ASTM D5335-2008
用粘结的电阻应变仪测定岩石热膨胀线性系数的标准试验方法

Standard Test Method for Linear Coefficient of Thermal Expansion of Rock Using Bonded Electric Resistance Strain Gauges

标准号

ASTM D5335-2008

发布日期

2008年

实施日期

废止日期

无

中国标准分类号

P13

国际标准分类号

93.020 (Earth works. Excavations. Foundation const

发布单位

US-ASTM

适用范围

Information concerning the thermal expansion characteristics of rocks is important in the design of any underground excavation where the temperature of the surrounding rock may be altered. Thermal strain causes thermal stress that ultimately affects the stability of underground excavations. Examples of applications where rock thermal strain is important include: nuclear waste repositories, underground power stations, compressed air energy storage facilities, and geothermal energy facilities.

The linear coefficient of thermal expansion, x03B1;, of rock is known to vary as the temperature changes. Rock thermal strain is normally not a linear function of temperature. This test method provides a procedure for continuously monitoring thermal strain as a function of temperature. Therefore, information on how a changes with temperature is obtained.

Other methods of measuring the expansion coefficient of rock by averaging the thermal strain of a large specimen over a temperature range of many degrees may result in failure to determine the variation in x03B1; of that rock for one or more of the following reasons:

Alpha is not always linear with temperature,

Some rocks are anisotropic having directional characteristics which can vary by more than a factor of two.

Alpha may have a negative value in one direction and, at the same time, a positive value in the others.

Strain gauges, both wire and foil types, have been successfully employed to measure the thermal expansion coefficients of rock. These coefficients are frequently very small, being on the order of millionths of a millimetre per millimetre for each degree Celsius (millionths of an inch per inch for each degree Fahrenheit). The thermal strain of rocks is about one tenth that of plastics and one half or one quarter that of many metals. Therefore, measurement methods for rocks require greater precision than methods that are routinely used on plastics and metals.

Note 48212;Notwithstanding the statements on precision and bias contained in this test method; the precision of this test method is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D 3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D 3740 provides a means of evaluating some of those factors.

1.1 This test method covers the laboratory determination of the linear (one-dimensional) coefficient of thermal expansion of rock using bonded electric resistance strain gauges.

1.2 This test method is applicable for unconfined pressure conditions over the temperature range from 20 to 260x00B0;C (68 to 500x00B0;F).

Note 18212;Unconfined tests performed at elevated temperatures may alter the mineralogy or grain structure of the test specimen. This alteration may change the physical and thermal properties of the test specimen.

Note 28212;The strain gauges are mounted with epoxy. Most commercially available high temperature epoxies require elevated temperature curing. The elevated temperature required for this curing may alter the physical and thermal properties of the test specimen. Epoxy should be selected based upon the maximum expected test temperature. Room temperature curing epoxy should be used whenever possible.

1.3 The test specimens may be either saturated or dr......

ASTM D5335-2008 中可能用到的仪器设备