On the Stress-strain Response Mechanism of Karst Foundation of Highway Bridges
Guizhou expressway bridges are featured by large span,high height and high load.In order to study the complex karst foundation failure mode of expressway bridges in karst areas,the discrete element numerical simulation method is used to simulate the stress-strain response mechanism of bridge karst foundation under the phenomena of series dissolution and olecranon rock.The project takes the cross dissolution phenomenon of the 4c-2pile foundation on the left side of the Bajiaowan Extra Large Bridge in the second section of the Tongxin Expressway and the 6-0 olecranon rock phenomenon on the right side of the Pipaodong Bridge as case studies.By using an active sonar system to detect the spatial position and distribution of karst under the bridge pile foundation,and using the discrete element method for mathematical modeling,the PFC particle flow software is used to simulate and analyze the strain stress response mechanism during the loading process.Finally,the structural approximation analysis method is used to verify and analyze the simulation results.Analysis results show that under the condition of two karst caves with heights of 0.62 m and 1.03 m distributed at 0.68 m and 1.73 m respectively at the bottom of the pile of the Bajiaowan Grand Bridge,the foundation will exhibit an overall failure mode of compression uplift and fragmentation under the design load of 2 7000 kN.When the bottom of the 6-0 pile on the right side of the Loquat Cave Bridge is exposed to the phenomenon of eagle beak rock at the bottom of the pile,under the design load of 18 000 kN,there will be local shear failure modes such as ground layer compression fragmentation and uneven settlement of the pile foundation,leading to foundation failure and instability.According to the structural approximation analysis method,although the thickness to span ratio of the two rock cave chambers at the construction site is greater than 0.5,which meets the theoretical requirements,their bending and shear resistance calculations have not passed.Therefore,it is determined that the foundation is unstable under the design load of the bridge.It has provided data support and decision-making basis for the karst foundation treatment of Tongxin Expressway through simulation analysis and theoretical calculation analysis conclusions.
bridge pile foundationkarst foundationseries dissolution phenomenoneagle beak rock phenomenonnumerical simulation
万方数据
维普
