Reinforcement Effects of Isolation Piles on the Adjacent Existing Tunnel in Building Construction

Abstract EN

Similar material model test and numerical simulation method were used to study the reinforcement effect of isolation piles on the existing shield tunnel structure in the adjacent building construction for analyzing foundation pit excavation and new building construction approaching existing shield tunnel engineering.

The numerical simulation orthogonal experiment was used to optimize four isolation pile parameters.

The conclusions were obtained as follows: (1) Isolation piles could share horizontal load of the soil at the rear side of the support structure and reduce horizontal displacement of the soil.

As a result, maximum horizontal displacement of the tunnel structure and differences in horizontal displacement between the tunnel structure roof and the floor after foundation pit excavation and building loading were decreased.

The horizontal displacement and torsional deformation of the tunnel structure toward the direction of the foundation pit were controlled, and the increase in internal forces of the transverse tunnel structure was also restrained.

(2) At the elevation above the tunnel roof, the increase in burial depth of the isolation pile top slightly affected the reinforcement effect on the tunnel structure.

The increase in burial depth of the isolation pile bottom could improve the reinforcement effect.

Thus, burial depth of the isolation pile bottom should be properly increased in the engineering practice.

The reduction in pile spacing could improve the reinforcement effect.

Accordingly, pile spacing should be properly selected in the engineering practice.

With the increase of diameter of the isolation pile, the reinforcement effect of isolation piles increased obviously.

(3) Pile diameter had the greatest influence on the reinforcement effect of isolation piles, followed by burial depth of the pile bottom, pile spacing, and burial depth of the pile top.

Orthogonal experiments indicated the following optimal parameter values: a pile diameter of 1.2 m, a burial depth of the pile bottom of 2H, a pile spacing of 1.6 m, and a burial depth of the pile top of 0.75Z.