Abstract:

In order to solve the problem of train speed limitation induced by track bed heaving in the entrance section of GZ Tunnel, the causes for heaving disease of track bed are explored by using manual monitoring method and supplementary exploration, and corresponding countermeasures are proposed. The deformation of track bed before and after the treatment on track bed heaving is observed by manual and automonitoring, and the effects of the treatment on the track bed heaving are evaluated. The results show that: (1) The main external causes of the track bed heaving are considered to be the combined working conditions of shallowburied depth, unsymmetrical pressure and uneven bearing capacity at the entrance section of the tunnel; the tunnelinginduced unsymmetrical pressure of the stratum is not fully adjusted, and the compression of unsymmetrical pressure on tunnel bottom structure causes the heaving of crosssection of track bed. (2) Considering the main factors such as the uneven foundation of the opencut tunnel section and the shallowburied depth and unsymmetrical pressure of the tunnel entrance, etc., some countermeasures such as the grouting of the ear wall bottom of the opencut tunnel, anchoring piles outside the tunnel, and rockbolt reinforcement of the track bed are proposed to prevent the track bed heaving. (3) The automonitoring results show that the heaving rate of the monitoring points No. L6 to L8, L10 and L11 at K1966+310.0 ~ +322.5 ranges from 1.38 mm to 3.70 mm per month before the treatment, and that of the monitoring points No. L6 to L8 and L10 ranges from 0.53 mm to 0.69 mm per month from Feb. 15th to Sep. 7th, 2018 after the treatment; and the heaving rate is reduced by 56.6% to 85.1%. However, no further heaving is found at the monitoring point No. L11 from May 13rd to Sep. 7th, 2018. (4) The manual monitoring results show that the monitoring points at K1966+300 ~ +340 heave slowly and some monitoring points show small settlement, except for the obvious heaving of the monitoring points No. B2 at K1966+320.0 and K1966+325.0 from Mar. 22nd to Sep. 7th, 2018. (5) According to the current monitoring results, preliminary analysis shows that the target of track bed heaving treatment in the entrance section of GZ Tunnel has not been fully achieved, the monitoring of track bed deformation is still continuing, and the treatment effect should be monitored and analyzed continuously.

Key words: passengerdedicated railway, tunnel entrance, track bed heaving, disease treatment, shallowburied unsymmetricallypressured tunnel, anchoring pile, rockbolt reinforcement, automonitoring, manual monitoring