长大承压过水隧洞普遍存在于各大水电工程，是关乎电站安全运行与效益保障的重要水工建筑物。受过流形式与隧洞布置方式的影响，水电工程承压过水隧洞多数采用钻爆法施工技术；受隧洞埋深与开挖方式的影响，伴随隧洞开挖进程产生了不利于衬砌与防渗处置的卸荷扰动区围岩。卸荷扰动区围岩往往具有松弛变形与裂隙贯通的特征，既可能导致衬砌存在因非完全接触而产生变形破坏，也可能导致内外高渗压产生渗透潜蚀型破坏，从而严重影响施工、运行及检修期间隧洞围岩的安全性。

本文以某电站深埋引水隧洞为背景，以钻爆法施工技术产生的卸荷扰动区围岩为对象，综合采用理论分析与试验研究相结合的方式，研究开挖方式与卸荷渗流环境下，隧洞卸荷扰动区围岩的力学参数的变化规律及其变形破坏机理。主要研究结论如下：

（1）考虑隧洞开挖进程中不同区域岩体所处应力状态差异性特点，开展了常规加卸载力学试验，对比研究了加载和卸载条件下岩样的力学特征。结果表明：加载条件下，围压是决定岩样力学性质的主导因素；围压增加，岩样的峰值强度增大、弹性模量增加、泊松比减小。卸载条件下，侧向变形远大于轴向变形；围压和卸荷速率增大，岩样的峰值强度都随之增加。对比分析发现，岩样加载状态比卸荷状态下的强度更高，卸荷比加载时的变形更大、更易发生破坏；加卸载条件下宏观破坏形态均表现为一条贯穿岩样的剪切破裂面。

（2）考虑钻爆法施工的分部开挖隧洞，分部开挖方式或强度，导致开挖岩体拥有不同卸荷速率，开挖扰动致使隧洞围岩形成卸荷扰动区。进而，参考常规加卸载力学试验所得数据开展了考虑不同卸荷速率的室内力学试验。结果表明：卸荷损伤岩样制备阶段，初始围压和卸荷速率越小，卸荷损伤岩样体应变值由正转负越快，即岩样损伤越快、出现侧向扩容现象越早。此外，初始围压对强度及变形的影响大于卸荷损伤速率；卸荷损伤岩样再卸载破坏阶段，卸荷量和卸荷速率是影响岩样强度和变形的重要因素；卸荷量较大时，岩样强度较低、变形较大；卸荷速率较大时，岩样强度较大、变形较小。综合对比分析初始围压、卸荷速率及卸荷量对岩样强度及变形破坏特征的影响，其重要程度为初始围压＞卸荷量＞卸荷速率。

（3）考虑隧洞开挖致使围岩松动产生裂隙网络，渗透侵蚀加剧裂隙衍生、结构劣化，开展了卸荷损伤岩样再加卸载渗流试验，分析了不同孔压对卸荷损伤岩样力学性质及变化规律的影响。结果表明：不同卸荷量损伤岩样在孔压为1MPa承压浸泡阶段，其体应变和侧胀系数随着承压时间的增长而增加，变形模量减小；孔压为1.5MPa时，卸荷量为70%时卸荷损伤岩样在承压浸泡阶段发生侧向扩容破坏。再加卸载渗流过程中，卸荷损伤岩样的渗透率随着初始围压的增大而减小，随着卸荷量和水压的增大而增加。综合对比发现，影响岩样强度、变形、渗透率特征的因素中，其重要程度为初始围压＞卸荷量＞水压。

Long pressure tunnel is widely used in major hydropower projects, and it is an important hydraulic structure for safe operation and benefit guarantee of power station. Due to the influence of flow form and tunnel layout, most of the confined water tunnel construction technology is drilling and blasting method. Affected by the depth and excavation method of the tunnel, surrounding rock in the disturbed area of unloading is produced along with the excavation process of the tunnel, which is not conducive to lining and anti-seepage disposal. The surrounding rock in the unloaded disturbed area is usually characterized by loose deformation and fracture connection, which may lead to deformation and failure of the lining due to incomplete contact or infiltration and potential erosion caused by high internal and external osmotic pressure, thus seriously affecting the safety of the surrounding rock during construction, operation and maintenance.

Based on a power embedded diversion tunnel as the background, drilling and blasting method construction technology by unloading disturbance zone of surrounding rock, combining theoretical analysis and experimental study on the way of combining research environment, excavation and unloading seepage, the law of mechanical parameters of surrounding rock deformation and failure mechanism of unloaded disturbance zone of tunnel was studied. The main conclusions are as follows:

(1) Considering the difference of stress state of rock mass in different areas during tunnel excavation, conventional loading and unloading mechanical tests were carried out to compare the mechanical characteristics of rock samples under loading and unloading conditions. The results show that the confining pressure is the dominant factor to determine the mechanical properties of rock samples under loading; With the increase of confining pressure, the peak strength, elastic modulus and Poisson's ratio of rock samples increase. Under the unloading condition, the lateral deformation is much larger than the axial deformation; With the increase of confining pressure and unloading rate, the peak strength of rock samples increases. It is found that the strength of rock samples under loading is higher than that under unloading, and the deformation of rock samples under unloading is larger and more prone to damage than that under loading; Under the loading and unloading conditions, the macroscopic failure mode is a shear fracture surface penetrating the rock sample.

(2) Considering the partial excavation of tunnel by drilling and blasting method, the excavation method or intensity of partial excavation leads to different unloading rates of excavated rock mass, and the excavation disturbance leads to the formation of unloading disturbance area of tunnel surrounding rock. Furthermore, referring to the data of conventional loading and unloading mechanical tests, indoor mechanical tests considering different unloading rates were carried out. The results show that the smaller the initial confining pressure and unloading rate, the faster the volume strain of the unloaded damaged rock sample changes from positive to negative, that is, the faster the damage of the rock sample and the earlier the lateral dilatancy phenomenon occurs. In addition, the effect of initial confining pressure on strength and deformation is greater than that of unloading damage rate; In the unloading failure stage of unloading damaged rock samples, the unloading amount and unloading rate are important factors affecting the strength and deformation of rock samples; When the unloading amount is large, the rock sample has low strength and large deformation; When the unloading rate is large, the strength of the rock sample is large and the deformation is small. The effects of initial confining pressure, unloading rate and unloading amount on the strength and deformation failure characteristics of rock samples are comprehensively compared and analyzed. The importance degree is initial confining pressure > unloading amount > unloading rate.

(3) Considering that the tunnel excavation causes the loosening of surrounding rock to produce fracture network, and the seepage erosion intensifies the fracture derivation and structural deterioration, the unloading and loading seepage test of unloading damaged rock samples is carried out, and the effects of different pore pressure on the mechanical properties and change rules of unloading damaged rock samples are analyzed. The results show that when the pore pressure of the damaged rock samples with different unloading amounts is 1MPa, the volume strain and lateral expansion coefficient increase with the increase of bearing time, and the deformation modulus decreases; When the pore pressure is 1.5MPa and the unloading amount is 70%, the unloading damaged rock sample has lateral dilatancy failure during the pressure immersion stage. In the process of loading and unloading seepage, the permeability of unloading damaged rock sample decreases with the increase of initial confining pressure, and increases with the increase of unloading volume and water pressure. Through comprehensive comparison, it is found that the importance of the factors affecting the strength, deformation and permeability of rock samples is initial confining pressure > unloading capacity > water pressure.

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