盾构隧道穿越软塑红粘土覆盖型岩溶区的处理方法

Countermeasures for the Shield Tunnel Passing through the Karst Area Overlying Soft Plastic Red Clays

文章分析了岩溶上覆地层塌陷机理以及软塑红粘土层及硬塑红粘土层中盾构隧道的施工风险,并制定了相应的处理措施。结果表明:隧道位于软塑红粘土层时,降水破坏了土-裂隙水-溶洞之间的平衡状态,导致红粘土流入溶洞,隧道会随着软塑红粘土的下沉而下沉;当隧道位于硬塑红粘土层中时,下面的软塑红粘土流入溶洞后,由于可塑红粘土的抗剪强度和粘聚力均较低,软塑土层塌陷,会在可塑土层和硬塑土层之间形成土洞,最终也会导致隧道下沉;当灰岩岩面倾斜度较大时,会扩大红粘土的沉降范围。通过填充高风险范围内的溶洞、对软塑红粘土层进行加固以及在岩面倾斜过大的地方增设抗滑桩等措施可防范上述工程风险。

As for the karst area overlying soft plastic red clays,artificial dewatering and construction disturbance will cause collapse of karst ground and endanger tunnel construction and operation safety.The collapsing mechanism of the soft plastic red clay overlying karst area and the construction risks of shield tunnel in soft plastic red clay and the hard plastic red clay soil layer are analyzed,and the corresponding measures are established.The results show that dewatering destroys the equilibrium state among soil,fissure water and karst cave,leads to flowing of red clay into karst cave and the tunnel will subside with the subsidence of soft plastic red clay if the tunnel is located in soft plastic red clay stratum;after flowing of soft plastic red clay into karst cave,the soft plastic red clay layer collapses and a soil cave is formed between the plastic red clay layer and the hard plastic red clay layer and eventually the tunnel subsides due to low shear strength and cohesion,if the tunnel is located in hard plastic red clay layer;if the inclination of limestone surface is large and this will extend the settlement range of red clay.The following measures like filling of karst cave within the scope of high risks,reinforcement of the soft plastic red clay layer and adding of anti-sliding piles at the place with large inclination are adopted to manage the above mentioned risks.