Influence of impact forces on the strength characteristics of the railway roadbed

Abstract

The article presents the results of studies on the influence of impact forces on the strength characteristics of the soil of the main site of the roadbed (MSRB). It is shown that impulsive shock forces of 360 ... 530 kN, which initiate high-level accelerations in the ballast layer and on the main pad of the subgrade, arise in the presence of defects in the form of sliders and welds with oversized sizes on the rolling surface. When freight cars and locomotives running with speeds v = 50 ... 60 km/h, the levels of vibro-displacement on the main site of the roadbed are in the range of 50 ... 60 μm, but due to the impact of wheels with oversized defects, the values of vibro-displacement are reached at 220 ... 370 μm. The process of changing accelerations and vibro-displacements in the ballast layer and on the main site of the roadbed has an impulse short-term nature. The article analyzes the calculated limiting stresses from the action of the shock forces of interaction between wheels and rails performed using the theory of limiting equilibrium on an embankment of H = 2 m height, composed of clay soils, which showed that vibration levels with amplitudes of more than 300 μm on weak clay bases or waterlogged soils lead to a reduction of the stress limits on the FPRP by 1.6 ... 1.7 times. Increasing the humidity of clayey soils under impact loads is an important factor in reducing the values of ultimate stresses:- for clays with an increase in the yield index to 0.5 at an amplitude of vibrations of 300 μm, the ultimate stresses are reduced by 1.1 ... 1.28 times, with an increase in the yield index to 0.75 in 1.5 ... 1.96 times;- for loams with an increase in the yield index to 0.5 in 1.16 ... 1.21 times, with an in-crease in the yield coefficient to 0.75 in 1.58 ... 1.6 times.Operation of the rolling stock with oversized defects on the rolling surface of the wheels can lead to micro-shifts in the ground space, the accumulation of deformations and defects in the roadbed.

Keywords

• impact forces
• vibration displacements
• limit equilibrium
• slip lines
• stresses
• clay soils