Search Results (3)

The objective of this research is to solve the problem of the lack of prediction methods and basis for the long-term road performance of oil shale residue-modified soil in seasonally frozen regions. This paper summarizes and expands the resilient modulus prediction methods in the related literature. Based on the measured soil–water characteristic curve (SWCC) of the compacted modified soil and the trend characteristics of dynamic resilient modulus under freeze–thaw cycles, a semi-empirical prediction model is proposed. This model was used to quantitatively forecast the resilient modulus of unsaturated modified subgrade soil after the freeze–thaw cycle in a seasonal permafrost region. The applicability and accuracy of the method were verified by dynamic resilient modulus tests of the oil shale residue-modified soil under various freeze–thaw cycles and moisture content. The results show that the model has a high degree of fit to the experimental data and is more suitable for predicting the dynamic resilient modulus of modified soil under the change of moisture and the freeze–thaw cycle compared to the existing models. Full article

Frost heaving and boiling are the most common road disorders due to the special climatic conditions in a seasonal frozen area. From the perspective of controlling road disorders in seasonally frozen areas and making effective use of industrial waste residue, two kinds of subgrade modified soil—crumb rubber modified fly ash soil (CRFS) and oil shale waste residue modified fly ash soil (OSFS)—were proposed by the research group. The research results proved that the two new subgrade fillers both have excellent engineering characteristics in cold areas, such as high strength and low thermal conductivity, and both have the function of waste utilization, giving them broad application prospects. In road engineering, the instability of slopes and retaining walls and the uneven settlement of the subgrade are closely related to soil creep, which are problems that cannot be ignored in road design and use. As a new material to treat road disorders in seasonally frozen areas, more attention should be paid to the continuous deformation property of modified soil under long-term load. The study on the creep characteristics of the modified soil can provide reliable parameters for the design of the modified soil subgrade and predict the settlement of the subgrade after construction, which is of great significance to the stability of the subgrade. In this paper, an experimental study on the consolidation–creep characteristics of two kinds of subgrade modified soil in a seasonal frozen region was carried out, the relationship between modified soil deformation and time is discussed, and the effects of different moisture contents and compaction degrees on the creep characteristics of modified soil were analyzed. The test results provide parameters for the engineering design of modified soil subgrade and provide data support for the popularization and application of modified soil in seasonally frozen subgrade. Full article

In order to achieve the purpose of subgrade frost damage control and waste utilization, this paper proposes a specific kind of composite subgrade structure which is suitable for subgrade in seasonal frozen regions, especially wet subgrade. The composite subgrade structure is composed of extruded polystyrene (XPS) plates as a cold resistance layer and modified subgrade soil with excellent frost resistance which can consume a lot of oil shale residue and fly ash. To provide valuable reference for engineering applications, an outdoor model test is designed and carried out based on indoor test results and actual engineering data. The cold resistance performance of this new type subgrade structure is evaluated by comparing the temperature distribution, energy transfer, and freezing index of the composite subgrade and the common subgrade during the freezing process. The results show that, firstly, the cold resistance layer can effectively preserve temperature inside the subgrade and form a positive temperature zone beneath XPS plates, which can ensure that the subgrade soil in a certain range will not freeze during the freezing period. Secondly, the position with the best cold resistance effect of the cold resistance layer is directly under the XPS plate. In actual application, the key position should be covered as completely as possible by XPS plates to ensure the cold resistance effect. Thirdly, the cold resistance layer can not only protect subgrade soil under XPS plates from frost damage, but also raise and keep the service temperature of the structure above XPS plates in a certain range, which is beneficial to the cold resistance durability of the entire road. This means that the composite subgrade can greatly reduce the occurrence of subgrade frost damage, thereby even improving the service capability of roads in seasonal frozen regions. Full article