Rock-anchoring

Fig. 7.7. Load v bonded length for end bonded rock anchors (courtesy of Celtite (Selfix) Ltd).

Measures to control rockfall include catch fences, benches, wire mesh and rock traps. Restraining structures control landslides by increasing the resistance to movement. They include, for example, retaining walls, reinforced earth structures, shotcrete, cribs, gabions, buttresses, piling, dowels, rock bolts and rock anchors (see Chapter 9). The following minimum information is required to determine the type and size of a restraining structure ... 

In connection with shotcrete, wetting agents may also have an impact on occupational dermatology, because, among other substances, they may contain polyacrylates. When rock anchors are used (to secure the rock), considerable quantities of epoxy resin... 

Habel, W.R. Long-term monitoring of 4,500 kN rock anchors in the Eder gravity dam using fibre-optic sensors. Proc. Int. Symp. Geotechnical Measurements and Modelling, Balkema, ISBN 90 5809 603 3 (2003), pp. 347-354... 

TABLE 9.8 Typical Values of Bond Stress of Rock Anchors for Selected Rock... 

A tie back system can be combined with any of the above cantilever systems to create a more efficient retraining wall. Soil nails and rock anchors are the most commonly used tie back elements. Any other... 

These construction methods are normally executed to designs prepared by specialist contractors and can embody various features to ensure safety. For example, soil or rock anchors used as tie-backs are tested by loading each one to an ar-... 

Schlieren /.pi. schlieren (regions of varying refraction, as in liquids) streaks, striae, schlieren (as in glass and igneous rocks). -ver-fahren n. (Photog.) schlieren process. schHerig a. streaked, striated, banded. Schliesse /. pin, peg, catch, anchor, clasp, schliessen, v.t. close shut, lock seal (tubes) bind embrace contract conclude. — v.r. close be related, be apropos. — v.i. close. 

Often, however, the sample does not lend itself to measurements of multiple phases. In these cases, one can create a model isochron in which the initial isotopic ratio of the daughter element (D(/Dref) is assumed and is used to anchor the -intercept. With this assumption, a single measurement can provide the initial ratio [(NR/Ns)o of an object. A third type of isochron diagram makes the assumption that a group of bodies all formed from the same homogeneous isotopic reservoir at the same time. This whole-rock isochron is constructed from bulk measurements of each sample, and the resulting slope and initial ratio describe the reservoir from which all of the samples formed. 

A number of insects and other invertebrates create thin fibers, for a variety of reasons. Spiders make webs for support and to capture and encase their prey. Some bivalve mollusks create byssal threads that anchor the animal s shell to rocks or other substrate. 

To determine the age of these objects, archaeologists had to develop new strategies. Although pottery phases and stratigraphy (the analysis of the origin, distribution, and succession of layers or strata of earth) can be used to date objects found on land, neither technique works reliably for objects found in the sea, where water may distort the shape of a jar or may carry away rocks and silt from the scene of the wreck. Instead, archaeologists use anchors (and sometimes ship nails) to determine the age of a shipwreck. Like pottery, anchors were produced in different sizes and shapes and made of different kinds of materials (such as stone or iron) that conform to histori-... 

Anchoring systems are materials used mainly for securing bolts, bars, tendons or dowels in drilled or formed holes in concrete, masonry or natural rock. Polyester anchors are widely used because of their fast curing property and high early strength (Fosroc International, undated a). Epoxy anchors are applied in areas where there is a risk of alkaline hydrolysis. 

Anchoring grout controllable setting time rapid strength gain corrosion resistance Securing bolts, bars, tendons or dowels in drilled or formed holes in concrete masonry or natural rock... 

Lay them over the row or bed, leaving enough slack to allow plants to grow underneath. Anchor the edges with soil, rocks, boards, bricks, or other heavy objects. You can make or buy hoop supports for delicate crops like baby lettuce that may be damaged by abrasion. Later, remove the covers temporarily to thin plants, weed, or harvest. In the spring, periodically check for aphid infestations. 

Mechanical rock bolts are steel rods fitted with expanding end pieces which are anchored into a drilled hole. The exposed end of the rod is threaded, and fitted with a large plate (which acts as an oversized washer), and a heavy nut with which tension is applied to the bolt. The applied tension then compresses the rock, reducing or eliminating the tendency to spall or cave. Mechanical rock bolts come in a number of different configuration and lengths, but they all function in the same manner. They must be spaced so that the zones of compression of adjacent bolts overlap. Rock bolts have a long history of use, particularly in coal mines. 

Polyesters and expoxies have been used to seal cracks in rock formations and to anchor rock reinforcement members in drilled holes. The mechanical properties of these materials are much better than those of Portland cement. However, the chemicals are (relative to other grouts) very expensive and very viscous. Rendering them less viscous by using diluents so that they will penetrate sands makes them even more expensive. Because of their limited application as grouts, polyesters and epoxies are not detailed further. 

Other than in the early stage of heating and regardless of the rock-mass properties or failure criteria used, the anchor displacements relative to the MPBX assembly head, located at the collar of the heated drift, were larger for the anchors located farther away from the heated drift. This displacement pattern indicated that the neighboring anchors of an MPBX continued to move away from each other as heating proceeded, suggesting an expansion of the rock mass between the two anchors. This behavior was not strictly observed in the... 

The comparison is plotted in Figure 4 for 60° inclined boreholes (BH 147, 148, 154, 155, 178 and 179). The noticeable spread of the results may be attributed to the local rock mass heterogeneities, such as fractures. With the exception of the very early time, simulated displacements are within the range of the measured ones. The best agreement is obtained for Anchors 2 and 3, whereas the... 

---