The relationship between moisture transportation and efflorescence in sodium hydroxide- or sodium silicate-activated fly ash/slag geopolymers was investigated. The results show that the efflorescence products are sodium carbonate hydrates, mainly composed of natron, heptahydrate, trona and sodium carbonate. The efflorescence induces compressive strength loss, water absorption increases and pore structure degradation in the geopolymer. When the curved surface of a geopolymer cylinder is covered with plastic film, the moisture transportation drives the free alkalis to the top surface to initiate efflorescence. In comparison, the efflorescence occurring on the curved surface of an uncovered geopolymer cylinder results in a more intensive alkalinity loss. For the uncovered geopolymers prepared with sodium hydroxide activator, efflorescence deposits are formed on the lower half of cylinder. A low capillary absorption capacity developed in the pore structure can only drive the moisture to the middle of cylinder, which is confronted with the drying front. More efflorescence products are formed on the upper half of the uncovered geopolymer cylinder prepared with sodium silicate activator. A relatively higher capillary absorption capacity, developed in the more compact pore structure, transports the moisture from the bottom to the top of cylinder, so no drying line is observed in the cylinder.

Despite many cases of textile-reinforced engineered cementitious composites (TR-ECCs) for repairing and strengthening concrete structures in the literature, research on lightweight engineered cementitious composites (LECC) combined with large rupture strain (LRS) textile and the effect of textile arrangement on tensile properties is still lacking. Therefore, this paper develops textile-reinforced lightweight engineered cementitious composites (TR-LECCs) with high strain characteristics through reinforcement ratio, arrangement form, and textile type. The study revealed that, by combining an LRS polypropylene (PP) textile and LECC, TR-LECCs with an ultimate strain of more than 8.0% (3–4 times that of traditional TR-ECCs) could be developed, and the PP textile’s utilization rate seemed insensitive to the enhancement rate. The basalt fiber-reinforced polymer (BFRP) textile without epoxy resin coating had no noticeable reinforcement effect because of bond slip; in contrast, the BFRP grid with epoxy resin coating had an apparent improvement in bond performance with the matrix and a better reinforcement effect. The finite element method (FEM) verified that a concentrated arrangement increased the stress concentration in the TR-LECC, as well as the stress value. In contrast, a multilayer arrangement enabled uniform distribution of the stress value and revealed that the weft yarn could help the warp yarn to bear additional tensile loads.

The stability of dam foundations at great depth has always been a challenging problem concerned by designers. This study built a three-dimensional numerical model of the dam and foundation under a complex geological condition in the project area of the Chinese Kala hydropower station. The numerical model was imported into the finite difference software FLAC3D to conduct a numerical simulation. Overload and strength reduction methods were adopted to evaluate the stability of the dam foundation at great depth. The results indicated that the structural faults had an essential impact on the stability of the dam foundation. The stability analysis showed that the safety factor of the dam foundation is greater than 2.5, which met the standard’s requirements. The simulation results can provide a reference for the design and engineering reinforcement of the Kala dam foundation.

In this study, a numerical model of the conglomerate reservoir is established using ABAQUS. Cohesive elements are embedded into the numerical model to simulate the hydraulic fracturing behaviours of the conglomerate reservoir. The cohesive elements split by the high-pressure liquid flow are identified by tracing the crack propagation. A USDFLD (user-defined field variable) subroutine is used to increase the liquid flow’s dynamic viscosity in these cracked cohesive elements. Using this method, ABAQUS successfully simulates the temporary plugging-refracturing processes in the conglomerate reservoir under four in-situ stress states. This study found that with the increase of the horizontal in-situ stress difference, the pore pressure at the fluid injection point increased correspondingly. Under the conditions of higher horizontal in-situ stress differences, more complex branch fractures were generated in the conglomerate reservoir.

Machine learning models have been increasingly popular in landslide susceptibility mapping based on the correlations among landslides and their inducing factors. However, mislabeled data in model training sets would deteriorate model accuracy. This study employed a Bayesian network to analyze influencing factors on landslides in Fujian Province, China, prone to typhoons and landslides. An inventory of 5,992 historical landslides informs Bayesian network modeling, with ten geoenvironmental factors as predictors. We introduced a progressive noise filtering method to mitigate the mislabeling effects of non-landslide points. The results show that altitude, wind speed, and lithology are the most important factors of landslides in the study area. The accuracy of the resultant landslide susceptibility map was verified using the area under the receiver operating characteristic curve (AUC) and Moran’s I index. The AUC value was improved from 0.838 to 0.931 during the progressive noise filtering. The correlation between historical landslide number density (LND) and resultant landslide susceptibility index (LSI) was evaluated. The Local Indicators of Spatial Association based on Moran’s I index shows consistent distribution patterns for high LND and high LSI regions. This study provides a useful reference for reliable landslide susceptibility mapping in the study area and similar areas.