特大圆形锚碇沉井下沉系数和稳定系数研究

Study of Sinking Factor and Stability Factor for Large Round Caissons Used for Anchor Block Foundation

为了解特大圆形锚碇沉井下沉施工中下沉系数和稳定系数变化规律,以武汉鹦鹉洲长江大桥北锚碇高43m、外径66m的沉井基础为背景,运用太沙基理论对3次接高与3次下沉的不排水沉井施工方案各工况进行稳定性验算。结果表明:在前2次沉井下沉过程中,其下沉系数较大,下沉较容易;第3次下沉过程中,其下沉系数减小,下沉较困难,须采取相应助沉措施。沉井的正面阻力和侧摩阻力在各下沉工况下均随着沉井的下沉深度呈线性增加,且正面阻力在沉井节段接高稳定工况下增幅达到最大,在刃脚踏面支承工况下增幅最小,稳定性均满足要求。

To study the variation law of the sinking factor and stability factor in the sinking construction of large round caissons,the caisson foundation,measuring 43 mhigh and 66 min outer diameter,of Yingwuzhou Changjiang River Bridge in Wuhan was taken as the study background.The Terzaghi theory was used to carry out stability check of the load cases in the undrained construction of the caisson which experiences three times of height-elongation and three times of sinking.The results of the check show that in the first two times of the caisson sinking processes,the sinking factor is great and the sinking of the caisson is much easier.Whereas in the third time of sinking,the sinking factor decreases,such that the sinking is a little difficult,and the sinking-aid measures should be taken.The front resistance and lateral friction resistance of the caisson in each sinking load case exhibits linear increase as the increase of the sinking depth of the caisson.The increment of the front resistance reaches the maximum under the stable load case of the caisson elongation,while being minimum under the condition of being supported by the tread surface of the cutting edge,and the stability suits the requirements.