Mapeo Geológico de un macizo rocoso

Presentación del tema: "Mapeo Geológico de un macizo rocoso"— Transcripción de la presentación:

1 Mapeo Geológico de un macizo rocoso

2 RQD (Rock Quality Designation)
Rock quality designation index (RQD) Rock Quality Designation index (RQD) fue desarrollado por Deere (Deere et al 1967) como una herramienta para estimar cuantitativamente la calidad del macizo rocoso a partir de testigos de sondaje. RQD es definido como el porcentaje de piezas intactas mayores a 10 cm en el largo total del sondaje. El testigo debe ser al menos de tamaño NW (diámetro 54.7 mm o 2.15 pulgadas) y debe ser perforado con barras de doble tubo.

3

4 Cuando no hay testigos disponibles, RQD puede ser estimado del número de discontinuidades por unidad de volumen: RQD = Jv (approx.), con Jv = númbero total de discontinuidades por m 3 (0 < RQD < 100 for 35 > Jv > 4.5).

5 RQD is a directionally dependent parameter and its value may change significantly, depending upon the borehole orientation. The use of the volumetric joint count can be quite useful in reducing this directional dependence. RQD is intended to represent the rock mass quality in situ. When using diamond drill core, care must be taken to ensure that fractures, which have been caused by handling or the drilling process, are identified and ignored when determining the value of RQD. When using Palmström's relationship for exposure mapping, blast induced fractures should not be included when estimating Jv. In the context of this discussion, the most important use of RQD is as a component of the RMR and Q rock mass classifications.

6 Rock Mass Classifications
RQD Geomechanics System - Rock Mass Rating (RMR) by Bieniawski (1984, 1989) Q-System - Norwegian Geotechnical Institute (Barton, et al. 1974) Geological Strength Index, GSI (Hoek, et al., 1995)

7 Rock Mass Rating (RMR) RMR basado en cinco parametros:
Resistencia uniaxial, qu RQD Espaciamiento de discontinuidades Condición de discontinuidades Condición de agua subterránea RMR = R1+R2+R3+R4+R5 Ajuste por orientación de discontinuidades relativo a la construcción Rock City Chattanooga, TN

8 Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
Rock Mass Rating (RMR) Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]

9 Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
Rock Mass Rating (RMR) Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]

10 NGI- Q Rating of Rock Masses
Q-Rating basado en 6 parametros: RQD Número de sets de discontinuidades, Jn Rugosidad de Discontinuidades, Jr Condición de discontinuidades/relleno, Ja Condición de agua subterránea, Jw Stress Reduction Factor, SRF Rating: Tucson, AZ

11

12 Geological Strength Index, GSI
Developed by Hoek, Kaiser, & Bawden (1995), Hoek & Brown (1997). GSI from Q-system: GSI from Geomechanics system where RMR > 25: Chart approach based on structure & surface quality

13 GSI Evaluation from Chart
Hoek (2000)

14 Strength of Rock Masses
Depends on Intact Rock Material and Rock Mass Jointing Intact Rock Uniaxial Compression Strength, qu = su Rock Material Type using parameter mi Fractured Rock Characteristics (in terms of GSI) Parameters mb and s and exponent "a" Obtain Mohr-Coulomb Strength Envelope from:

15 Rock Strength: mi parameter

16 Strength of Fractured Rock Masses
Parameter: mb = mi exp [(GSI-100)/28] For GSI > 25: s = exp [(GSI-100)/9] exponent a = 0.5 For GSI < 25: s = 0 exponent a = (GSI/200)

17 Strength of Fractured Rock Masses
Excel Spreadsheet of Generated Principal Stresses

18 Strength of Fractured Rock Masses

19 Strength of Fractured Rock Masses

20 Strength of Rock Masses
mi 

21 Strength of Rock Masses
c'/qu mi

22 Equivalent Modulus of Rock Masses (Table 10-7)

23 Allowable Bearing Stresses on Rock Masses

24 Intact Rock Strength Interrelationships

25 ER-qu Groups for Igneous Rocks
Deere and Miller (1966)

26 ER-qu Groups for Sedimentary Rocks
Deere and Miller (1966)

27 ER-qu Groups for Metamorphic Rocks
Deere and Miller (1966)

28 EMAX-qu Groups for All Types of Geomaterials
(Tatsuoka and Shibuya, 1992)