【作者】 张磊；

【导师】 朱维申；

【作者基本信息】 山东大学 ， 岩土工程， 2009， 硕士

【摘要】 锚杆支护技术是一种非常有效和经济的岩土结构加固方法,广泛地运用于几乎所有的土木工程建设中。随着社会经济的发展,更多的岩土结构工程将会被修建,作为工程建设中重要支护措施之一的锚杆加固技术将有着长远的发展前景。在岩体工程中,由于岩体中含有大量的天然裂隙,锚杆加固技术对岩体工程的支护效果尤为明显。尽管如此,锚杆的加固机理至今尚未被研究清楚,为了更加有效地使用锚杆以保障岩体工程的施工安全性和长期稳定性,有必要就锚杆对裂隙岩体的加固效应进行进一步的研究。本研究主要从室内试验和数值模拟两方面来研究锚杆加固对裂隙岩体的力学性能的影响,通过综合分析研究结果得出一些有益于实际锚杆设计、施工的结论。在室内试验阶段,主要对三类试件进行研究,分别是完好试件、裂隙试件、加锚裂隙试件。它们的关系是:裂隙试件是在完好试件内部预置一个张开型裂隙,而加锚裂隙是在裂隙试件的内部设有锚杆,加锚裂隙试件中锚杆的锚固角有30°、45°、70°、85°四种,锚杆的个数分别有单根、双根、三根三种,不同锚固角和锚杆个数的组合形成了各种不同的加锚裂隙试件。室内试验研究的主要工作包括以下几个内容:首先,为研制出一种与实际岩体物理力学参数满足一定相似比关系的砂浆材料,设计了五组砂浆材料的配合比,并对各种配合比的砂浆完好试件进行单向压缩和劈裂试验研究,最终确定出满足相似比要求的砂浆配合比,依此相似比关系选择出一种合金铝棒作为室内试验的相似锚杆。其次,对裂隙试件、加锚裂隙试件进行单向压缩和劈裂试验研究,结合第一阶段的试验结果,分别研究单向压缩和劈裂条件下预置裂隙对砂浆材料的弱化效应以及锚杆对裂隙试件的加固效应,并获得加锚裂隙试件的单轴抗压强度及在劈裂条件下峰值荷载随锚固角度及锚杆个数增加而变化的规律。最后,对完好试件、裂隙试件、加锚裂隙试件进行双向压缩试验研究。研究了在不同侧压条件下预置裂隙对砂浆材料的弱化效应以及锚杆对裂隙试件的加固效应,并获得在双向压缩条件下加锚裂隙试件的抗压强度随锚固角度及锚杆个数增加而变化的规律以及各种试件的双向抗压强度随侧压增加而变化的规律。通过包括单向压缩、劈裂和双向压缩的综合室内试验研究,获得了锚杆个数及锚固角度对裂隙试件力学强度的影响规律;此外,通过比较各种试验条件下试件的破坏形态,研究不同试验条件下锚杆的失效模式以及锚杆对试件破坏发展过程的影响。在数值模拟阶段,使用FLAC-3D软件对完好试件、裂隙试件、加锚裂隙试件的单向压缩试验进行数值模拟,获得的各种试件的数值应力-应变曲线、砂浆材料的最大、最小主应力云图、加锚试件中锚杆的受力状态。在对加锚裂隙试件进行数值模拟时,采用FLAC-3D自带的桩结构单元来建立锚杆单元,分别采用实体单元模拟法与实体-等效法来模拟锚杆对裂隙试件的加固效果,数值模拟结果表明,实体-等效法模拟锚杆加固效果的计算结果与室内试验结果较为接近;以单锚裂隙试件的单轴压缩数值试验为例,得出了锚固角对裂隙试件力学性能的影响规律。结合室内试验与数值分析的研究结果,得出了锚杆个数及锚固角度对裂隙试件加固效应的影响规律,由于本研究中砂浆材料与锚杆材料的物理力学参数与实际岩体及锚杆严格满足相似比关系,故所得研究结果对实际工程活动具有较大的指导意义。更多还原

【Abstract】 Rock bolting represents one of the most effective and economical geo-structural reinforcing technologies widely used in practical civil engineerings. It has great prospects as more civil constructions are to be built during the socio-economic development. In the field of rock mass engineering, the reinforcing effect of the rock bolt(s) on rock mass is much more obvious due to the large number of natural fractures in rock masses. However, the mechanism of anchorage is still not being studied clearly now. The effective use of the rock bolt(s) for constructing safety and long-term stability of the rock mass engineering requires further the research into rock bolts’ anchorage effect upon rock mass.The research program studies the rock bolts’ anchorage effects on fractured specimens’ mechanical properties from the two perspectives: laboratory experiment and numerical simulation. With a comprehensive analysis of the research results, some useful directions are deduced for the design and installation of the practical rock bolt(s).In the laboratory experiment stage, the research objects are three kinds of specimens, namely intact specimens, fractured specimens and anchored-fractured specimens. Their relationship is as follows:Compared with intact specimen, fractured specimen is a specimen with an opening mode fracture, and anchored-fractured specimen is a specimen with fracture and rock bolt(s). Anchored-fractured specimen has 4 anchorage angles, which are 30 degrees, 45 degrees, 70 degrees and 85 degrees, and the numbers of rock bolts are single, binary and ternary. These 4 kinds of anchorage angles and 3 kinds of rock-bolt numbers constitute different anchored-fractured specimens.The main contents of the laboratory experiment are as follows:Firstly, design 5 groups of the mortar’s mixing proportion; test these 5 different mixing-proportion specimens’ uniaxial compressive strengths and splitting tensile strengths; define a mixing proportion that make the mortar specimen’s physical and mechanical parameters accord with a fixed similar ratio compared to the real rock mass; choose aluminium alloy bar as the similar rock bolt based on the similar ratio.Secondly, test fractured and anchored-fractured specimens’ uniaxial compressive strengths and splitting tensile strengths; combined with the testing results of the intact specimens’ uniaxial compression and splitting test, analyze the fracture’s weakening effects and rock bolts’ strengthening effects on the specimens’ mechanical properties; summarize the disciplines of anchorage angle and rock- bolt number influencing the anchorage effects of the rock bolt(s) to the fractured specimens.Lastly, launch biaxial compressive test to intact specimens, fractured specimens, and anchored-fractured specimens; analyze fracture’s weakening effects and rock bolts’ strengthening effects on the specimens’ mechanical properties under different lateral pressures; summarize the disciplines of anchorage angle and rock- bolt number influencing the anchorage effects of the rock bolt(s) to the fractured specimens under different lateral pressures and study the influence of lateral pressure on different specimens’ biaxial compressive strengths.In addition, the specimens’ mechanical properties influenced by the rock-bolt number and anchorage angle are studied; the rock bolts’ failure patterns and its influences on the specimens’ destruction process are also observed.In the numerical simulation stage, the axial compressive experiment of the three kinds of specimens including intact specimens, fractured specimens and anchored-fractured specimens is simulated by FLAC-3D; obtain the different specimens’ numerical stress vs. strain curves, mortar’s contour of the minimum and maximum principle stress, and the stress or force state of the rock bolt(s). Use the included pile element of FLAC-3D to simulate the rock bolt(s) while simulating the anchored-fractured specimens’ axial compressive experiment. Adopt the two methods of solid-entity method and solid-entity and equivalence compounding method to simulate rock-bolt anchorage effect on the fractured specimens’ mechanical properties. The solid-entity and equivalence compounding method’s simulation result is much better than the solid-entity method in terms of multi-rock-bolt’s reinforcing effect comparing to the results of laboratory experiment. Besides, by taking the single-anchored fractured specimen’s axial compressive experiment as an example, one discipline of the anchorage angle influencing the anchorage effect is got by the simulation of FLAC-3D.The discipline about the rock bolt’s number and anchorage angle on rock-bolt anchorage effect to fractured specimens is obtained by summarizing the results of the laboratory experiment and numerical simulation. The results of this research will be significant for the practical engineering, since the materials’ mechanical and physical parameters used in laboratory experiment and numerical simulation are strictly accordant to a fixed similar ratio comparing the real materials.更多还原