## 6 Discussion
Calculated from the data in Table 6, the gauge expansion of TLVT reaches the static management value when the axle load is 31.4t; the gauge expansion of ILVT reaches the static management value when the axle load is 35.2t. The comparison shows that ILVT track has better geometrical position retention capability than TLVT when running a 40t axle load train, and it can be better adapted to the operation of larger axle load trains in terms of geometrical position. According to the stress cloud diagrams of the two LVT structures (Figures 27-30), it can be seen that great tensile stress was observed at approximately one-third of the bottom surface of the TLVT bearing block, whereas the maximum tensile stress on the bottom surface of the ILVT bearing block appears at the center under the action of vertical load. The maximum tensile stress position on the bottom surface of the bearing block is near the edge of the track bed under the action of lateral and vertical coupled loads. The stress of the track bed slab mainly appears at the corner points of the bearing block, this implies that the unfavorable position of the TLVT track bed slab is mainly at the corner surface of the bearing block, and that of the ILVT track bed slab appears at the corner of the bearing block downward from the surface of the track bed slab that extends to the bottom of the groove and the short side of the end of the track slab. Therefore, these positions should be the focus of LVT structure optimization at 40t. It can also be seen that although the two structures are similar, their force characteristics are significantly different. Under the vertical load of 40t axle load, the stress at the bottom of the supporting block at the point of load application reaches the ultimate tensile strength of concrete. At the point of load 11, the stresses at T1, T2, T3, and T4 of TLVT reach 89%, 82%, 56%, and 90% of the ultimate tensile strength of concrete, respectively, the stresses at T1, T2, T3, and T4 of ILVT reach 77%, 62%, 62%, and 99% of the ultimate tensile strength of concrete, respectively. Under the lateral and vertical coupled load of 40t axle load, the stress at the bottom of the supporting block at the load application point of the two track structures exceeded the ultimate tensile strength of concrete, with TLVT exceeding 15% and ILVT exceeding 14%. At No. 8 load point, the maximum stress of TLVT and ILVT track bed slabs reached 94% and 93% of the ultimate tensile strength of concrete, respectively. At the load point of No. 11, the track bed slab stress is the largest at the T1 position, TLVT exceeds the ultimate tensile strength of concrete by 14%, and ILVT reaches 98% of the ultimate tensile strength of concrete. T3 is also the weak position of the track bed slab, and the stresses at TLVT and ILVTT3 reach 81% and 77% of the ultimate tensile strength of concrete, respectively. The above-mentioned scenes all show that ILVT has a better structure, which can further delay the cracking of the structure. Under the lateral and vertical design loads of the 30t and 35t heavy-haul train for the two types of track structures, the maximum stress of the track bed slab and the bearing block are within the ultimate tensile strength of the concrete. However, under the lateral and vertical design loads of the 40t axle heavy-haul train, the maximum stress of the TLVT track bed slab exceeds the ultimate tensile strength of concrete, with a stress on the bottom surface of the bearing blocks of the two track structures of 3.5 MPa. Therefore, the following methods are advised to optimize the design of the track structure to better application to the operation of 40t axle heavy-haul train:  
1. By lengthening the track bed by 50 mm and above, the maximum stress of the track bed can be reduced. 2. By increasing the concrete grade of the track bed slab to C50 concrete, the mechanical performance of the track bed slab can be improved. 3. By adopting C60 concrete and arranging steel bars at the bottom, the stress performance of LVT can be improved.