Frost resistance is a very important durability criterion of concrete in the cold environment. To improve the frost resistance of concrete, carbon fiber was added into the concrete. Repeated soaking in water will accelerate the freeze-thaw damage of concrete, resulting in mass loss and the compressive strength decrease of the concrete. Thus, a recurrent freeze-thaw experiment, in which specimens of carbon-fiber-reinforced concrete were frozen for 4 h and then thawed in the warm water for 4h, was carried out to estimate the relationship of the addition of carbon fiber and frost resistance. The results show that adding the carbon fiber into concrete could reduce the mass loss of the concrete during the freeze-thaw experiment. And when the carbon fiber content is more than 0.50 wt.‰, the increase in the carbon fiber content improved the compressive strength of the concrete significantly. The frost-resistance of the plain concrete is 100 freeze–thaw cycles, after which the compressive strength losses were 21.2% and 9.0%, respectively. When the optimal adding amount of carbon is 1.5 wt.%, the frost-resistance of the concrete is 250 cycles. It indicates that the carbon-fiber-reinforced concrete is suitable for buildings in cold and moist conditions.

To investigate the influence of addition amount and length of steel fibers on the bearing capacity of a concrete beam, this study simulated the crack propagation process of a concrete beam in a four-point bending experiment. The extended finite element method (XFEM) using the ABAQUS software was adopted. Additionally, stress distribution trends for the concrete under loading and load–displacement curves at the stressed points were obtained. The simulation results for a concrete beam with different amounts and lengths of steel fibers were compared and analyzed, and conclusions were drawn. The experiment shows that the flexural performance of the concrete improves with increases in the length and amount of steel fibers, but the reinforcement effects produced by different amounts and lengths of steel fibers are different. When the steel fiber content is 1.5% and the length is 20–25 mm, the reinforcement effect in the concrete is significantly improved, and its flexural strength is nearly doubled.

Recently, with the development of geophysical exploration technology, geophysical engineering instruments and methods have also improved. The multi-electrode resistivity method is widely used in engineering exploration. In this paper, multi-electrode resistivity tests were carried out in a seasonal frozen soil area in Heilongjiang Province, to provide an optimized multi-electrode resistivity method under the conditions of frozen soil. Combined with shear wave velocity tests and standard penetration tests, multi-electrode resistivity tests were used to comprehensively analyze and evaluate the physical and mechanical properties of Tertiary semi-diagenesis rocks. The results show that the high resistivity due to the frozen surface layer acting as a shield can be eliminated by technical means. It is feasible to test the resistivity through the frozen surface layer. The multi-electrode resistivity method can visually reflect the interface between saturated sand and semi-diagenetic rocks. Dividing the interface between saturated sand and semi-diagenetic rocks is advantageous as the morphology of the resistivity curve has a significant curvature change. There is a strong correlation between the resistance and shear wave velocity of a strata in which the Pearson correlation coefficient is as high as 0.99. The multi-electrode resistivity method test used in combination with the shear wave velocity test and the standard penetration test could give the bearing capacity and frictional resistance of semi-diagenetic rocks, which saves a lot of time and material costs in engineering exploration.

Drilling has been conducted to investigate the petrogeochemistry of the Late Pleistocene Guxiangtun Formation and Holocene Wenquanhe Formation in Northeast China. Both Guxiangtun and Wenquanhe Formations are fluvial facies, which are composed mainly of quartz and feldspar, with minor mica and clay minerals. To understand the provenance and tectonic setting of these sediments, geochemical analyses of fifteen selected samples from the drill core have been carried out. Compared to the composition of the upper continental crust (UCC), the sediments exhibit higher SiO₂, similar TiO₂ and K₂O, and lower Fe₂O₃, MgO, MnO, CaO, and Na₂O contents. The bivariant plot of Th/Sc versus Zr/Sc ratios indicates the contribution from recycled sedimentary provenance for our studied sediments; furthermore, the low to medium degree of weathering of these sediments is commonly indicated by the chemical index of alteration (CIA) of 52. The discriminant function diagram using major elements shows a mixed provenance of the sediments, including quartzose sedimentary and felsic igneous rocks. According to the Fe₂O₃+MgO vs. K₂O/Na₂O plot and Th–Sc–Zr/10 diagram, the sediments under the investigation fall mostly within the active continent margin field.