循环爆破荷载下围岩损伤的试验研究与理论分析

发布时间：2018-06-26 04:30

本文选题：循环爆破 + 深埋隧洞　；参考：《山东建筑大学》2017年硕士论文

【摘要】：伴随着我们国家对水利水电的大力支持,西南地区的水利水电工程正在不断地展开。水电站在建设的过程中,由于很多是在高地应力下进行开挖,人工开挖比较困难,更多的要借助爆破等方式进行。在爆破的过程中,围岩在循环爆破荷载的作用下会不断发生损伤,研究围岩的损伤变化对于保证隧洞的安全性和耐久性事关重要。以及根据围岩的等级和隧洞围岩的损伤变化来设计支护结构,起到一定的参考作用。本文依据国家自然科学基金项目“循环爆破荷载作用下隧洞围岩损伤演化机理研究”,以锦屏一级水电站引水隧洞为工程背景,进行相关条件下的模型试验,来分析围岩在循环爆破荷载下的损伤情况。通过自行设计模型箱、研发相似材料,完成相关试验。主要研究内容如下:(1)模型箱的尺寸设计为了能够满足在实验过程中的方便性,以及考虑到模型的空间范围,其中本次试验的相似比取10。该引水隧洞三维模型试验系统主要包括反力架、液压系统,以及测量系统和数据采集系统这四个部分。(2)经过不断地研究和尝试,选取石英砂和铁粉作为骨料,重晶石粉作为调节剂,松香和酒精的混合溶液作为胶结剂,将这些材料混合而成。将其作为研究循环爆破荷载下围岩损伤的相似材料。(3)围压为0的时候,随着循环爆破次数的增加,在介质中的声速会发生不断降低。也就是说经过循环爆破的作用,介质的完整性在不断劣化,也就是说损伤不断加剧。(4)考虑围压的影响,5MPa、20MPa与没有围压的对比。介质的损伤度与应力场的初始水平有关,相同的爆破次数下围压越小,则损伤度越大;相反,围压越大,那么损伤度就会越小。同时,可以观察到当围压为0时,损伤度曲线比较陡,随着围压的增大,损伤度曲线会逐渐趋于平缓状态,说明围岩的损伤在围压的影响下变小,即围岩的损伤在围压下随着爆破次数的增加而减小。微差爆破能够增强岩石的破碎,但是对围岩的损伤增加不明显。每次爆破围岩在循环爆破荷载下的损伤不同,经过五次爆破之后,第三次爆破围岩损伤最大,第二、四次爆破围岩损伤次之,第一、五次爆破围岩损伤最小。(5)通过拟合曲线,声速声速变化率与爆破开挖深度曲线和损伤度与爆破开挖深度曲线变化趋势总体是相同的,声速变化率和损伤度都随着爆破开挖深度的增加而不断增大。
[Abstract]:With the great support of our country, hydropower projects in southwest China are being carried out continuously. During the construction of hydropower stations, many of them are excavated under high ground stress, so it is more difficult to excavate by hand and more by means of blasting. In the process of blasting, the damage of surrounding rock will occur continuously under the action of cyclic blasting load, so it is important to study the damage change of surrounding rock in order to ensure the safety and durability of tunnel. The supporting structure is designed according to the grade of surrounding rock and damage change of tunnel surrounding rock, which plays a certain reference role. Based on the project of National Natural Science Foundation of China, "study on damage evolution mechanism of surrounding rock under cyclic blasting load", taking the diversion tunnel of Jinping Grade I Hydropower Station as the engineering background, the model test under relevant conditions is carried out. To analyze the damage of surrounding rock under cyclic blasting load. Through self-design model box, research and development of similar materials, complete the relevant tests. The main contents are as follows: (1) in order to satisfy the convenience of the experiment and the spatial range of the model, the similarity ratio of the model box is 10. The three-dimensional model test system of the diversion tunnel mainly includes four parts: reaction frame, hydraulic system, measurement system and data acquisition system. (2) after continuous research and trial, quartz sand and iron powder are selected as aggregate. The barite powder is used as regulator, and the mixture of rosin and alcohol is used as binder to mix these materials. (3) when the confining pressure is 0, the sound velocity in the medium will decrease with the increase of cyclic blasting times. That is to say, the integrity of the medium is deteriorating through cyclic blasting, that is, the damage is increasing. (4) considering the effect of confining pressure, the effect of 20 MPA is compared with that without confining pressure. The damage degree of the medium is related to the initial level of the stress field. The smaller the confining pressure is, the greater the damage degree is under the same blasting frequency; on the contrary, the greater the confining pressure is, the smaller the damage degree will be. At the same time, it can be observed that when the confining pressure is 0, the damage degree curve is steeper. With the increase of confining pressure, the damage degree curve tends to be gentle, which indicates that the damage of surrounding rock becomes smaller under the influence of confining pressure. The damage of surrounding rock decreases with the increase of blasting times under confining pressure. Millisecond blasting can enhance rock fragmentation, but damage to surrounding rock is not obvious. The damage of surrounding rock in each blasting is different under cyclic blasting load. After five times blasting, the damage of surrounding rock in the third blasting is the biggest, the damage in the surrounding rock in the second and fourth blasting is the second, and the damage in the surrounding rock in the first and fifth blasting is the least. (5) by fitting curve, the damage of surrounding rock in the second and fourth blasting is the least. The variation trend of sound velocity change rate and blasting excavation depth curve and damage degree is the same as that of blasting excavation depth, and the sound velocity change rate and damage degree increase with the increase of blasting excavation depth.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV542;TV223

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