1、英文原文:The Relation Between In situ and Laboratory RockProperties Used in Numerical Modelling1.INTRODUCTIONNumerical models are being used increasingly for rock mechanics design as cheaper and more efficient software and hardware become available. However, a crucial step in modelling is the determinat
2、ion of rock mass mechanical properties, more precisely rock stiffness and strength properties.This paper presents the results of a review of numerical modelling stiffness and strength propertiesused to simulate rock masses. Papers where laboratory and modelling properties are given have been selecte
3、d from the mass of more general modelling literature. More specifically papers that have reduced stiffness and/or strength parameters from laboratory to field values have been targeted. The result of the search has been surprising: of the thousands of papers on numerical modelling, a few hundred men
4、tion laboratory and rock mass properties, and of those, only some 40 appear to apply some kind of reduction. The papers that apply a reduction have been used to produce the graphs that constitute the main content of this paper. Rock stiffness properties have been separated from those of strength in
5、the analysis and this has illustrated interesting differences in their respective average reduction factors.2.METHODOLOGYThe review conducted has studied case histories and back analysis examples of numerical modelling for a wide range of rock structures. Each reviewed paper has been databased in te
6、rms of laboratory measured rock properties and numerical modelling rock mass input properties plus other relevant quantitative data 1-37.The vast majority of papers have provided incomplete data either omitting key parameters or synthesizing parameters. Some papers have given laboratory and mass pro
7、perties, and a few papers have explained the process by which laboratory properties have been adjusted to the rock mass by use of rock mass ratings. One can only conclude that this is related to the origin of the models or modellers, being from environments where materials like steel have no scale e
8、ffects. There would be few rock mechanics specialists who would not acknowledge that even the strongest rock types need some adjustment of their rock mass properties. The graphs and data provided in this paper have therefore concentrated on papers where reductions have been applied. A list of the mo
9、st valid and relevant numerical papers is included at the end of the paper.3.RESULTSFigure 1 presents the Youngs modulus results for laboratory tests plotted with those used in the model. Each case is numbered against its source. There is a simple trend in these data and if a straight line is fitted
10、, model stiffness is on average 0.469 of the laboratory stiffness (Fig. 2). The data can alternatively be plotted as reduction factors as in Fig. 3. Here a trend of increased reduction factors for low stiffness rock types becomes apparent. A number of very high reduction factors can also be seen for
11、 very low stiffness rocks. Figure 4 shows the uniaxial compressive strength results for laboratory tests plotted against those used in the model. Each case is numbered against its source. There is a simple trend in these data and, if a straight line is fitted, model strength is on average 0.284 of t
12、he laboratory strength (Fig. 5). The data can alternatively be plotted as reduction factors as in Fig. 6. Here, a trend of increased reduction factors for weak rock types becomes apparent. Figure 7 illustrates the trend for tensile strength, indicating that the laboratory values are reduced by a fac
13、tor of almost two and Fig. 8 shows the trend for Poisons ratio with no significant conclusions to be drawn.4.TECHNIQUES OF REDUCTIONA number of authors have presented relations between laboratory and in situ properties. Some have included rock mass ratings in their relations. The widely used techniq
14、ue to derive deformation moduli is equation (1) presented by Bieniawski 38 for rocks having a Rock Mass Rating (RMR) greater than 50 with a prediction error of 18.2%. However, when the RMR is less than or equal to 50, the Bieniawski formula is not applicable as it leads to values of deformation modu
15、li less than or equal to zero. Serafim and Pereira 39 using the Bieniawski Rock Mass Classification system (RMR) derived an alternative expression, equation (2), for the entire range of RMR.(1)(2)Figure 9 shows both the expressions plotted against the stiffness data from the review. A double x axis
16、has been used to compare these data. This has required the RMR to be related to laboratory E. A simple linear relation has been used over the typical full of both properties. (RMR = 0-100 and E = 0-120 GPa.) Nicholson and Bieniawski 40, have developed an empirical expression for a reduction factor, equation (3). This factor is calculated in order to derive deformation moduli for a rock mass using its RMR and a laboratory Youngs modulus.(3)Mitri et a
