【作者】 田野；

【导师】 李树忱；

【作者基本信息】 山东大学 ， 土木水利（专业学位）， 2023， 硕士

【摘要】 钻爆法开挖完毕后,需要施作临时喷射混凝土封闭围岩,然后进行初期支护(喷射混凝土和钢拱架)施工。但是,受施工条件限制和施工进度影响,工程现场往往缺少临时喷射混凝土施工工序,并且初期支护不能及时跟进,导致裸岩面得不到及时封闭保护,碎裂围岩容易引起隧道出现挤压掉块、失稳破坏等工程问题,影响工程进度和工程结构的安全性、增加生产成本,严重危及施工安全并带来巨大的经济损失,是矿山法暗挖施工亟待解决的主要难题之一。薄喷支护(Thin Spray-on Liner)又称TSL,是基于新奥法原理的新型支护型式,具有施作厚度小(典型的施工厚度2～10mm左右),灵活度高等优点,薄喷支护可以快速封闭保护围岩,渗入围岩裂隙,充分发挥围岩的自承能力,克服了传统临时喷射混凝土回弹大、强度低、脆性大等缺点。然而薄喷支护在隧道支护中应用较少,其支护机理研究也存在不足。本文综合运用室内试验、理论分析、数值模拟、现场应用等方法,研究了薄喷支护的力学性能,分析薄喷支护在围岩支护中作用和承载机制,主要成果如下:(1)通过室内试验测试了薄喷材料的拉伸强度、粘结强度和压缩强度等力学特性。发现自主研发的薄喷材料能快速建立强度,在围岩变形的初期发挥力学作用,薄喷材料的断裂伸长率最大可达到65%,能够适应围岩大变形的情况;薄喷材料与岩石的界面粘结强度测试中,破坏均发生在薄喷材料的基体处,说明薄喷材料的粘结性能良好;并且测试了薄喷材料的压缩强度,为后续的数值模拟所需要的参数提供试验依据。(2)通过室内试验分析了薄喷支护对表面岩石的力学作用。通过室内试验发现,薄喷材料喷涂至岩石表面后,能够渗入碎裂岩体的缝隙中,有效限制块体间的相对运动;薄喷材料喷涂至岩石表面后与岩体形成脆-韧结构,可以提高岩体的拉伸强度,并且提高了岩石单位面积破坏所需要的能量。(3)通过线性块体承载力试验,发现喷层承载不同块体时会发生不同的破坏模式,分析得到了不同养护时间下喷层对不同块体的承载力值,并通过静力学分析求得了喷层在不同养护时间下所能承载岩石块体的最大质量,通过计算发现喷层能够有效承载拱顶脱落的小岩石块体。(4)通过数值模拟的方式,以青岛某地铁隧道为工程背景,进行工程尺度的开挖支护模拟,比较分析了 TSL支护的作用机理、喷层厚度以及支护时机的对支护效果的影响。结果表明薄喷层对控制围岩变形有一定的作用,主要功能是兜住掉落的岩石块体,保障了隧道的安全,在“锚杆+TSL”的支护体系中,锚杆能发挥控制围岩变形,保持岩体完整性的作用,TSL发挥的是防止小块体掉落的护表作用,二者协同作用,共同维持围岩的稳定。更多还原

【Abstract】 After drilling and blasting excavation,temporary shotcrete shall be used to seal the surrounding rock,and then initial support(shotcrete and steel arch)shall be constructed.However,due to the limitation of construction conditions and the impact of construction progress,the construction process of temporary shotcrete is often lacking at the project site,and the initial support can not be followed up in time,resulting in the lack of timely closure and protection of the exposed rock surface,and the fragmentation of surrounding rock is easy to cause engineering problems such as crushing,instability and damage of the tunnel,affecting the project progress and the safety of the project structure,and increasing production costs,It seriously endangers the construction safety and brings huge economic losses,which is the main problem to be solved urgently in the construction of underground excavation by mining method.Thin spray on liner is a new type of support based on the principle of NATM.It has the advantages of small construction thickness(typical construction thickness is about 2～10mm)and high flexibility.Thin shotcrete material can quickly seal and protect surrounding rock,penetrate into the cracks of surrounding rock,give full play to the self-supporting capacity of surrounding rock,and overcome the shortcomings of traditional temporary shotcrete,such as large rebound,low strength,and large brittleness.However,thin shotcrete materials are rarely used in tunnel support,and the research on its support mechanism is also insufficient.In this paper,the mechanical properties of thin shotcrete materials are studied,and the role and mechanism of thin shotcrete materials in surrounding rock support are analyzed by means of laboratory tests,theoretical analysis,numerical simulation,and field application.The main results are as follows:The tensile strength,adhesive strength and compressive strength of the thin-sprayed material were tested through laboratory tests.It is found that the self-developed thin shotcrete material can quickly establish strength and play a mechanical role in the initial stage of surrounding rock deformation.The maximum elongation at break of the thin shotcrete material can reach 65%,which can adapt to the large deformation of surrounding rock;In the test of the interface bond strength between the thin shotcrete material and the rock,the failure occurred at the base of the thin shotcrete material,indicating that the thin shotcrete material has a good bond property;The compressive strength of the thin-sprayed material was tested to provide experimental basis for the parameters required for the subsequent numerical simulation.The mechanical action of the thin shotcrete material on the surface rock mass is analyzed through laboratory tests.Through the indoor test,it is found that the thin spray material can penetrate into the cracks of the cataclastic rock mass after being sprayed on the rock surface,effectively limiting the relative movement between the blocks;The thin sprayed material forms a brittle-ductile structure with the rock mass after being sprayed onto the rock surface,which can improve the tensile strength of the rock mass and increase the energy required for unit area damage of the rock.Through the linear block bearing capacity test,it is found that different failure modes will occur when the shotcrete layer bears different blocks.The bearing capacity values of the shotcrete layer for different blocks under different curing times are analyzed and obtained.The maximum mass of the rock blocks that the shotcrete layer can bear under different curing times is obtained through static analysis.Through calculation,it is found that the shotcrete layer can effectively bear the small rock blocks falling off the arch crown.Through numerical simulation,taking a subway tunnel in Qingdao as an engineering background,an excavation and support simulation was carried out on an engineering scale.The effect of the "bolt+TSL" support mechanism,spray layer thickness,and support timing on the support effect was compared and analyzed.The results show that the thin shotcrete layer has limited ability to control the deformation of surrounding rock,but it can hold down falling rock blocks,ensuring the safety of the tunnel.TSL cannot be used as a separate bearing structure.In the "bolt+TSL" support system,the anchor rod can play a role in controlling the deformation of surrounding rock and maintaining the integrity of the rock mass.TSL plays a surface protection role in preventing small blocks from falling,and the two work together to maintain the stability of the surrounding rock.更多还原