ISSN:0094-8276    

DOI:10.1029/GL008i007p00645

年代:1981

数据来源: WILEY

摘要:

Because virtually all tectonophysical processes are masked by the overburden, or occur too slowly for adequate observation in anthropocentric time, or both, they must be studied in carefully controlled laboratory experiments that simulate the natural environment as realistically as is practicable. Extrapolations of laboratory data in space and time are invalid unless the experimental and natural phenomenologies are essentially the same. The size of conventional specimens is of the order of 10 cm, whereas the discontinuities (defects in a continuum) in real rock‐masses are often much larger, of the order of l m of more. Furthermore, such discontinuities as macrofractures (joints) may well dominate the mechanical and fluid‐transport properties in nature. Adequate sampling of rock‐mass properties will probably always requirein‐situtesting, but testing machines much larger than any now available could provide useful data at least at intermediat

ISSN:0094-8276    

DOI:10.1029/GL008i007p00647

年代:1981

数据来源: WILEY

摘要:

Strength of certain soft rocks decreases about tenfold as specimen size reaches around 1 meter; at still larger sizes, it appears to remain constant. Hard rocks have not been tested over this range of sizes, so their size effect is unknown. Elastic modulus of unfractured rocks is only very slightly dependent on specimen size up to a meter. However, large fractured samples may be five to ten times more compliant than small intact samples. Friction is also size‐dependent, although observations are conflictin

ISSN:0094-8276    

DOI:10.1029/GL008i007p00651

年代:1981

数据来源: WILEY

摘要:

Potential research applications for large‐specimen geophysical experiments include measurements of scale dependence of physical parameters and examination of interactions with heterogeneities, especially flaws such as cracks. In addition, increased specimen size provides opportunities for improved recording resolution and greater control of experimental variables. Large‐scale experiments using a special purpose low stress (10

ISSN:0094-8276    

DOI:10.1029/GL008i007p00653

年代:1981

数据来源: WILEY

摘要:

Geochemical problems that would benefit from large scale experiments include: 1) the determination of the physical properties of the many common rocks that are chemically homogeneous on the scale of 5‐100 cm but not on a scale of 1‐5 cm, 2) the study of the influence of rock textures and compositions and of the chemistry of the pore solution on stress corrosion cracking, and 3) the study of chemical transport within gradients in temperature, chemical potentials and stress. The ultimate goal of a few well‐chosen large scale studies should be the development of predictive m

ISSN:0094-8276    

DOI:10.1029/GL008i007p00657

年代:1981

数据来源: WILEY

摘要:

Laboratory studies on fluid flow in single fractures in rock samples up to a meter in size suggest that there is a definite problem of scale. Two such studies have been reported, but the results are not consistent. The seemingly contradictory results may simply be a manifestation of the effects of fracture surface roughness. A basic problem in attempting to understand the physics of fluid flow in fractures is that of understanding the effects of surface roughness. The investigations that are envisioned to attack this problem will only be possible on rock samples that are much larger than the conventional size.

ISSN:0094-8276    

DOI:10.1029/GL008i007p00659

年代:1981

数据来源: WILEY

摘要:

The potential application of large scale geomechanical testing results to the following five mining/civil engineering problem areas; roof spans, design of rock support‐reinforcement systems, design of rock compression members, development/optimization of fragmentation systems, and design of slopes is discussed. It is concluded that such testing does have an application but to be meaningful it must be accompanied by significant field observation measurement programs.The type of testing facility required is not universal but depends upon the problem to be examine

ISSN:0094-8276    

DOI:10.1029/GL008i007p00663

年代:1981

数据来源: WILEY

摘要:

Marked strength‐size effects are observed when joints are subjected to shear. This is due to the mobilization of larger, but less steeply inclined asperities as sample size is increased. The displacement required to mobilize strength is also increased by the changing size of sample. These observed size effects indicate that large scale tests should be performed to obtain realistic data concerning shear behavior, dilation, and associated permeability change

ISSN:0094-8276    

DOI:10.1029/GL008i007p00667

年代:1981

数据来源: WILEY

摘要:

Empirical relations between size and strength have found ample treatment in the literature, not so the effect of size on the underlying mechanism. This paper examines size effect on fracture mechanism in unconfined and triaxial tests between intact specimens of various sizes and on jointed specimens with various spacings. Statistical size effect and volume dependent strain energy effect can be distinguished and are shown to differently affect crack propagation and failure mechanism.

ISSN:0094-8276    

DOI:10.1029/GL008i007p00671

年代:1981

数据来源: WILEY

摘要:

Although in situ tests have the advantage of involving a large volume or rock tested under the same environmental conditions as are prevailing in the rock mass, such tests are expensive and time consuming. In addition, there are a number of controversial questions pertinent to in situ tests.This presentation discusses the first‐hand experience with three in situ test methods. These are: (i) plate bearing tests, (ii) large and small flat jack tests, and (iii) Goodman jack tests. By identifying the problems associated with in situ testing, useful lessons can be learned for large scale laboratory testing in geomechanic

ISSN:0094-8276    

DOI:10.1029/GL008i007p00675

年代:1981

数据来源: WILEY