Large Scale Tests on Jointed and Bedded Rocks Under Multi-Stage Triaxial Compression and Direct Shear

2014 ◽  
Vol 48 (1) ◽  
pp. 75-92 ◽  
Author(s):  
Maximiliano R. Vergara ◽  
Peter Kudella ◽  
Theodoros Triantafyllidis
Keyword(s):  
Large Scale ◽  
Triaxial Compression ◽  
Direct Shear ◽  
Multi Stage ◽  
Large Scale Tests ◽  
Bedded Rocks

Comparison of shear strength of sand backfills measured in small-scale and large-scale direct shear tests

2008 ◽  
Vol 45 (9) ◽  
pp. 1224-1236 ◽  
Author(s):  
Christopher A. Bareither ◽  
Craig H. Benson ◽  
Tuncer B. Edil
Keyword(s):  
Large Scale ◽  
Triaxial Compression ◽  
Particle Diameter ◽  
Small Scale ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Failure Envelopes ◽  
Significant Difference ◽  
Backfill Materials

Direct shear tests were conducted on 30 sand backfill materials having gravel contents ranging from 0% to 30% in a 64 mm square small-scale direct shear (SSDS) box and a 305 mm square large-scale direct shear (LSDS) box. The objectives were to compare the shearing behavior of a broad range of natural sand backfill materials tested in SSDS and LSDS and to determine if the same friction angle (φ′) is obtained in SSDS and LSDS when the natural backfill material contains gravel. Triaxial compression (TC) tests were also conducted on four of the backfill materials for comparison with the SSDS and LSDS tests. Specimens tested in SSDS and TC included only material passing the No. 4 sieve (P4). Test specimens in LSDS included the P4 material as well as material retained on the No. 4 sieve (R4), to a maximum particle diameter of 25.4 mm. Friction angles corresponding to peak strength (φ′) measured in SSDS and LSDS differed by no more than 4° for a given sand backfill, and in most cases were within 2°. The friction angles also were unaffected by removal of the R4 material. Repeatability tests showed that statistically similar failure envelopes (p-value = 0.98) are obtained in SSDS and LSDS, and that highly repeatable friction angles (φ′) are obtained using the SSDS (φ′ ± 0.25°) and the LSDS (φ′ ± 0.45°) methods. No statistically significant difference was found among the failure envelopes measured in SSDS, LSDS, and TC, suggesting that φ′ for clean sand backfill with less than 30% gravel can be measured with similar accuracy using any of the three test methods.

scholarly journals Direct Shear Test on Coarse Gap-Graded Fill: Plate Opening Size and Its Effect on Measured Shear Strength

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
H. Cai ◽  
R. Wei ◽  
J. Z. Xiao ◽  
Z. W. Wang ◽  
J. Yan ◽  
...  
Keyword(s):  
Shear Strength ◽  
Large Scale ◽  
Fine Particles ◽  
Triaxial Compression ◽  
Direct Shear ◽  
Test Results ◽  
Compression Tests ◽  
Construction Sites ◽  
Direct Shear Tests ◽  
Soil Mixtures

In this paper, three different rock-soil mixtures were reconstituted in laboratory, which were designed to mimic the proportions of coarse and fine particles in the high fill used at the airport construction sites. The shear strength of the reconstituted mixtures was determined by both large-scale direct shear tests (DSTs) with different plate opening sizes and triaxial compression tests. By comparing the test results, the most appropriate plate opening size for DSTs on coarse gap-graded rock-soil mixtures is discussed. The test results indicate that the opening size has a significant effect on the measured shear strength of gap-graded rock-soil mixtures. For DSTs under the same normal stress, the peak strength decreases with increasing plate opening size. For the gap-graded mixture with a small proportion of coarse particles, a plate opening size of one-third to one-quarter of the maximum particle size (dmax) is suitable. With a higher coarse particle content, the opening size should be increased appropriately. If the percentage of gravels (5.0 mm < d < 20.0 mm) is more than 47%, a plate opening size of slightly greater or less than one-half dmax is more appropriate.

Two key switches in regional stress field during multi-stage deformation in the Carboniferous−Triassic southernmost Altaids (Beishan, NW China): Response to orocline-related roll-back processes

2021 ◽  
Author(s):  
Zhonghua Tian ◽  
Wenjiao Xiao ◽  
Brian F. Windley ◽  
Peng Huang ◽  
Ji’en Zhang ◽  
...  
Keyword(s):  
Stress Field ◽  
Large Scale ◽  
Electron Backscatter Diffraction ◽  
Volcanic Rocks ◽  
Structural Deformation ◽  
Regional Stress ◽  
Regional Stress Field ◽  
Multi Stage ◽  
Beishan Orogenic Collage ◽  
Roll Back

The orogenic architecture of the Altaids of Central Asia was created by multiple large-scale slab roll-back and oroclinal bending. However, no regional structural deformation related to roll-back processes has been described. In this paper, we report a structural study of the Beishan orogenic collage in the southernmost Altaids, which is located in the southern wing of the Tuva-Mongol Orocline. Our new field mapping and structural analysis integrated with an electron backscatter diffraction study, paleontology, U-Pb dating, 39Ar-40Ar dating, together with published isotopic ages enables us to construct a detailed deformation-time sequence: During D1 times many thrusts were propagated northwards. In D2 there was ductile sinistral shearing at 336−326 Ma. In D3 times there was top-to-W/WNW ductile thrusting at 303−289 Ma. Two phases of folding were defined as D4 and D5. Three stages of extensional events (E1−E3) separately occurred during D1−D5. Two switches of the regional stress field were identified in the Carboniferous to Early Permian (D1-E1-D2-D3-E2) and Late Permian to Early Triassic (D4-E3-D5). These two switches in the stress field were associated with formation of bimodal volcanic rocks, and an extensional interarc basin with deposition of Permian-Triassic sediments, which can be related to two stages of roll-back of the subduction zone on the Paleo-Asian oceanic margin. We demonstrate for the first time that two key stress field switches were responses to the formation of the Tuva-Mongol Orocline.

SYNTHETIC PHEROMONES DISRUPT MALE DIORYCTRIA SPP. MOTHS IN A LOBLOLLY PINE SEED ORCHARD

2000 ◽  
Vol 132 (3) ◽  
pp. 345-351 ◽  
Author(s):  
Gary L. DeBarr ◽  
James L. Hanula ◽  
Christine G. Niwa ◽  
John C. Nord
Keyword(s):  
Loblolly Pine ◽  
Large Scale ◽  
Sex Pheromones ◽  
Mating Disruption ◽  
Seed Orchard ◽  
Control Treatment ◽  
Tetradecenyl Acetate ◽  
Lepidoptera Pyralidae ◽  
Trap Catches ◽  
Large Scale Tests

AbstractSynthetic sex pheromones released in a loblolly pine, Pinus taeda L. (Pinaceae), seed orchard interfered with the ability of male coneworm moths, Dioryctria Zeller spp. (Lepidoptera: Pyralidae), to locate traps baited with sex pheromones or live females. Pherocon 1C® traps baited with synthetic pheromones or live conspecific females were hung near the center of two 1.2-ha circular plots during emergence of Dioryctria amatella (Hulst), Dioryctria disclusa (Heinrich), and Dioryctria merkeli (Mutuura and Munroe). In a paired design, trap catches for the mating-disruption treatment with synthetic pheromone dispensers consisting of three polyvinyl chloride rods placed in every tree were compared with the control treatment. Treatments were alternated at intervals of 2–3 d. Trap catches of D. amatella were reduced by 91% when plots were treated with 2.5 g/ha of Z-11-hexadencenyl acetate. Catches were reduced by 99.5% for D. disclusa and by 97% for D. merkeli when plots were treated with 12.5 g/ha of Z-9-tetradecenyl acetate, whereas catches of D. amatella were unaffected by this mating-disruption treatment. Daily disappearance of Z-9-tetradecenyl acetate from the dispensers averaged 0.46 g/ha or less. Manually placing dispensers on nylon lines in the tops of trees was an effective method for releasing synthetic Dioryctria pheromones in the orchard. These data suggest it may be feasible to prevent mating of Dioryctria spp. in pine seed orchards by using synthetic pheromones for mating disruption, but large-scale tests will be required to demonstrate cone protection.

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