MxV Rail conducted multiple single tie push tests (STPTs) between 2020 and 2023 to assess the changes in lateral tie resistance from tonnage accumulation, dynamic track stabilizers (DTS), tie type and ballast condition. High lateral tie resistance is necessary for preventing lateral misalignments and track buckles. Therefore, understanding how various factors affect the lateral tie resistance will aid in the development of track buckling risk assessments and ballast maintenance best practices.

The test involved tamping a section of track that consisted of both concrete and wood ties and then increasing the lateral tie resistance, using either tonnage during speed restrictions or a DTS. The STPTs and top-of-rail (TOR) elevation measurements were taken at multiple stages, including immediately after tamping and then after different tonnage increments or DTS. The results from this test were then added to a compiled measurement from previous tests, and the results from all the tests were used to develop general guidelines for ballast maintenance best practices and trade-off considerations.

The results showed multiple factors affect the lateral track strength and therefore the susceptibility to misalignments and track buckles. The disturbance from ballast tamping can reduce the lateral track strength by 20-80% (~45% median) and can be compacted from either tonnage (25-50% regain in strength after 0.1 m gross ton or MGT) or DTS (33-78% regain in strength). The amount of ballast (shoulder width and crib height), tie type and ballast characteristics all have a meaningful role in lateral track strength.

This paper is based on the testing programs conducted by authors at MxV Rail.