Laboratory study on subgrade fluidization under undrained cyclic triaxial loading

Abstract

A long term issue that has hampered the efficient operation of heavy haul tracks is the migration of fluidized fines from the shallow soft subgrade to the overlying ballast, i.e., mud pumping. This paper presents a series of undrained cyclic triaxial tests, where realistic cyclic loading conditions were simulated at low confining pressure that is typical of shallow subgrade beneath a ballast track. Subgrade soil specimens with a low plasticity index collected from a field site with recent history of mud pumping were tested at frequencies from 1.0 to 5.0 Hz and a cyclic stress ratio (CSR) from 0.1 to 1.0. The experimental results indicate that under adverse loading conditions of critical cyclic stress ratio (CSRc) and frequency, there is upward migration of moisture and the finest particles towards the specimen top, and this causes the uppermost part of the soil specimen to soften and fluidize. Conversely, a smaller value of CSR tends to maintain stability of the specimen despite the increasing number of loading cycles. It is noteworthy that for any given combination of CSR and frequency, the relative compaction has a significant influence on the cyclic behaviour of the soil and its potential for fluidization.

The mechanism and effects of subgrade fluidisation under ballasted railway tracks

“…These limits are collectively known as the Atterberg limits. The subgrade soils that were reported to have already pumped are mainly in the low-to-medium plasticity region on the soil plasticity chart [5,12]. However, several of the mud pumping locations in New South Wales, Australia, are along the east coast, so they consist of low compressible estuarine clays with water levels that are often close to the liquid limit [5].…”

Mechanistic Mathematical Modelling of Pothole Development from Loss of Roadway Subsurface-Materials

“…(2f). 18) We adapted C2 = the number of materials lost but trapped in the top part of the stone base and not deposited on the pavement's surface, and its formula is from the study [20]. Eq.…”

“…Using those assumptions may not describe what happens below the surface layers. Research show that for potholes to occur on a roadway, water pressure and traffic-load should be present [2,12,13,[18][19][20]. Their presence leads to a rise in pore-water pressure.…”

“…Studies have shown that modeling the movement of particles upwards consider several principles [1,2,7,12,18,[20][21][22][23][24][25][26][27]. The principles examined were mud-pumping, advection, internal-erosion, solute transport, pore-water pressure, suction, suffusion, pore fluid viscosity, and roadwaymaterials breakdowns under both traffic-loads and water movement.…”

“…Several researchers have studied the phenomenon that involves the pumping out, migration, or movement of particles from the road's subsurface upwards [1,4,18,19,20,22,23,[25][26][27][28]. Most of these researches did not relate their findings directly to pothole development's engineering problem on roads.…”