地表堆载作用下盾构隧道纵向受力机制试验研究

Experimental investigation on longitudinal mechanical mechanism of shield tunnels subjected to ground surface surcharge

通过开展室内模型试验,探究地表堆载诱发下盾构隧道纵向受力变形特性。应用3D打印技术制作的盾构隧道模型,可以较好地反映真实盾构隧道管片结构特点,克服精细化盾构隧道模型制作困难的问题。首先通过开展盾构隧道模型集中荷载试验,探究盾构隧道纵向等效抗弯刚度变化规律;其次开展地表堆载试验,研究地表堆载诱发下盾构隧道受力与变形特征。试验结果表明:盾构隧道纵向等效抗弯刚度有效率并非一个常量,而是随着集中荷载增大而减小,本试验得到其值在0.176~0.044范围;在地表堆载诱发下,盾构隧道拱顶沉降呈正态分布曲线形态,主要沉降范围在加载宽度范围内;地表堆载作用下拱顶土压力分布变化特点与拱顶沉降相似;随着地表荷载增加,通过隧道中间环四周土压力监测发现,拱顶土压力增量最大,拱底次之,拱腰最小;受地表荷载作用,盾构隧道衬砌结构发生“横鸭蛋”状收敛变形,其中拱顶位移最大,拱腰次之,拱底最小。试验结果揭示了盾构隧道结构变形特性和地表堆载条件下盾构隧道与地层相互作用机制,对突发堆载下既有隧道的保护提供了参考依据。

Experimental model is conducted to explore the deformation characteristics of shield tunnels when subjected to the ground surface surcharge.In this paper,the 3D printing technology is applied to manufacture the shield tunnel model.The 3D printed shield tunnel model veritably reflects the structural features of shield tunnel linings,which overcomes the difficulty of manufacturing elaborate shield tunnel models.The concentrated load test is first carried out to investigate the characteristics of the longitudinal equivalent bending stiffness efficiency of shield tunnel.The ground surface surcharge test is then conducted to study the stress and deformation characteristics of shield tunnel induced by the ground surface surcharge.The results from the experiment test show that the longitudinal equivalent bending stiffness efficiency is not a constant,but decreases with the increase of load.Its value varies from 0.176 to 0.044 in the test.It is observed that normal distribution curve is observed in the tunnel crown when subjected to the ground surface surcharge.The main settlement range is within the width of surcharge.Moreover,the distribution characteristics of the earth pressure on the tunnel crown has a similar pattern as the settlement of the tunnel crown.With the increase of surcharge,the induced earth pressure on the tunnel crow is greatest,followed by the tunnel invert and the induced earth pressure on the tunnel waist is smallest according to the measurement around the middle ring of the tunnel.The shield tunnel lining occurs“horizontal egg”-like convergence induced by the ground surface surcharge.It is found the displacement in the tunnel crown is largest,followed by the tunnel waist and the smallest displacement is observed in the tunnel invert.The experimental tests reveal the deformation characteristics of the shield tunnel and the interaction between the shield tunnel and the surrounding soil layers.It will provide valuable references for protection of existing tunnel when subjected to the sudden ground surface surcharge.