Alluvial silt is widely distributed in the Yellow River basin, especially in its largest alluvial plain, the Yellow River delta. In this area, owing to the wet and soft characteristics of the alluvial silt, cumulative settlement often occurs under traffic loads. To reduce the settlement, various methods are applied to improve the subgrade bearing capacity in this area. Among them, the use of calcium oxide (burnt lime) to treat shallow subsoil is a common selection. However, the effect and mechanism of this method have not been fully determined. Therefore, a large integrated device was developed for an in situ test so that the comparative analysis of the short-term settlement of the natural and burnt-lime-treated ground under traffic loads can be achieved. For the long-term cumulative settlement, a numerical method using a cumulative deformation model was applied to analyze the settlements after 10 years. Furthermore, the numerical method respectively predicted the settlement after 1 and 2 years to compare with the in situ test. The in situ test results demonstrate that the wave impedance of the alluvial silt subsoil treated with burnt lime grows and both the dynamic stress caused by wheel load and the excess pore water pressure are reduced. These indicated that the short-term cumulative settlement was significantly reduced after the alluvial silt subsoil was treated with burnt lime. Moreover, the results obtained by the numerical method are similar to those in the in situ test. For the long-term cumulative settlement, the calculation results of the numerical method indicated that the use of burnt lime to treat the ground is effective. In detail, 10 years later, the settlement of the burnt-lime-treated ground decreased by about 1/5.
This special issue of the International Journal of Geomechanics contains 10 papers that cover numerical and experimental investigations on various aspects of sustainable civil infrastructures. The topics include the self-healing capability of asphalt, cracking and fracture of asphalt pavement and portland cement concrete, soilimprovement techniques (including compaction and vertical drains), and various foundation systems. There are two papers on asphalt. The self-healing of asphalt mixtures can extend the fatigue life of asphalt pavement. Huang et al. developed a method based on fuzzy evaluation and the analytic hierarchy process for evaluating the self-healing capability of asphalt mixtures. The feasibility and effectiveness of the method were validated by a case study. To understand the mechanisms of material failure is essential for the design and construction of sustainable civil infrastructures. Chen et al. proposed a multiscale numerical modeling approach to analyze the distress of asphalt pavement on steel bridge decks and applied the approach to a case study. Their results highlighted the importance of bridge structure and pavement evenness in the distribution of pavement cracks. One paper focuses on concrete fracture and damage. Xu et al. investigated the spallation failure of fiber-reinforced concrete slabs under impact loading. Their numerical simulations showed that fibers can remarkably improve the tensile strength of concrete slabs and effectively limit the initiation and propagation of cracks. Soil improvement is an important element of sustainable civil infrastructures. Three papers are related to soil-improvement techniques, including compaction and vertical drains. Nie et al. presented an integrated theoretical and case study on anomalous data detection for roller-integrated compactionmeasurement. Their results showed that the proposed bidimensional anomalous data-identification method rendered a more accurate correlation, whereas the proposed neighbor-weighted estimation method improved the precision of compaction evaluation. Two papers are related to vertical drains. Azari et al. applied an elastic–viscoplastic model to model soft soil improved with vertical drains and compared their simulation results with field measurements. Their results showed that the distribution of the overconsolidation ratios in the disturbed zone greatly influenced the viscoplastic strain rates, creep strain limits, and consolidation. Parsa-Pajouh et al. evaluated the efficiency of several proposed formulations for plane-strain modeling of vertical drain-assisted consolidation through an integrated numerical and experimental investigation. By comparing the predicted and measured pore pressures in well-controlled laboratory tests, the advantages and disadvantages of these formulations were discussed. The remaining four papers deal with foundation systems. A better understanding of soil–structure interaction can lead to optimized foundation design and construction, which increase the sustainability of many civil infrastructures. Zhou and Dai presented a new strut-and-tie model for the analysis of force distribution among piles, pile caps, and superstructure components, including struts and ties. Through two case studies, they demonstrated the effectiveness and accuracy of their model. Farouk and Farouk examined the effect of a superstructure’s rigidity on the contact stress and differential settlement for plane two-bay frames. They found that the rigidities of walls and slabs have significant effects on the resultant average contact stresses and the maximum settlements under the footings, which affect the differential settlements. They provided new charts and equations for calculating the average contact stress and maximum settlements under the inner and outer footings for plane two-bay frames. Zhang et al. developed a numerical model to investigate the working mechanism of pervious concrete piles. Their model was validated by a case study. Their results showed that pervious concrete piles can reduce foundation settlement caused by their high stiffness and permeability and, hence, are particularly suitable for reinforcing foundations with low bearing capacity and soils with poor permeability. Yang et al. conducted a numerical investigation on the load-displacement behavior of a reinforced strip footing using a double-yield model. The effects of various parameters, such as burial depth, reinforcement length, and arrangement of two reinforcement layers, were studied. Their results showed that the load-displacement behavior of strip footings simulated with the double-yield model is more realistic than that with the Mohr-Coulomb model, and the optimal burial depth and length of reinforcement obtained from their study agreed well with values reported by previous investigators.
As a permeable base material of pavement, the large stone porous asphalt mixture (LSPM) is used widely in China to lessen the moisture damage of the asphalt pavement. However, the dynamics mechanism of the inhibitory effect of permeable base on moisture damage is not clear yet. The dynamic fluid-solid coupling analysis of the saturated pavement with LSPM base course, considering the asphalt mixtures as the porous medium, was performed using the finite difference numerical code FLAC3D. Numerical results revealed that the positive and negative dynamic pore pressure alternated in the pavement with the approaching and leaving of the wheel loads. The phenomenon of water pumping out of and sucking into the pavement under the moving loads was proved. The flow of fluid in pavement can be regarded as the laminar flow. The presence of the LSPM base course greatly decreased the dynamic pore pressure and the scouring force in the surface course because of the large permeability coefficient of the LSPM. The location of the maximum dynamic pore pressure also changed due to the LSPM base course. Due to the permeable base, the dissipation of the dynamic pore pressure was accelerated and thus the moisture damage was lessened.
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