This study investigated the effects of freeze-thaw (f/t) cycles on the static and dynamic behaviors of plain cement-soil (PCS) sample and basalt fiber reinforced cement-soil (BRCS), with a series of laboratory experiments like split Hopkinson pressure bar (SHPB), unconfined compression strength test (UCT), and ultrasonic pulse velocity testing. The results showed that the incorporation of basalt fibers improved the wave velocity, unconfined compression strength (UCS), and dynamic compression strength (DCS), absorption energy (W_S) of cement-soil sample with f/t cycle. The UCS/DCS strength degradation was serious for both BRCS and PCS samples with 1 and 3 f/t cycle, after which the strength decreased slowly. With the strain rate increased from 150 s⁻¹ to 190 s⁻¹, the strength growth of BRCS against PCS gradually slowed down. Under different f/t cycle conditions, both power relationship and exponential relationship fitted well with the experimental data of wave velocity and UCS/DCS for the DCS of samples, but the UCS seems to be only suitable for the power relationship. The incorporation of basalt fibers changed the energy absorption mode of the sample under impact load and there was a positive correlation between the DCS and W_S.

The natural soil will have a significant strength improvement when admixed with reactive magnesia (MgO) and subjected to CO₂ carbonation, which has been identified as an innovative and environment-friendly technique in the domain of soil treatment. MgO activity has been revealed to have a significant influence on the treatment effectiveness during the carbonation process. With this in view, the effect of MgO activity index on physicochemical, electrical and strength properties of carbonated silt was investigated. Results show that the MgO activity index and initial water-MgO ratio play crucial roles in controlling the aforementioned properties. With the initial water-MgO ratio reducing or MgO activity index increasing, the mass increment ratio, growth rate of unit weight, pH, resistivity, strength and CO₂ sequestration increase to different degrees, while the volume increment ratio, water content, specific gravity, porosity and saturation degree decrease. The unconfined compressive strength shows a better linear relation with resistivity, indicating the applicability of resistivity method in the strength evaluation of carbonated MgO-admixed soil. Moreover, the thermal and microstructural analyses have explained the changing mechanism of physicochemical, electrical and strength properties. Finally, the analysis of the CO₂ sequestration indicates that the carbonated MgO-admixed silt could achieve a high carbonation degree when the initial water-MgO ratio is less than 2.0, showing the feasibility of MgO carbonation in the CO₂ sequestration.

The first underground research laboratory (URL) as the research platform for the deep geological disposal of high-level radioactive waste (HLW) in China is being built in a deep granite rock mass. The damaged characteristics and mechanical properties of the deep granite under loading seriously influence the URL’s construction safety and disposal function for HLW. Therefore, this paper investigates the damaged characteristics and mechanical properties of the Beishan deep granite used in various confining pressure levels through a series of triaxial compression and acoustic emission (AE) tests. Based on the crack volumetric strain model, the crack stress thresholds of the deep granite specimens under various confining pressure levels were acquired. The damage development of the specimens used in five confining pressure conditions was analyzed, and the evolution of AE parameters and strain energy of the deep rock under different damage stages were explored. The studied results shown that the crack stress thresholds of the deep granite rose linearly with the increasing confining pressure, but their stress ratios remained relatively constant under various confining pressure levels. Under the rock loading tests, the designed confining pressure levels influenced the AE hit count and AE accumulative count development under the rock damage process. The high-frequency points of the AE hit count coincide with the AE accumulative count increasing, and the maximum value of the AE hit count of the specimens used in different confining pressure conditions appears in the postpeak stress‒strain stage. Additionally, with the axial strain of the loading rock rising in the prepeak stress‒strain stage, all the strain energy (including total energy U, elastic energy U_e and dissipated energy U_d) continues to rise, and in the postpeak stress‒strain stage, U_e stored inside the rock is quickly released, resulting in the U_e/U decreasing and U_d/U increasing.

When pervious concrete is used as pile material, both high strength and water permeability will be available. By comparing the strength and permeability of pervious concrete with different aggregate size (3–5 mm and 4–6 mm) and porosity (20%, 25%, 30% and 35%), the recommended aggregate size (3–5 mm) and porosity (30%) can be achieved. To investigate the installation effect and bearing characteristics of the pervious concrete pile composite foundation, the excess pore water pressure, settlement, pile-soil stress ratio and skin friction were recorded in the model test. Results show that, compared with the impervious pile, the pervious pile can significantly accelerate the dissipation of excess pore water pressure after pile installation, and in the loading test can shorten the consolidation time by 30.3%, increase the skin friction 0.12 kPa averagely, reduce the peak value of excess pore water pressure by 30.2%, and increase the characteristic value of bearing capacity by 43.2%. When the linear penalty method is applied, and the friction coefficient is 0.6, compared with the test, the deviation of simulated skin friction is the largest, being about 15%, so in general the model test results are reliable.

En tr The collapsibility of loess has a great influence on subgrade construction in Qinghai, China, so laboratory tests are utilized to evaluate the collapsibility influencing factors, which illustrates that the collapsibility of this region is not dominated by soluble salts but an alkaline environment, high porosity and a low water content. The in situ self-weight submerging test reveals the settlement regularities, with a maximum settlement of 22.4 cm, which suggests that the soil in the test region is self-weight collapsible loess. In consideration of the economy and applicability, dynamic compaction was chosen as the ground improvement method. The optimal number of drops (N) for an energy level of 1000 kN·m is 6, and for the energy levels of 1500 kN·m and 2000 kN·m, N is 8. Besides the maximum effective depth for 1000 kN·m is 5 – 6 m, and it is 6 – 7 m for 1500 kN·m and 2000 kN·m. The collapsibility of loess has a great influence on subgrade construction in Qinghai, China, so laboratory tests are utilized to evaluate the collapsibility influencing factors, which illustrates that the collapsibility of this region is not dominated by soluble salts but an alkaline environment, high porosity and a low water content. The in situ self-weight submerging test reveals the settlement regularities, with a maximum settlement of 22.4 cm, which suggests that the soil in the test region is self-weight collapsible loess. In consideration of the economy and applicability, dynamic compaction was chosen as the ground improvement method. The optimal number of drops (N) for an energy level of 1000 kN·m is 6, and for the energy levels of 1500 kN·m and 2000 kN·m, N is 8. Besides the maximum effective depth for 1000 kN·m is 5 – 6 m, and it is 6 – 7 m for 1500 kN·m and 2000 kN·m.