Characterizing Permanent Deformation of Silty Sand Subgrades by Using a Model Based on Multistage Repeated-Load Triaxial Testing

2016 ◽  
Vol 2578 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Farhad Salour ◽  
Mohammad Shafiqur Rahman ◽  
Sigurdur Erlingsson
Keyword(s):  
Permanent Deformation ◽  
Silty Sand ◽  
Triaxial Testing ◽  
Model Based ◽  
Repeated Load ◽  
Repeated Load Triaxial

Geogrid Stabilization of Unbound Aggregates Evaluated Through Bender Element Shear Wave Measurement in Repeated Load Triaxial Testing

2020 ◽  
Vol 2674 (3) ◽  
pp. 113-125
Author(s):  
Mingu Kang ◽  
Joon Han Kim ◽  
Issam I. A. Qamhia ◽  
Erol Tutumluer ◽  
Mark H. Wayne
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Resilient Modulus ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Bender Element ◽  
Wave Measurement ◽  
Repeated Load ◽  
Repeated Load Triaxial

This paper describes the use of the bender element (BE) shear wave measurement technology for quantifying the effectiveness of geogrid stabilization of unbound aggregate materials with improved mechanical properties from repeated load triaxial testing. Crushed stone aggregate specimens were prepared with three different gradations, that is, upper bound (UB), mid-range engineered (ENG), and lower bound, according to the dense graded base course gradation specification in Illinois. The specimens were compacted at modified Proctor maximum dry densities and optimum moisture contents. Two geogrids with different triaxial aperture sizes were placed at specimen mid-height, and unstabilized specimens with no geogrid were also prepared for comparison. To measure shear wave velocity, three BE pairs were placed at different heights above geogrid. Repeated load triaxial tests were conducted following the AASHTO T307 standard resilient modulus test procedure, while shear wave velocity was measured from the installed BE pairs. After initial specimen conditioning, and at low, intermediate, and high applied stress states, both the resilient moduli and accumulated permanent strains were determined to relate to the geogrid local stiffening effects in the specimens quantified by the measured shear wave velocities. The resilient modulus and shear wave velocity trends exhibited a directly proportional relationship, whereas permanent strain and shear wave velocity values were inversely related. The enhancement ratios calculated for the geogrid stabilized over the unstabilized specimens showed significant improvements in mechanical behavior for the UB and ENG gradations, and a maximum enhancement was achieved for the engineered gradation specimens stabilized with the smaller aperture geogrid.

Repeated Load Triaxial Testing of Frozen and Thawed Soils

1985 ◽  
Vol 8 (4) ◽  
pp. 166
Author(s):  
VP Drnevich ◽  
DM Cole ◽  
G Durell ◽  
E Chamberlain
Keyword(s):  
Triaxial Testing ◽  
Repeated Load ◽  
Repeated Load Triaxial

Using Repeated-Load Triaxial Tests to Evaluate Plastic Strain Potentials in Subgrade Soils

2005 ◽  
Vol 1913 (1) ◽  
pp. 86-98 ◽  
Author(s):  
Anand J. Puppala ◽  
Suppakit Chomtid ◽  
Venkat Bhadriraju
Keyword(s):  
Plastic Strain ◽  
Test Procedure ◽  
Soil Layer ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Plastic Strains ◽  
Plastic Deformations ◽  
Subgrade Soils ◽  
Repeated Load ◽  
Repeated Load Triaxial

The design and the analysis of flexible pavement systems depend on soil layer characterization, traffic loads, and number of passes. The current AASHTO design method for flexible pavements uses resilient characteristics of subsoils to characterize and determine the structural support of each layer and to design the thickness of the layers. This moduli property, however, does not fully account for the plastic strain or rutting potentials of subsoils, as in the cases in which silt and mixed soils undergo high plastic deformations but possess high resilient properties. A study was initiated to establish a test procedure to use a repeated load triaxial device to measure plastic strain potentials of subgrade soils. Laboratory-compacted soil specimens were subjected to a repeated deviatoric load, determined as a percentage of static deviatoric load at failure under un-consolidated undrained conditions. The plastic strains were monitored during 10,000 repeated load cycles, and the accumulated plastic deformations were determined. The test procedure and test results conducted on two types of soils, a coarse sand and silty sand, are presented. Effects of soil type, compaction moisture content, dry unit weight, confining pressure, and deviatoric stresses on the plastic strains were addressed.

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