side of the foundation pit. The case of a double-row pile foundation pit support project in the Wanquan District of Zhangjiakou is taken as an example. Based on the existing double-row pile crown beam stiffness coefficient calculation method, the effect coefficient of the crown beam and the coupling beam is introduced to optimize and improve the effect of the coupling beam and the crown beam. The results show that (1) in the calculation of the double-row pile structure, the common lateral restraint effect of the crown beam and the connecting beam on the double-row supporting piles should be considered, and the rigid connection of the crown beam and the connecting beam should be taken as a whole to improve the rigidity coefficient of the double beam lateral support of a rectangular double-row pile. (2) The combined stiffness of the double-beam combined support system has a greater impact on the displacement of the pile top, and the displacement under a combined stiffness of 40～50 MN/m are close to the observed value. The calculated length of the crown beam and the introduced crown beam and connecting beam effect coefficient have a great influence on the combined stiffness of the double-beam composite support system. The combined stiffness decreases with the increase of the calculated length, and increases with the decrease of the effect coefficient. (3) The lateral support stiffness of the double-row piles under the double-beam composite support system is affected by the difference between the vertical and lateral displacements of the front and rear piles. The maximum lateral displacement of the front and rear piles is affected by the friction angle of the soil, the cohesion and the proportional coefficient of the horizontal resistance of the soil. Changing the tensile strength will not affect the displacement and deformation of the double-row piles. There is a displacement inflection point below the buried depth of the foundation pit and within the scope of the pile bottom. The displacement at the inflection point is equal under different friction angles and different cohesive forces.

Keywords

• double-row supporting piles
• double-beam lateral support stiffness
• double-beam combined effect
• soil horizontal resistance ratio coefficient