挤压型大变形隧道中基于让压原理的支护理论与设计方法研究

At present, the method of taking a strong support is dominant in squeezing large-deformation tunnel. The above supporting method induced great deformation pressure while inhibiting surrounding rock deformation, easy to resulting in lots of diseases such as: lining cracking, steel twisted and bolt broken .The conventional supporting system and process face great challenges. The project Researching based on the key technical problems of squeezing large-deformation tunnel during the course of infrastructure construction in western region of our country recently years. To yielding principle as the core , With " in time - strong - yielding " supporting as the design concept, put forward the yielding supports system consisting of yielding bolt, sprayed concrete, pressure controller and steel arch, etc. Through the study of interaction mechanism of surrounding rock-supporting system , the mechanical properties of yielding artifacts, key design parameters such as: yielding point, yielding value,etc. under the condition of yielding support in squeezing large-deformation tunnel, to reveal the core technical problems of yielding supports system ,then establish supporting theory and design method of yielding supports system in squeezing large-deformation tunnel。Research is expected to open up new ground of supporting design in squeezing large-deformation tunnel。

目前，“强支硬顶”的支护手段在挤压型大变形隧道处置中占主导地位，上述支护措施在抑制围岩变形的同时诱发了极大的形变压力，导致隧道支护结构易出现诸如衬砌开裂、钢支撑扭曲、锚杆拉断等病害问题，常规支护体系及工艺受到了极大的挑战。本项目紧密结合近年来我国西部地区基础设施建设过程中大量出现的挤压型大变形隧道所面临的关键技术问题开展研究，以让压原理为核心，以 “及时-强-让压”支护为设计理念，提出基于让压锚杆+可缩型钢拱架+带让压控制器的喷射混凝土等组成的让压支护体系。通过对挤压型大变形隧道中让压条件下围岩-支护系统的相互作用机理、各让压构件的力学特性、让压支护体系中起始让压点、让压量等关键设计参数的系统研究，以期在探明让压支护系统核心技术问题的基础上，最终形成挤压型大变形隧道中让压支护体系的支护理论与设计方法。研究成果有望为挤压型大变形隧道的支护设计开辟新的蹊径。

以近年来我国西部地区基础设施建设过程中大量出现的挤压型大变形隧道为工程背景，基于提出的及时-强-让压支护理念为核心，采用资料调研、室内与现场试验、理论计算与数值分析相结合的综合研究手段，通过对让压支护作用机理、让压构件力学特性的分析，对挤压型大变形隧道中的让压锚索/杆的力学特性、让压支护体系的合理构成、让压支护体系中的关键设计参数等重要技术问题开展系统深入研究，取得了以下主要研究成果：.1）揭示了“强支护”、“分层支护”与“及时-强-让压”三种支护模式在挤压型大变形隧道中围岩-支护体系的力学演化特征及其作用机理；探明了“强支护”、“分层支护”模式下结构变形破坏的成因机制；.2）探明了让压支护体系中让压锚杆/索、可缩型拱架与让压控制器等核心支护构件的力学特性，提出了以让压锚杆/索为核心构件的让压支护系统构成；.3）基于不同挤压因子下支护力效果分析，提出了“强支护”、“让压支护”的适宜性标准； .4）提出挤压型大变形隧道中让压锚杆/索的合理锚固型式，提出了考虑岩体有无蠕变条件下让压支护体系中支护强度、起始让压点、让压量及让压荷载等关键技术参数与围岩-结构稳定性间的相互作用关系，提出了依托工程中让压支护体系的关键设计参数；.5）揭示了以让压锚杆+钢拱架+喷射混凝土等构件为主组成的让压支护体系的力学特性，通过现场试验探明了实际工程中及时-强-让压支护体系的协同变形机制，形成了让压支护体系的设计理论与方法。