当前软岩隧道初期支护因沉降变形量大而造成的成本消耗高问题较突出，初期支护底脚作用力与锁脚锚杆抗力不平衡是隧道初期支护沉降的主要原因，其中建立支护底脚与锁脚锚杆之间力的平衡关系是控制隧道初期支护沉降变形的重要前提。以弹性地基梁柱原理和摩擦桩原理来计算分析锁脚锚杆的内力和位移及其与地基的反力关系，以此确定锁脚锚杆的承载能力；通过分析锁脚锚杆对支护结构的柔度，确定其与支护结构的相互影响，进而建立考虑锁脚锚杆对支护结构底脚影响的支护结构力学计算模型，计算其作用于锁脚锚杆端上的作用力作为锁脚锚杆的设计依据；按照上述原理，分析了Ⅴ级围岩当前流行的42锁脚锚管的不足，并示例计算分析了108锁脚锚管的承载能力；最后以Ⅵ级围岩风积砂隧道施工的实例来说明“分布式”加强锁脚锚管以及锁脚锚桩控制支护沉降变形的显著效果验证技术的可行性；结论认为软岩隧道初期支护可按照“荷载—结构”原理确定围岩与支护、支护与锁脚锚杆之间的作用力与反作用力关系，达成支护结构之间力的平衡稳定以实现控制支护沉降的目的。
Presently, the
cost consumption caused by large settlement deformation of primary support of
soft rock tunnel is high. The imbalance between the force of primary support
foot and the resistance of locking bolt is the main reason causes the
settlement of primary support of tunnel. Hence, the force balance between
primary support foot and locking bolt is an important premise to control the
settlement deformation of primary support of tunnel. In this paper, based on
the elastic foundation beam column principle and the friction pile principle,
the internal force and displacement of the locking bolt and its reaction
relationship with the foundation are calculated and analyzed, so as to
determine the bearing capacity of the locking bolt. Then, by analyzing the
flexibility of the locking bolt to the supporting structure, the interaction
between the locking bolt and the supporting structure is determined, the
mechanical calculation model of the supporting structure considering the
influence of the locking bolt on the bottom foot of the supporting structure is
established further, and the force acting on the end of the locking bolt is
calculated as the design basis of the locking bolt. On this basis, the current
popular problems of grade Ⅴ surrounding rock using 40 foot locking bolt are analyzed, and the bearing capacity of 108 foot locking bolt is analyzed through example calculation.
Finally, taking the construction of grade Ⅵ surrounding
rock aeolian sand tunnel as an example, the remarkable effect of distributed
strengthened foot locking anchor pipe and pile on controlling support
settlement and deformation is validated. It is concluded that the reaction
between surrounding rock and support and that between support and foot locking
bolt can be determined according to the principle of loadstructure method, so as to achieve the balance and stability of the
force between support structures and further control the support settlement.
