车辆荷载对软土地区海底沉管隧道的影响分析

Analysis of the Impact of Vehicle Loads on Submerged Tunnels in Areas of Soft Soil

摘要:

假定软土地区海底沉管隧道地基土为Kelvin模型,车辆荷载是随时间变化的波动荷载形式,引入黏弹性地基梁模型,利用模态叠加法给出三种情况下沉管隧道的竖向位移、弯矩和地基反力的解答。结合天津海河沉管隧道工程实例,分析车辆速度、地基土模量对沉管隧道竖向位移及弯矩的影响。研究结果表明:车辆荷载引起的管段中点振动振幅达5 mm左右,振动周期为0.25 s;引起的管段中点弯矩为15 500 kN·m左右,且车速越大,管段振动一个周期所需时间越短,振动越剧烈,但对振动幅度及弯矩影响不大;地基土模量越大,振动幅度和弯矩越小,但对周期影响不大。

Abstract:

As unique underground structures, submerged tube tunnels have been subject to vehicle loads for long periods of time.As the loads change, the underwater tunnel will show cyclical changes in displacement, bending moment, and ground reaction force.These periodic changes represent a significant potential threat to the integrity of tunnel structures.The purpose of this study was to assess the impacts of vehicle load on those tunnels.The modal superposition method was used to analyze three characteristics of vertical displacement, bending moment, and ground reaction force in underwater tunnels.In this method, two conditions were assumed:(1)the underwater tunnel in soft soil areas is the foundation of the Kelvin model, and (2)vehicle loading is the fluctuation of load form changing with time.The impact of vehicle speed and the foundation soil modulus on the tunnel's vertical displacement and bending moment was analyzed.Using the Beam-On-Elastic-Foundation (BOEF) model, combined with data from the Tianjin Haihe River tunnel engineering, the results of the analysis showed that:(1)the midpoint pipe vibration amplitude induced by vehicle loads was up to 5 mm, the midpoint pipe bending moment was approximately 15 500 kN·m, and the vibration cycle was 0.25 s;(2)the higher the vehicle speed, the shorter the pipe vibration cycle time, the more intense the vibration, and the lower the effect on amplitude;and, (3)the greater the modulus of foundation soils, the smaller the amplitude of vibration and bending moment, and the lower the effect on the cycle.