本科毕业设计英文翻译
题 目 加拿大岩爆支护手册 青春期主题教育
学 院 水 利 水 电 学 院
专 业 水 利 水 电 工 程
学生姓名 尹 刚
学 号 0943062172 年级 09级
指导教师 张 茹
二Ο一三年六月三日
2.1Introduction
如影随行Explicit analysis of each potential rockburst-damage mechanism and the interaction between the rockmass and the support system are complex tasks. This chapter provides a summary of the key items found in this handbook such that the practitioner is provided with guidance for support lection in burst-prone ground without undertaking all of the analytical steps necessary to complete a detailed design. For this summary chapter, details of the analysis procedures have been omitted谁用英语怎么说, but they are described in subquent chapters.
Rockburst damage refers to damage that occurs around an excavation in a sudden or violent manner and is associated with a ismic event. Rockburst damage may not necessarily result in ejection of rock into the excavation, especially if the excavation is we
ll supported. The damage mechanisms associated with different types of rockbursts vary from situation to situation (Kair 1993; Ortlepp and Stacey 1940)马宇轩. The first step in dealing with support lection for burst-prone conditions is to estimate the type of damage mechanism involved and the likely verity of the resulting damage. Also it is uful to understand the conditions that lead to or trigger a rockburst.
2.2 What caus rockbursts?
For the purpos of hazard asssment and support design we distinguish between rockbursts that are triggered by remote ismic sources and rockbursts that are “lf-initiated”. For lf-initiated rockbursts, the location of the damage and the ismic event are the same.
2.2.1 Self-initiated rockbursts
Self-initiated rockbursts occur when the stress near the boundary of an excavation exceed the rockmass strength, and failure proceeds in an unstable or violent manner. Th
e stress generally increa as a result of nearby mining. In addition, the rockmass strength may degrade with time or with loss of confinement, leading to sudden failure. In either ca the rockmass strength-to-stress ratio reaches unity and the rock fails. The failure process is sudden and violent if the stored strain energy in the rockmass is not dissipated in a gradual manner. This occurs when the stiffness of the loading system,我的雅典娜>自然景象 i.e., the mine stiffness, is softer than the unloading stiffness of the volume of failing rock (Jaeger and Cook 1969; Brady and Brown 1993).
十三岁
短字成语Another form of lf-initiated rockburst is caud by a loss of structural stability. One example is the sudden buckling of a column or slab of rock. Structural instability usually leads to sudden failure but the conditions leading to failure are dependent on geometric considerations rather than the strength of the rock.
2.2.2 Remotely triggered rockbursts
Rockbursts triggered by remote, relatively large magnitude ismic events (e.g., fault slip) are a common occurrence in some hard rock mines, particularly during the later stages of the mine’s life and where faults interct stopes or large mined-out areas and sill pillars. A remote ismic event within a rockmass may create sufficiently high vibrations, and hence dynamic stress,near an underground opening to initiate rockburst damage. The incoming ismic wave may lead to fracturing of rock near an underground opening, or lead to structural instability (buckling), or directly provide sufficient energy to eject rock due to ismic energy transfer, rockburst hazard asssment involves determining the peak particle velocities induced in the rock around underground openings clo to the ismic source, i.e., generally within a few hundred metres (Chapter 5). However, meta-stable structures such as dykes and pillars may react to ismic events at larger distances (1000m).
2.2.3 Influence of mining stage
The nature of the mining-induced ismic activity and the associated rockbursts occurring
in a mine usually change throughout the mine’s life span. In some Canadian mines, significant ismic activity may not occur until most of the ore has been mined and extraction ratios are high.
Seismic activity occurring during the initial stages of a mine’s life is usually caud by high localized stress concentrations near drifts that are relatively isolated from each other. The magnitude of the ismic events associated with the failures is usually small (generally less than Nuttli magnitude 2 for Canadian mines). Strainbursts are often associated with localized stress rairs such as faults, dykes, and stiffer rock types.
As the mine matures, multiple openings and numerous stopes are created. Strainbursts may still occur. However, now that larger volumes of rock have become highly stresd, sudden failure of rock pillars (e.g., sill pillars) may occur. When such pillars fail suddenly, significant stored strain energy is relead from the hanging and footwall, and ismic activity with a moderate magnitude (around Nuttli magnitude 2) can occur. The maximum Nuttli magnitude for ismic events associated with pillar bursts in Ontario mines ems to be 3.5 (Hedley, pers. Comm. 1995).
During late stages of a mine’s life, regional changes in the stress are created, affecting large, mine-wide volumes of rock. This effect can initiate fault-slip ismic events with moderate to large ismic magnitudes (generally less than Nuttli magnitude 4 in Canada). Most importantly, the large events may be encountered where critically stresd faults interct stopes, becau a greater degree of freedom for movement along the fault has been created. Large ismic events may in tum trigger smaller localized rockbursts and ismically-induced rockfalls at multiple locations in the mine.
2.3 Rockburst damage mechanisms
Bad on our obrvations, rockburst damage is caud by one or more of the following mechanisms:
﹒Rock bulking due to fracturing
﹒Rock ejection due to ismic energy transfer
