Gongcheng Kexue Yu Jishu/Advanced Engineering Science

The mechanical properties of the soil-structure interface have always been one of the key and hot issues in the field of geotechnical engineering, and revealing its mechanism is helpful to promote the understanding of the bearing characteristic of structures such as pile foundations and retaining walls. A total of 28 groups of large direct shear tests with the post-grouting sand–concrete interface were conducted under three different grout volumes and four kinds of loading and unloading conditions to analyze the interface mechanical properties and the distribution of shearing influence range. The test results show that grouting can gradually eliminate the difference between the interface’s initial shear modulus and shear stress due to the loading and unloading of the interface. The softening phenomenon doesn’t exist in the un-grouted interface, while the post-grouting interface exhibits softening and the softening occurs in the unloading interface shearing process with low applied normal stress. The grout cement improves the mechanical properties of the interface by increasing the equivalent cohesive force of the interface but has no significant effect on the equivalent internal friction angle of the interface. The improvement of the interface equivalent cohesive force on the loading interface is better than the unloading interface under the same grout volume. The distribution of interface shearing influence range under unloading conditions is slightly larger than that under the loading conditions. Regardless of the loading, unloading, and grouting conditions, the distribution of interface shearing influence range is positively correlated with the interface peak shear stress. Under the same applied normal stress, the mechanical properties of the unloading post-grouting interface were improved due to the formation of the grout bulb by compaction grouting to increase the roughness of the concrete plate, while the mechanical properties of the loading post-grouting interface were improved by penetration grouting to form the soil-cement mixture. The research results can provide guidance for the post-grouting of pile foundations in practical projects.

Sillenite bismuth ferrite (S-BFO) was prepared by a co-precipitation-low temperature hydrothermal technique. The catalytic performance of S-BFO was evaluated by activating peroxymonosulfate (PMS) to remove ciprofloxacin (CIP). The results showed that adding 0.675 mmol/L PMS and 1000 mg/L of catalyst at the condition of initial pH value (6.5±0.1) and reaction temperature (25±1)℃, the removal rate of CIP (5.0 mg/L) was reached 84.8%. Under the same reaction conditions, the degradation efficiency of S-BFO activated PMS for CIP was higher than persulfate (PS). The morphology and crystal structure of S-BFO were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The effects of PMS concentration and initial pH value on the degradation of CIP in S-BFO/PMS system were investigated. The application potential of S-BFO/PMS system in the treatment of pollutants under real water conditions was evaluated. The results of ROS quenching experiments indicated that 1O2 is the main ROS in the S-BFO/PMS system, rather than $\cdot \mathrm{SO}_4^{-} $ or ·OH. The mechanism of degradation of CIP in the S-BFO/PMS system was also proposed. Finally, the 9 main products and intermediates of CIP were analyzed using liquid chromatography tandem mass spectrometry (LC/MS/MS) technology, and two possible degradation pathways was proposed including hydroxyl addition reaction (Pathway Ⅰ) and decarboxylation reaction (Pathway Ⅱ). This study provides important theoretical support for advanced oxidation technology based on persulfate in the field of wastewater treatment.

The rapid development of new energy has brought opportunities and challenges to the electric power and chemical industry. On the one hand, the consumption of renewable energy leads to a large amount of waste of energy such as water and light. On the other hand, replacing carbon-based fossil energy ammonia with green hydrogen as raw material can greatly reduce the carbon emissions of the chemical industry. Therefore, the use of hydropower, photovoltaics, and other renewable energy sources to electrolyze water to produce hydrogen can provide green raw materials for ammonia synthesis, which can significantly improve the capacity of renewable energy consumption, reduce energy consumption, and carbon emissions, and serve the national goal of “carbon peaking and carbon neutrality”. However, the fluctuation of renewable energy power is difficult to meet the stability requirements of the traditional synthetic ammonia production process, and there are still many challenges in the design and operation of large-scale renewable energy electrolysis of water to produce hydrogen and synthetic ammonia. There is an urgent need to carry out systematic research and breakthroughs in key technologies for the integration and regulation of large-scale electrolysis of water for hydrogen production to ammonia synthesis systems that adapt to the fluctuating characteristics of renewable energy. In this regard, the process and its topology structure of the renewable energy electrolysis water and the synthesis ammonia process are firstly introduced, including the electrolysis water hydrogen production section, the compression buffer section, and the chemical ammonia synthesis section. Furthermore, the key technical system for the construction of the system was proposed, including the synthetic ammonia process multi-stable optimization and flexible control technology under the fluctuating conditions of renewable energy, the modular integration and cluster dynamic control technology for large-scale hydrogen production system by electrolytic water with “electricity–heat–mass” coupling, “source—grid—hydrogen—ammonia” system-wide coordinated control technology for the volatility of renewable energy and multi-stable characteristics of the chemical industry, comprehensive security protection and market operation for electricity, hydrogen, ammonia, and other elements mechanism. Contents include: Aiming at the optimization of the synthetic ammonia process and multi-stage cooperative regulation technology suitable for flexible production, a high-fidelity proxy model for synthetic ammonia is developed by integrating the subsystems of the synthetic tower, compressor, gas separation, and heat transfer network, considering the hydrogen storage and supply quantity and the performance of the catalyst. The adaptation scheme and collaborative control technology of each subsystem of water electrolysis for hydrogen production and ammonia synthesis under the fluctuation of renewable energy supply and market demand are studied. Aiming at the modular integration and cluster dynamic control technology of large-scale water electrolysis and hydrogen production system, the multi-time-scale time-domain simulation method of the cluster system is studied based on singular perturbation and surrogate model technology, and the multi-physical coupling state space model of the electrolytic cluster system is established. Considering the module startup-shutdown unit commitment scheduling, scheduling and power allocation between the modules, and safe operation of the interval constraint and electro-thermal interface features, to improve the hydrogen yield, improve energy efficiency, improve the power tracking and grid load frequency control as the goal, to build the multi-objective hierarchical cluster system scheduling and control model. Aiming at the whole system cooperative control technology of hydrogen energy participating in the power grid, the flexible operation method of multiple sections with steady-state operation characteristics of hydro-solar complementary power generation, power-to-hydrogen production, hydrogen storage, ammonia synthesis, and ammonia storage is studied, and the flexible dynamic cooperative control method of electric hydrogen production and ammonia synthesis system is also studied. The simulation model of electric hydrogen production and ammonia synthesis system with static equivalent and parameter aggregation methods is integrated. The optimal control method and technical index of the system with hydrogen and ammonia in the source grid are studied. Combined with the characteristics of frequency modulation and peak regulation, the strategy of power-to-hydrogen production and ammonia synthesis system participating in power system auxiliary service is studied. It has significant social benefits and strategic significance to improve the local consumption rate of renewable energy and the friendliness of grid-connected scheduling and reduce chemical carbon emissions and reduce chemical carbon emissions by building a large-scale water electrolysis system for hydrogen production and ammonia synthesis with renewable energy.

To solve the problems of low penetration, serious wear and low rock-breaking efficiency during traditional disc cutter rock breaking under the geological conditions of hard rock, many new auxiliary rock breaking methods have been proposed, such as creating pre-cutting grooves on the rock through laser, water jet, and other non-contact rock-breaking methods to assist disc cutter rock breaking. To clarify the rock breaking mechanism of the disc cutter under the condition of the pre-cutting grooves, the particle discrete element method is used to establish two auxiliary rock breaking simulation models for the pre-cutting grooves at the side of the disc cutter (side-type) and in front of the disc cutter (front-type). The influences of the depth of the pre-cutting grooves and the cutter spacing on the propagation of rock-breaking cracks by the disc cutter are explored. The research results show that: 1) The pre-cutting grooves in the side-type auxiliary rock-breaking model mainly affect the expansion of cracks, and the lateral cracks propagate to the bottom of the pre-cutting grooves during the process of inducing rock breaking. The pre-cutting grooves in the front-type auxiliary rock-breaking model mainly affect the initiation of cracks, and only lateral cracks are generated at the early stage of penetration, and the lateral cracks are promoted to propagate to both sides; 2) The vertical force of the disc cutter and the number of cracks decreases with the increase of the depth of the pre-cutting grooves, while the vertical force of the disc cutter increases with the increase of the cutter spacing, and the number of cracks first increases and then decrease with the increase of the cutter spacing; 3) Under the same condition, the side-type auxiliary rock-breaking model is higher than that of the front-type auxiliary rock-breaking model, but the vertical force of the disc cutter in the front-type auxiliary rock-breaking model is much smaller than the vertical force of the disc cutter in the side-type auxiliary rock-breaking model. The auxiliary effect of the pre-cutting grooves can be fully utilized by further increasing the penetration of the disc cutter in the front-type auxiliary rock-breaking model; 4) When the penetration of the disc cutter is constant, the side-type auxiliary rock-breaking model is suitable for the case where the depth of the pre-cutting grooves is greater than the penetration of the disc cutter, and the front-type auxiliary rock-breaking model is suitable for the case where the depth of the pre-cutting grooves is less than the penetration of the disc cutter