Type of Earthcache: Engineering with a geology theme (Engineering Geology).
Site Geology
The bedrock geology of the area is essentially granite, locally known as Kajang Granite that it is also part of the Kuala Lumpur Granite (Tajul Anuar Jamaluddin, 2011) which extent from Batang Kali and Rawang in the north, passes through Gombak, Ampang, Cheras, Hulu Langat and Kajang to Seremban in the south. The Kuala Lumpur Granite is part of the western flank of the Main Range Granite (Yin, 1976). Geochronological studies (Bignell & Snelling, 1977; Darbyshire, 1988) suggested that the age of the granite is around 215-199 million years or Late Triassic.
The Kajang Granite is composed mainly of medium- to coarse-grained, equigranular to moderately porphyritic textured, light grey muscovite-biotite granite. The granite consists predominantly of quartz, plagioclase, K-feldspar with some amount of biotite and muscovite (Tajul Anuar Jamaluddin, 2011).
Types of Rock Slope Failure
Most slope failures can be classified into one of four categories depending on the geometrical and mechanical nature of the discontinuity and the conditions of the rock masses as shown in Figure 1 (Terry and Kyu, 2007).
Circular failures occur when rock masses are highly fractured or composed of very weak material.
Planar failures occur when a discontinuity strikes parallel or nearly parallel to the slope face and dips into the cut slope at an angle greater than the friction angle which is the maximum angle before the rock mass will begin sliding.
Wedge failures involve a rock mass defined by two discontinuities with a line of intersection that is inclined out from the slope face where the inclination of the intersection line is significantly greater than the angle of friction.
Toppling failures involve rock slabs or columns defined by discontinuities that dip steeply into the slope face.
Figure 1: Four types of rock slope failure (a) Circular Failure (b) Planar Failure (c) Wedge Failure (d) Toppling (modified from Hoek and Bray, 1981). The circular diagrams on the right are stereographic plots that show the orientations of the discontinuities; they are not relevant to the understanding of the types of rock slope failure in this Earthcache.
How to claim this EarthCache?
From the given coordinates, look at about 40° inclination in the direction of 000° (N). You will see a scar on the rock face as evidence of rock that has fallen off. Examine the planes/discontinuities of the rock failure exposed by the scare. Based on Figure 1, identify the type of failure.
Next go to Additional Waypoint KGQ, look at the rock face of highly persistent joint sets and numerous loose, overhanging blocks. The dominant joint sets strike 310° (NW). Based on Figure 1, identify the type of failure. Also, note that due to this type of failure, there are numerous occurrences of rock falls at the base of the slope.
Email me the following;
1. The text "GC7CJH9 Kajang Rocks Quarry - Granite" on the first line.
2. The answers to the following questions;
- Name the type of failure you observed at the Earthcache coordinates.
- Name the type of failure you observed at the Additional Waypoint KGO.
3. Provide a photo of yourself or a personal item to prove you have visited the site.*
References
1 Bignell, J.D. & Snelling, N.J., 1977. Geochronology of Malayan Granites. Overseas Geological Mineral Resources, London, 47, 73p. 2 Darbyshire, D.P.F., 1988. Geochronology of Malaysian granites. NERC Isotope Geological Centre Report, no. 88/3. 3 Hoek, E. and Bray, J. W., 1981. Rock Slope Engineering, revised 3rd ed. Institute of Mining & Metallurgy, London, 358p. 4 Tajul Anuar Jamaluddin, 2011. Engineering geology and rock slope stability for developments in former granite quarry sites (Field trip guide). IGM Professional Short Course Series – Engineering Geology of Rock Slopes, UKM, Bangi, Selangor. 5 Terry, R.W. and Kyu, H.C., 2007. Rock slope stability of the VMT. Prepared for the Prince William Sound Regional Citizen’s Advisory Council (RCAC). PWSRCAC commissioned report, [online] Available at: http://www.pwsrcac.org/docs/d0039900.pdf [Accessed 25 December 2011].
6. Yin, E.H., 1976. The geology and mineral resources of the Kuala Lumpur Area. Geological Survey Malaysia Manuscript.
* Effective immediately from 10 June 2019, photo requirements are permitted on EarthCaches. This task is not optional, it is an addition to existing logging tasks! Logs that do not meet all requirements posed will no longer be accepted.
For additional information, visit; Geosociety.org, Geocaching.com Help Center and Geocaching.com Forum.
Finding the answers to an EarthCache can often be challenging, and many people tend to shy away from these caches because of this. However, it is my opinion that geocaching is also meant to be a fun family experience that simply aims to introduce interesting and unique locations such as this one. Flexibility on logging requirements, however, can only be applied if it can be established that you have actually taken the time to visit the site. For this reason, a proper log describing your adventure accompanied by a good number of photos would be much appreciated.
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