近年来随着我国大水网的建设，大量水利工程稳步推进。引水隧洞作为不可或缺的一部分，其围岩的稳定性对于安全运营至关重要。在隧洞工程建设的过程中，因为开挖扰动等因素，打破了地下水原有的渗流路径，在隧洞上方形成天然的渗流漏斗。开挖也使得原本处在相对平衡状态下的岩体发生应力重分布而产生一定范围的松动圈，导致围岩出现大量裂隙，为地下水提供了渗流通道。在渗透压力的驱使下，地下水在孔隙、裂隙中持续渗流，不断冲刷裂隙侧壁，携带裂隙表面游离颗粒流失。并且水对于岩石颗粒间胶结物质具有软化润滑作用，同时也会将易溶矿物分解，造成岩石颗粒间粘结作用降低，导致围岩物理力学性质劣化，工程性质变差。随着地下水长期渗透，劣化作用不断加剧，影响深度越来越大，威胁隧洞长期安全稳定。

针对此问题，本文以新疆某隧洞工程凝灰岩为研究对象，以探究该工程凝灰岩在持续渗透作用下物理力学特性的演化规律为研究内容，以论证凝灰岩隧洞裸岩洞段长期稳定性为研究目标开展相关研究工作。针对该隧洞工程场区环境，设计并开展了渗透试验和渗透后试件的单轴、三轴压缩试验以及微细观测试，探究了凝灰岩在渗透作用下物理力学特性的劣化程度，揭示了凝灰岩矿物成分、细观结构和物理力学特性在渗透作用下的变化规律。结合室内试验结果，基于达西定律建立了岩体力学参数与渗透预测年限之间的关系，并采用Hoek-Brown准则，计算得到不同渗透预测年限后的岩体物理力学参数，并结合数值模拟，论证了凝灰岩裸岩洞段长期稳定性。论文主要研究内容及成果如下：

（1）开展了渗透试验以及渗透后试件的单轴和三轴压缩试验，测定了1、2、3MPa渗透压力下持续作用10、20、30、40、50天下的单轴、三轴抗压强度，绘制了试件应力应变曲线，通过Mohr-Coulomb准则计算得到了不同渗透压力持续不同天数下试件的抗剪强度参数（粘聚力和内摩擦角），建立了试件单轴、三轴抗压强度、弹性模量、粘聚力和内摩擦角与渗透天数的关系，分析了渗透作用的劣化效应。结果显示：①试件的物理力学参数均随渗透天数的增加呈降低趋势，在持续渗透0~20天内各参数降低程度较明显，随着渗透天数的增加，其作用逐渐减弱。②单轴压缩破坏后，以劈裂破坏为主，三轴压缩在有围压侧向约束条件下呈现出张剪复合型破坏特征。随着渗透天数增加局部细微裂纹逐渐增多，渗透压力越大处，试件受渗透作用越明显。③渗透作用下不断冲刷孔隙、裂隙侧壁，水对于试件骨架颗粒之间联结的弱化以及软化润滑作用，使得试件内部孔隙、裂隙的发育扩展，导致抗压强度、弹性模量、粘聚力和内摩擦角与纵波波速协同降低。

（2）对渗透试验后的试件开展了微细观测试，研究了不同渗透天数下，试件的矿物成分和内部孔隙结构损伤演化规律。结果显示：①渗透天数在0~10天内，试样矿物成分发生改变，在渗透作用下试件内部矿物成分伊利石和高岭石逐渐被溶蚀。②随着渗透天数的增加，试样表面越来越粗糙，在渗透时间40~50天阶段，试件内部不仅在渗透作用下继续产生新的孔隙、裂隙，而且相互发育，搭接形成贯穿裂纹。③渗透作用持续50天后渗透作用使得试件内部细小孔隙发育扩展，渗透持续作用越长，会使得细小孔隙逐渐连通，试件内部出现孔径相对较大的孔隙，孔隙结构变得复杂。

（3）结合室内试验研究成果，基于达西定律建立了岩体力学参数与渗透预测年限之间的关系，并采用Hoek-Brown准则，计算得到不同渗透年限后的岩体力学参数，利用数值模拟对比分析了不同渗透年限下隧洞位移、塑性区分布以及围岩最小稳定性系数。结果显示：①持续渗透作用下围岩位移分布规律大致相同，隧洞竖向和水平位移随渗透年限的增加逐渐增大，围岩最小稳定性系数逐渐减小。②隧洞围岩变形量、塑性区均小于规范沉降控制标准，围岩最小稳定性系数均大于1，隧洞基本处于稳定状态。③凝灰岩裸岩洞段在长期内水冲刷与外水渗透作用下，局部有潜在破坏的可能性，建议在外水压力相对较高的洞段喷射混凝土进行局部加固，一定程度可减小渗透作用对围岩的侵蚀作用，进而防止因岩体内部裂隙发育扩展，而造成部分岩体物理力学特性劣化。

In recent years, with the construction of China's large water network, the majority of water conservancy projects have been steadily advanced. As an integral part of diversion tunnels, the stability of the surrounding rock is critical to safe operation. In the process of tunnel construction, due to excavation disturbance and other factors, the original seepage path of groundwater was broken, and a natural seepage funnel was formed above the tunnel. Excavation also causes stress redistribution of the rock mass in a relatively equilibrium state to produce a certain range of loosening circles, resulting in the majority of fractures in the surrounding rock, providing a seepage channel for groundwater. Driven by osmotic pressure, groundwater continues to seep in the pore fractures, continuously scouring the side walls of the fractures, and carrying the loss of free particles on the surface of the fractures. Moreover, water has a softening and lubricating effect on rock particles, and at the same time, it will decompose soluble minerals, resulting in reduced bonding between rock particles, resulting in deterioration of the physical and mechanical properties of surrounding rock and deterioration of engineering properties. With the long-term infiltration of groundwater, the deterioration effect is intensifying, and the depth of impact is increasing, threatening the long-term safety and stability of the tunnel.

In view of this problem, this paper takes the tuff of a tunnel engineering in Xinjiang as the research object, explores the evolution of the physical and mechanical properties of the tuff under continuous infiltration of the project, and carries out relevant research work with the long-term stability of the bare rock section of the tuff tunnel as the research goal. According to the environment of the tunnel engineering site, the permeation test and the uniaxial and triaxial compression test and microscopic test of the infiltrated specimens were designed and carried out, which explored the deterioration of the physical and mechanical properties of tuff under infiltration, and revealed the change law of mineral composition, mesostructure and physical and mechanical properties of tuff under infiltration. Combined with the results of indoor experiments, the relationship between the mechanical parameters of rock mass and the permeability age is established based on Darcy's law, and the physical and mechanical parameters of rock mass after different permeation years are calculated by using the Hoek-Brown criterion, and the long-term stability of tuff bare rock cavern section is demonstrated by numerical simulation. The main research contents and achievements of the paper are as follows:

(1) The permeation test and the uniaxial and triaxial compression tests of the permeated specimens were carried out, the uniaxial and triaxial compressive strength under 10, 20, 30, 40 and 50 days under the permeation pressure of 1, 2 and 3MPa were determined, the stress-strain curve of the specimen was drawn, the shear strength parameter cohesion and internal friction angle of the specimen under different days of permeation pressure were calculated by the Mohr-Coulomb criterion, and the uniaxial and triaxial compressive strength, elastic modulus of the specimen were established. Cohesion and internal friction angle in relation to days of penetration. The results showed that: ①The physical and mechanical parameters of the specimens decreased with the increase of the number of permeation days. The degree of reduction of each parameter was obvious within 0-20 days of continuous infiltration, and its effect gradually weakened with the increase of infiltration days. ②After the failure of uniaxial compression, the splitting failure is the mainstay, and the three-axis compression presents the characteristics of tensile-shear composite failure under the condition of confining pressure lateral constraint. With the increase of the number of permeation days, the local fine cracks gradually increase, and the greater the permeation pressure, the more obvious the permeation effect of the specimen. ③Under the action of osmosis, the side wall of the pore fracture is continuously washed, and the weakening and softening lubrication effect of water on the connection between the skeleton particles of the specimen makes the development and expansion of the internal pore fracture of the specimen, resulting in the synergistic decrease of compressive strength, elastic modulus, cohesion and internal friction angle and longitudinal wave velocity.

(2) Microscopic tests were carried out on the specimens after the penetration test, and the evolution of mineral composition and internal pore structure damage of the specimens under different penetration days was studied. The results showed that: ①Within 0~10 days, the mineral composition of the sample changed, and the mineral components of illite and kaolinite inside the specimen were gradually dissolved under the action of infiltration. ②With the increase of penetration time, the surface of the specimen becomes more and more rough, in the stage of 40 ~ 50 days of penetration time, the inside of the specimen not only continues to produce new pores and cracks under the action of infiltration, but also develops each other, lapping to form through cracks. ③After the osmotic effect lasts for 50 days, the infiltration makes the development and expansion of the fine pores inside the specimen, and the longer the permeation lasts, the fine pores will gradually connect, and the pores with relatively large pore sizes appear inside the specimen, and the pore structure becomes complex.

(3) Combined with the results of indoor experiments, the relationship between the mechanical parameters of rock mass and the prediction period of permeability was established based on Darcy's law, and the mechanical parameters of rock mass after different permeability years were calculated by using Hoek-Brown criterion, and the tunnel displacement, plastic zone distribution and minimum stability coefficient of rock mass under different permeation years were compared and analyzed by numerical simulation. The results show that: ①The displacement distribution of rock mass under continuous permeation is roughly the same, the vertical and horizontal displacements of the tunnel gradually increase with the increase of permeation age, and the minimum stability coefficient of rock mass gradually decreases. ②The deformation amount and plastic zone of the rock mass of the tunnel are less than the standard settlement control standard, the minimum stability coefficient of the rock mass is greater than 1, and the tunnel is basically in a stable state. ③Under the long-term internal water erosion and external water infiltration of the tuff bare rock cave section, there is a possibility of local potential damage, it is recommended to carry out local reinforcement of the injection concrete in the hole section with relatively high external water pressure, which can reduce the erosion effect of osmotic on the rock mass to a certain extent, and then prevent the deterioration of the physical and mechanical properties of part of the rock mass due to the development and expansion of internal fractures in the rock mass.

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