Abstract:

In order to explore the influence of rise-span ratio on the mechanical properties of Pipe-Roof Pre-construction (PRP) structures in underground engineering, mechanical tests on two PRP structure members were designed and completed with rise-span ratio as a parameter. Through the comparative analysis of load-deflection curves and strains of steel pipe curtain and concrete section, the failure process and failure mode of different rise-span ratio specimens were explored, and the influence of rise-span ratio on the mechanical properties of members was analyzed. A numerical calculation model was established to further explore the influence of rise-span ratio, concrete strength and reinforcement ratio on the bearing capacity of the PRP structure arch members. The results show that with fixed end constraints, the bending failure mode of the PRP structure arch members is presented under symmetrical concentrated load. The change of rise-span ratio has a great influence on the bearing capacity of the PRP structure arch members. When the rise-span ratio increases from 0.048 to 0.102, the ultimate bearing capacity and stiffness of the members become larger. The concrete strength and reinforcement ratio have little effect on the ultimate bearing capacity of the members.

Abstract:

In order to investigate the wind uplift resistance and failure behavior of the Continuous Welded Stainless Steel (CWSS) roof system, a combination method of static wind uplift test and numerical simulation was adopted to compare the differences in failure modes and ultimate bearing capacities of the CWSS roof system with and without sliding support imperfections. The wind uplift resistance response of the CWSS roof system was simulated using the finite element method, and further parametric studies were carried out based on the verified model. The research results show that the initial support imperfections can significantly reduce the wind uplift resistance of the CWSS roof system. When 1, 2, and 3 supports are removed, the ultimate wind pressure is reduced by 10.7%, 23.3%, and 35.7%, respectively. Reducing the width-to-thickness ratio of the roof panel has little impact on the overall ultimate bearing capacity of the roof but can enhance the flexural rigidity. Increasing the thickness of the support can notably improve the wind uplift resistance of the roof system.

Abstract:

In order to study the influence of vertical loads on the dynamic response of pile group foundation in liquefiable ground, the high cap pile group is taken as the research object. The shaking table test is used to take 5%, 10%, 15% and 20% of the ultimate vertical bearing capacity of the pile foundation as the vertical load, and the test is carried out under the seismic intensity of 0.20g, 0.34g and 0.50g. The effects of different vertical loads on sand liquefaction and dynamic response are analyzed from aspects of pore pressure ratio time history, acceleration time history, pile cap displacement time history and pile bending moment response time history. The results showed that with the increase of vertical load, the peak pore pressure ratio and the liquefaction degree of sand decreased. The peak values of pile top acceleration, pile cap displacement and pile bending moment decreased first and then increased with the increase of vertical load, and the values were the smallest when the vertical load was 15%. The increase of vertical load can inhibit the liquefaction of sand and increase the inertial force of the structure. With the combined influence, the dynamic response effect of pile group in liquefiable ground is optimal under the vertical load of 15%.

Abstract:

To thoroughly investigate the feasibility of carbon fiber anchor cable support in coastal deep excavations, a field test was conducted on cast-in-place pile+prestressed carbon fiber anchor cable support based on a deep excavation project in Yantai City. This study analyzed the prestress loss laws and deformation patterns of the deep foundation pit during excavation under the action of prestressed carbon fiber anchor cables using a complete set of construction techniques. The study results show that the prestressed carbon fiber anchor cable has been successfully applied in coastal deep foundation pit support projects.

Abstract:

To analyze the drained uplift bearing capacity of suction anchors in soft clay seabed, a statistical damage model based on the Weibull distribution function was established for the saturated clay-structure interface, integrating the principles of damage mechanics and the Mohr-Coulomb strength criterion. Subsequently, a simplified shear displacement method for the uplift bearing capacity of suction anchors was proposed. A series of ring shear tests of saturated clay-steel interface were conducted to determine the model parameters and validate the accuracy of the model. It is found that the drained shear of saturated clay-steel interface exhibits significant strain softening characteristics. During the uplift process of suction anchors, stress redistribution occurs at the clay-anchor interface, leading to its progressive failure. For the same area of anchor wall, increasing the anchor length is more beneficial for enhancing the drained uplift bearing capacity of suction anchors compared to increasing the anchor diameter. Additionally, the stress level is a critical factor influencing the shear strength of clay-anchor interface. In practice, prioritizing sites with higher soil density can effectively improve the uplift bearing performance under drainage conditions.

Abstract:

The water retention and anti-cracking ability of clay soils improved by lignin-derived polymer are studied by indoor evaporation tests. To explore the crack evolution patterns during the wet-dry cycle, the effects of different contents of polymer on internal moisture variation in improved soils were analyzed and the quantitative analysis was carried out for crack network on the soil surface using relevant image analysis software. The results show that: (1) The water retention capacity of improved soil is initially enhanced and then declined with increasing polymer content. When the content is 1.0%, the duration of the constant evaporation rate stage is extended by about 4 hours compared to the untreated soil and the average evaporation rate of this stage is reduced by about 22.95%. (2) The development of surface cracks is effectively limited by aggregating soil particles and water. However, excessive addition of polymer causes local stress concentration and induces extensive crack development. (3) The moderate content of polymer suppresses the development of cracks and the formation of wide cracks, thus enhances the "healing" capability of crack network during the wet-dry cycle.

Abstract:

To investigate the effect of iron oxides on consistency limits of clayey soil, the ordinary clay from Guilin was selected as the parent soil for this study, and mixed soil samples of iron oxides and NaNO₃ as well as soil samples added with NaNO₃ alone were prepared. Tests were conducted to study the variation of consistency limits under different temperature and dosage conditions, and the particle size analysis and microstructural test were conducted to explain the mechanism of iron oxides’ influence on soil particles. The test results showed that NaNO₃ reduced the consistency limits of Guilin clay. The greater the dosage was, the more obvious the reduction in consistency limits was. The trends of liquid limit, plastic limit and shrinkage limit changes were consistent. Iron oxides increased the liquid limit, plastic limit and shrinkage limit of Guilin clay after the addition of NaNO₃, and the liquid limit increased the most, followed by plastic limit and shrinkage limit. This enhancement effect intensified with the increase of iron oxide concentration and weakened with the rise of temperature. After drying the mixed soil at 105 ℃ for 48 hours, the effect of iron oxides on liquid limit, plastic limit and shrinkage limit was nearly eliminated. High-temperature drying alters the interaction between iron oxides and soil particles and affects the particle size, thereby influencing the consistency limits of soil.

Abstract:

In order to optimize the performance of modified high-performance building gypsum, a 0.20% vegetable protein retarder was used to delay the setting time of the building gypsum. The response surface methodology was employed to design a series of experiments involving the combined use of three admixtures: polyether modified silicone defoamer, redispersible latex powder, and hydroxypropyl methylcellulose. The experimental response indicators were analyzed, and the Design-Expert 12 software was used to set optimization conditions for these response indicators. Based on the Optimization function, optimal parameters for the dosage of each admixture were generated, and the feasibility of the optimization results was verified. The results indicated that the optimal admixture dosages for the high-performance building gypsum were 1.051% polyether modified silicone defoamer, 0.827% redispersible latex powder, and 0.141% hydroxypropyl methylcellulose. When comparing the modified high-performance building gypsum with the unmodified version, significant improvements were observed in six performance metrics: absolute dry flexural strength, absolute dry compressive strength, tensile bond strength, water retention rate, softening coefficient, and porosity.

Abstract:

To synthesize high-performance rare earth composite luminescent materials, blue fluorescent Nitrogen Doped Graphene Quantum Dots (N-GQDs) were prepared by hydrothermal method, and an N-GQDs modified composite luminescent material UiO-66-(COOH)₂-Eu was prepared by post-synthetic modification method. The structural morphology of the composite luminescent material was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The fluorescent and luminescent properties of the composite material were tested, and the effect of N-GQDs dosage on the luminescent properties was discussed. The results show that the obtained composite luminescent material has good stability and fluorescent properties, and a small amount of N-GQDs can improve the luminescence intensity and prolong the fluorescence lifetime of the composite material.

Abstract:

To systematically explore place perception in historical and cultural districts and its impact on cultural heritage protection behavior, this study takes the Kaifeng Shudian Street historical and cultural district as a case. Using grounded theory, five core dimensions of place perception were identified: historical culture, architectural space, commercial consumption, environmental atmosphere, and facility function. A "place perception-place meaning-sense of place-cultural heritage protection behavior" model was then constructed and validated using structural equation modeling. The results indicate that historical culture, architectural space, and environmental atmosphere have significant positive effects on cultural heritage protection behavior, while commercial consumption and facility function mainly exert indirect effects through place meaning and sense of place. Place meaning plays a cognitive mediating role between place perception and sense of place, whereas sense of place serves as an emotional mediator between place perception and cultural heritage protection behavior. Based on these findings, this study proposes place perception-oriented district renewal strategies, providing practical guidance for the protective renewal of historical and cultural districts and offering reference for sustainable development in other urban districts.

Abstract:

In order to deeply study the surface movement law during mining under a thick loose layer, taking the Heze mining area in Shandong Province as an example and based on the field measurements of surface deformation, 12 numerical models were established using FLAC3D at different thickness ratios of the loose layer to the bedrock (hereinafter referred to as the loose-to-base ratios) ranging from 0.25 to 5.00. The surface deformation parameters were obtained, analyses were carried out on the stress of the overlying rock and the characteristics of surface deformation, and studies were conducted on the variation law of the surface deformation parameters. The results are as follows: (1) The surface subsidence coefficient is relatively large and the surface subsidence response is rapid because of the combined influence of the thick loose layer and the aquifer subsidence caused by water loss. The starting distance is 0.2H (H represents the average depth). The recession characteristics of the boundary area of the subsidence basin are obvious, and expand rapidly first and then slow down until finally converging. (2) When the mining depth remains constant, as the loose-to-base ratio keeps rising, the subsidence coefficient initially goes up and then declines. The horizontal movement coefficient first increases, subsequently decreases, and ultimately becomes stable. The tangent of the main influence angle also shows an upward-then-downward trend. It is found that when the loose-to-base ratio ranges from 1.50 to 2.00, the surface deformation attains its peak value. (3) Above the center of the goaf, the failure of the overlying rock is mainly tensile failure. As the loose-to-base ratio increases, the tensile stress first increases and then decreases. Above the boundary of the goaf, it is affected by both tensile and compressive stresses. The compressive stresses on both sides of the goaf decrease as the loose-to-base ratio increases.

Abstract:

To address the significant load swing caused by unknown external forces during the hoisting process of bridge cranes, a neural network Sliding Mode Controller (SMC) with parameter optimization based on an improved honey badger algorithm is proposed. First, a Radial Basis Function (RBF) neural network is employed to effectively approximate the unknown external forces in the dynamic model of the crane system. The output of this approximation is then fed into the SMC to ensure the asymptotic stability of the crane system during the hoisting process. Next, the Chebyshev chaos population mechanism and Gaussian mutation strategy are introduced to improve the standard honey badger algorithm, enhancing its optimization ability for the rate parameters of the RBFSMC and thereby reducing system oscillations. Finally, through comparative simulations with SMC, RBFSMC, and particle swarm optimization-RBFSMC controllers, the proposed controller is shown to achieve better positioning, output driving force, and anti-swing control performance, demonstrating its superior effectiveness in precise positioning and sway suppression for the crane system.