Abstract
In this study, we investigated the preconsolidation pressure (P C) of sedimentary soft rock and its relationship with brittle-ductile transition (BDT) pressure. We proposed a generalized preconsolidation pressure (P G) suitable for both soil and sedimentary soft rock, which is defined in terms of the yield stress of the initial sediment structure under confined lateral compression. We then explored the digenetic effect on P G using 24 sediment types. Next, P G and BDT pressure were verified using confined compression and conventional triaxial tests, respectively, on red-bed soft rock in the Dingxi region of China. Finally, we discussed the BDT mechanism and analyzed the relationship between the two characteristic pressures for a given initial yield surface considered structural strength. We found that the relationship was dependent on the strength parameters, the initial structural strength, and the coefficient of earth pressure at rest. The findings of this study will have a significant impact on the determination of BDT pressure of sedimentary rock in future studies.
Highlights
Brittle-ductile transition pressure, generalized preconsolidation pressure, sedimentary soft rock, initial yield surface, coefficient of earth pressure at rest
The relationship between the brittle-ductile transition (BDT) pressure and PG of a sedimentary soft rock depends on its strength parameters, the initial structural strength, and the coefficient of earth pressure at rest
We explored the relationship between PG and BDT pressure by conducting experiments on Dingxi red-bed soft rock
Summary
Based on the strain softening and strain hardening behavior of OC and NC soils, Nygard et al (2004; 2006) and Gutierrez et al (2008) first determined in laboratory studies that the value of BDT pressure is close to that of apparent PC. These findings were later applied to evaluate the sealing characteristics of cap rocks (Liu et al 2018), and the exploration and production of shale gas (Yuan et al 2017), with satisfactory results. The main objectives of this study were to 1) investigate the PC of sedimentary soft rock, 2) propose a generalized concept of PC (PG) valid for both soil and sedimentary rock, and 3) explore the relationship between the PG and BDT pressure of sedimentary soft rock
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