冰雪灾害条件下南方地区岩锚失效的机理研究

Stress in anchor supporting structure and slope will be changed with extreme snow disasters, deterioration of mechanical properties of anchor supporting structure will occur with freeze-thaw cycles,even it can lead to landslide and collapse of slope and great damage to people's life and wealth. This project will study on the mechanism of mechanical properties of anchor supporting structure under extreme ice and snow disasters with laboratory model experiments, theoretical analysis and numerical simulation.In model experiments, stress in anchor, stress in cementation plane between anchor and anchor agent, stress in cementation plane between anchor agent and rock will be measured during freeze-thaw cycles. Anchor force and prestress loss in prestressed anchor also will be measured .The deterioration of bonding properties will be researched and a mathematical model of bond degradation will be given. The durability of grouted rock anchor with freeze-thaw cycles will be researched. The numerical model with temperature field and stress field will be built to analysis the stability of slope based on laboratory experiments. It will provide theoretical guidance for construct and design anchor supporting structure on rock slope in south China, and provide academic basis for the standards of prevention of geological disasters under the extreme ice and snow disasters,and also provide reference for the supplement of the standards of prevention of geological in frozen soil region.

在极端冰雪灾害条件下，冻融循环使锚固支护结构和边坡内部应力的平衡状态发生改变，支护结构力学性能劣化甚至失效，导致产生新的滑坡与崩塌，造成人民生命财产的重大损失。本项目拟综合运用模型实验、理论分析和数值模拟相结合的方法，对冰雪灾害气候下我国南方地区岩锚失效的机理进行研究。通过模型试验测定冻融循环过程中锚杆、砂浆-锚杆粘结面以及砂浆-围岩粘结面的应力变化情况；测定冻融循环前后锚杆锚固力的变化及预应力锚杆的预应力损失情况；研究冻融循环作用下岩锚粘结性能的退化机理，给出粘结退化的数学模型；分析冻融循环对锚杆支护结构耐久性的影响；建立温度场耦合应力场的锚杆支护结构的数值模型，研究冻融循环作用下锚固岩质边坡的稳定性。所得结论将为今后南方地区锚固支护结构的设计和施工提供理论依据，也为极端冰雪灾害条件下地质灾害防治标准及相关规范的建立提供参考，并为冻土区地质灾害防治标准及相关规范的补充和完善提供参考。

针对极端冰雪条件下温度变化引起砂浆岩石锚杆力学性能劣化的现象，研究冻融循环对其锚固能力的影响。利用室内模型试验得到不同冻融循环周期下锚杆位移和锚固力的大小，以及锚杆应力、围岩应力、锚杆和砂浆胶结面剪应力的变化，从锚杆荷载传递机理出发，研究冻融循环作用下锚杆的破坏模式和影响锚杆锚固性能的主要原因。主要结论如下：（1）锚杆的应变变化滞后于温度变化，应变曲线相位滞后于温度曲线相位约π/4。随着冻融次数的增加，锚杆的应变增长量变大，水泥砂浆和围岩胶结面产生了部分不能恢复的塑性变形，冻融损伤劣化加剧。经过冻融循环的锚杆破坏时极限荷载降低，变形增大。（2）冻融循环加速了荷载向被加固体内部的传递，减少了浅层岩体裂隙的发育，对风化层浅的坡体来说有一定的积极意义，但是从另一个角度来看，需要增加锚杆的安全储备，增强深层锚杆的锚固能力。(3)常温下孔口砂浆发生剪切破坏，而遭受冻融循环的孔口砂浆发生倒锥形拉破坏，锚杆产生突增的变形，荷载—位移曲线出现明显的拐点。随着冻融周期的增加，荷载—位移曲线拐点出现提前，锚杆极限荷载降低，变形增大。（4）在冻融循环的过程中，锚杆的预应力逐渐损失，预应力锚杆的最终变形超过全长粘结锚杆。与非预应力试件相比，预应力加速了水泥砂浆粘结面的破坏，加速荷载向锚杆深处的传递。（5）注浆岩石锚杆使用螺纹钢时，锚杆和砂浆的破坏面上既有砂浆与锚杆的粘结破坏，又有砂浆的剪切破坏，并且产生局部滑移后的摩阻力对锚杆的极限承载力也有很大贡献。根据试验结果得到了适用于此次试验条件下的平均剪切强度和极限承载力随冻融循环周期变化的退化公式。