PENGUJIAN IN SITU BATUAN

SCHMIDT (REBOUND) HAMMER

The Schmidt rebound hammer is principally a surface hardness tester. It works on the principle that the rebound of an elastic mass depends on the hardness of the surface against which the mass impinges. There is little apparent direct theoretical relationship between the strength of concrete and the rebound number of the hammer. However, within limits, empirical correlations have been established between strength properties and the rebound number.

Although the rebound hammer does provide a quick, inexpensive method of checking the uniformity of concrete, it has some serious limitations. The results are affected by:

Smoothness of the test surface Size, shape and rigidity of the specimen Age of the specimen Surface and internal moisture conditions of concrete Type of coarse aggregate Type of cement Carbonation of the concrete surface

(sumber : http://www.ahamgeo.com/schmidt.html)

Uji Palu Schmidt mula-mula dikembangkan untuk menentukan kekuatan kompresif konkret, secara luas digunakan untuk menentukan kekuatan batuan.Alat ini tidak bersifat merusak batuan, terdiri dari piston berpegas yang mengalami kontak antara permukaan batuan dengan logamnya.

Pantulan pada piston palu yang mengandung pegas setelah ditekan pada permukaan batuan dapat dibaca secara langsung dari alat berupa Schmidt Hammer Value (SHV) dan berhubungan dengan kekerasan.Empat tipe palu yang tersedia memiliki energi pantulan yang berbeda.Kekuatan batuan setiap tingkat pelapukan diperoleh sebagai data empiris melalui pantulan ini.Penting untuk diketahui alat ini sedikit tidak bekerja pada batuan yang memilki nilai pantulan kurang dari 10.

(sumber : http://hujungdestinasi.wordpress.com/2013/02/26/referat/)

BLOCK SHEAR METHODE

Types of Shear Tests

The type of specimen and the type of test tool involved in determining shear strengths were considered to be the most important factors influencing the result of the shear test. The cube-shaped specimen and the notched specimen were of particular interest as well as the tools equipped with roller bearings and those without such bearings. 2 3 4 Six test methods, including some standard methods, and some nonstandard methods, were proposed for study. The description of each is given in table 1, and the specimens and apparatus are shown in figures 1, 2, and 3. An examination of table 1 shows that test types A and C differ only in the location of the test. The standard British shear test used in 1929 was revised to the present type of test in 1938. It was intended at the outset of the study that test types B and E also differ only in location, but a misunderstanding as to type of apparatus led to the difference indicated.

Test Procedures

In testing at the U.S. Forest Products Laboratory, specimens were seated in the shear tool with an initial load of 200 pounds and then loaded at constant speed of about 0.024 inch per minute until failure occurred. The maximum load and the elapsed time from initial load to maximum load were recorded for each specimen. The weight and volume of each specimen were measured immediately before testing as a basis for specific gravity determination. Moisture content was determined by weighing and ovendrying the smaller piece of the broken shear specimen immediately after the test. Similar procedures were followed at the C.S.I.R.O. laboratory, except that elapsed time was not recorded.

(sumber : http://caritambangbatubara.com/2010/11/28/uji-mekanika-batuan-in-situ/)

In-Situ Shear Strength of Rock-Concrete Contact Surface at the Abutments of a Concrete Dam

The required equipment for cutting and preparing of test blocks includes an electrical saw, handy cutting tools such as hammer and chisel, solid casts in suitable dimensions and concrete additives. The equipment used for conducting the tests includes a 200 tones hydraulic jack and two 100 tones jacks for applying normal and shear loads, respectively. These jacks are fed with handy and/or electrical pumps. In order to prevent rotation of blocks under the tests, the shear load is applied with an angle of 15 degrees to the shear surface so that the load effect line is passing through the center of test block (figure 1 and 2). Normal load is also applied regularly and kept exactly normal to shear surface throughout the tests using rollers with low friction. Shear and normal loads are controlled using hydraulic gauges with the accuracy of 0.5 bars. In order to measure normal displacement, four mechanical or electrical gauges are used with the accuracy of 0.01 mm or 1 micron, respectively. For measuring lateral and shear deformation, 4 gauges of the same type are used. General lay out of the test.