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The cold patch asphalt mixtures (CPAMs) have been manufactured by mixing the cold patch asphalt liquid (CPAL) with type LB-13 mineral mixture. The workability, Marshall stability, Freeze–thaw splitting strength and cohesion of three types of CPAMs were tested in the laboratory. The potholes were repaired using CPAMs on several sites in S101 provincial highway at Feidong. The CPAMs were sampled to measure the bulk density and Marshall stability, and the volume of air voids (VV) of those specimens was calculated. The results indicated that the Brookfield viscosity of CPAL affected the workability of the CPAMs. The Marshall stability of three types of CPAMs was only 3.07, 3.80 and 4.28 kN, respectively. However, the CPAMs had better water stability and met the requirements of hot mix asphalt (HMA) in low-rain regions referring to JTG F40-2004. The VV decreased and Marshall stability increased with the action of the secondary compaction and the volatilization of additives. Beyond 3 months, the Marshall stability of the compacted mixtures tends to be stable. The Marshall stability of type A and B CPAMs changed from 5 to 6 kN, while that of type C CPAM varied between 4 and 5 kN. The products met the requirements of dense-graded HMA on the low-grade highway. Overall, the prepared CPAMs can be used to repair pavement potholes from the perspective of material properties and molding intensity.

In this paper, the mechanical properties of micropowder cement mortar and engineered cementitious composites (ECC), using different processing municipal solid waste incineration (MSWI) as a mineral admixture, were investigated. Through the direct ball milling method, ball milling heat treatment method, water washing ball milling method and water washing heat treatment ball milling method, the mechanical properties of MSWI bottom slag-regenerated micropowder cement mortar were tested. Compared with other groups, the flexural strength and compressive strength of the specimen prepared by the MSWI after washing and heating (750 °C, 5 h) were the highest, which reached 82.0% and 81.0% of the reference group, respectively. Based on this treatment, a uniaxial tensile test, three-point bending test and single fiber pull-out test were then carried out to explore the relevant ECC properties containing MSWI. The strain-hardening index PSH of ECC was determined by analyzing the fracture toughness and elastic modulus, fiber/matrix interface chemical bond and friction bond strength of ECC containing MSWI. The results showed that the PSH index of ECC was higher when the treated powder content was 2.2, the w/c ratio was 0.25 and the fiber volume content was 2.0%. This led to higher tensile ductility, which made it easier to achieve stable multi-slit cracking and strain-hardening behavior.

We estimated the areas exhibiting high-frequency (1∼10 Hz) wave radiation on the fault plane of the 2008 Wenchuan earthquake, by applying envelope inversion to strong-motion acceleration records. The corrected records of two small earthquakes are adopted as the empirical Green’s functions. Considering the change in the rupture pattern of the Wenchuan earthquake from southwest to northeast, the records of small earthquakes dominated by thrust and strike-slip are utilized as the empirical Green’s function for the southwestern and northeastern fault sections, respectively. The results are as follows: (1) According to the high-frequency wave radiation, the rupture process is complex. High-frequency waves radiated strongly in six areas: around the initial rupture point, along the north and south edges of the fault plane, near the area of intersection with the cross-cutting Xiaoyudong fault, south of Nanba, and near the area of Qingchuan. In total, these areas can be divided into three cases. In the first situation, high-frequency waves radiated strongly around the initial rupture area, which may be associated with the initiation of rupture and a high stress drop. The second location is near the periphery of the fault, which is associated with the termination of rupture. The third condition comprises high-frequency waves near the intersection with the cross-cutting Xiaoyudong fault. This area as a geometric barrier, and the surface rupture is observed. (2) The distribution patterns of the high- and low-frequency radiation intensity differ on the fault plane. From the hypocenter to the point of intersection with the Xiaoyudong fault, the high-frequency wave is located around the area with large slip value. In other areas, the distribution of the high- and low-frequency radiation is no obvious relationship. This different characteristic indicates the complexity of the rupture process.

Three pavement structures, including fatigue-resistant layer sandwich structure (FRLSS), sandwich asphalt pavement structure (SAPS) and semi-rigid base pavement structure (SRBPS), were designed to investigate their adaptability to the differential deformation of highway embankment on black cotton soil (BCS), which shrink/swell behavior was modeled by the coupled consolidation theory for unsaturated soils. The maximum additional tensile stress in pavement was obtained, and the present serviceability index (PSI) and the international roughness index (IRI) were calculated by the vertical movement, pavement properties and traffic data. The adaptability of those pavement structures to the differential deformation of highway embankment was evaluated by grey relational analytical method using the PSI, IRI and additional tensile stress as the indexes. The results reveal that FRLSS presents the better effect in controlling cracks on the key-layer bottom, while SRBPS presents the better effect in controlling cracks on the pavement surface. The effect in controlling roughness decreases gradually from FRLSS, SAPS to SRBPS in order. The adaptability of FRLSS to the soil movement of highway embankment on BCS is superior to SAPS, which excels SRBPS. Overall, FRLSS should be given priority in designing asphalt pavement underlain by BCS foundation from the perspective of controlling roughness and cracks.

This research provides a method for introducing the broken rate of the coarse aggregates to optimize gradation of multi-supporting skeleton asphalt mixtures (MSSAM). The MSSAM was designed and then verified by comparing the measured volume parameters with designed criterion. Single Marshall tests were performed on single and multiple sized aggregates to find the boundary of coarse and fine aggregates. The tamping method replaced the Marshall compaction to measure accumulated density of the coarse aggregates. The broken rate of the coarse aggregates was introduced to optimize gradation of MSSAM. The wheel-tracking and low-temperature bending tests were finally performed to evaluate the pavement performances of the modified MSSAM. The results indicated that the gradation degeneration of MSSAM introduced by the crushed coarse aggregates resulted in the volume parameters to deviate from the designed criterion. The grain size of 4.75 was identified as the boundary of coarse and fine aggregates. Introduction of the broken rate of the coarse aggregates neutralized the gradation degeneration in the Marshall compaction, and brought the measured volume parameters nearer to the designed criterion. The modified MSSAM had a high dynamic stability and met requirements of low-temperature performance at minus 9 °C, was a good choice for the southeast China with heavy traffic.

This research revealed the crack generation of the highway embankment from the water losing shrinkage of the wet black cotton soil (BCS), which is a type of soil with high swell-shrink potential. The road seepage meter was used to test the permeability of filling materials, which was used to replace BCS. The moisture content and embankment deflection of BCS foundation were measured after the rainy season. Based on the coupled consolidation theory for unsaturated soil, the change in additional tension stress of the embankment induced by water loss shrinkage of BCS was simulated by Abaqus. The results indicated that the rainfall seeped into the foundation through highly permeable refill materials to result in BCS expansion and decrease the embankment strength. After the rainy season, the additional tensile stress caused by water loss shrinkage of BCS induces cracking of highway embankment, and the maximum cracking depth often appears at the shoulder of highway. The deep and wide cracks are easy to appear in the low embankment constructed on a thick BCS foundation under strong evaporation.

Black cotton soils (BCSs) were stabilized with various percentage of lime, natural volcanic ash (VA) and their combinations. The laboratory tests were performed to evaluate the influence of the stabilizers on the physical-mechanical properties of BCS. These laboratory tests included Atterberg limits, California bearing ratio (CBR), swell percent and unconfined compressive strength (UCS). The changes of minerals were also derived by performing X-ray diffraction, Infrared spectroscopy and scanning electron microscope, which were employed to explain the stability mechanism of BCS together with pH test. Results revealed that the added stabilizers improved greatly the physical-mechanical properties of BCS. The use of combinations of lime and VA showed superior results when compared with the single stabilizer. BCS can meet the performance requirements of roadbed materials referring to JTG D30-2015 just by mixing with 3% lime and 15% VA. The increased pH of the stabilized BCS indicated that solubility of the silicate and the aluminate increased, which accelerated the pozzolanic reaction between clay soils and stabilizers. The intrinsic lamellar structures of clay mineral were destructed in the reaction process. Moreover, several new minerals were produced to stabilize the soil fabric. Overall, the use of VA can reduce the consumption of lime in BCS stabilization and actualize the utilization of vast resources BCS as a low-cost roadbed material.

In the reuse stage of a gob-side entry retaining, failure of the structure and stability of the main roof have a significant effect on the safety of the advanced support and ventilation space at the working face. In this study, field investigation, theoretical analysis, and industrial experimentation were performed to analyse the fracture characteristics and formation process of the gob-side entry retaining roof during the reuse period. A dynamic-equilibrium mechanical model of the main roof structure is presented and the formation mechanisms of different types of short cantilever rock beam structures are clarified. The following major conclusions are drawn: (1) Three types of short cantilever rock beam structures occur in the main roof of a gob-side entry retaining during the reuse period, namely, the “short cantilever-articulated rock beam” structure, “short cantilever step rock beam (type I)” structure, and “short cantilever step rock beam (type II)” structure. (2) The stability criterion for these three short cantilever rock beam structures was also determined; that is, when the sliding instability coefficient K ≥ 1, the short cantilever-articulated rock beam structure will form, and when the sliding instability coefficient K

To evaluate the generation method of a digital asphalt-mixture specimen based on the discrete-element method, an algorithm for generating three-dimensional coarse aggregates is presented in this study. The simulation result shows that this algorithm can reflect the actual geometry (e.g., shape, size, fracture surface, and angularity) of aggregate particles. The digital three-dimensional specimen generated using this algorithm can model the three-phase system of coarse aggregates, air voids, and asphalt mastic for asphalt mixtures well. To estimate the distribution of coarse aggregates, both in the digital specimen and real asphalt mixture, the position and quantity of the coarse aggregates within a two-dimensional section of the asphalt mixture were adopted as evaluation indices. The results showed that the digital asphalt-mixture specimen was in good agreement with the real asphalt mixture, and the evaluation indices could be used to quantitatively analyze whether the digital specimen could reflect the real asphalt mixture. The proposed approach based on the discrete-element method can be used as a supplemental tool to evaluate the uniformity of asphalt mixtures for micromechanical analysis.