In the process of preparing asphalt-based spherical activated carbon, the molten asphalt must be formed into qualified spherical particles through the granulation process. Taking the process of ...molten asphalt granulation as the research direction, this paper carries out an asphalt rotational viscosity experiment and a thermogravimetric differential thermal experiment (TG-DSC), and obtains the optimal temperature and viscosity values for the asphalt granulation process. The fluent module in ANSYS software is used to input the known asphalt and prilling tower parameters. Based on the asphalt prilling principle, the thermal environment in the prilling tower during on-site melting and asphalt prilling is simulated. The results show that No. 70 matrix asphalt has good fluidity at 135 °C, and that, subsequently, the viscosity of the asphalt is stable and the fluidity of asphalt remains good with the increase in temperature; they also showed that the air velocity is fastest in the central area of the prilling tower, the air temperature is the highest at the top of the tower, and the air temperature in the central area is the lowest at the same height. Finally, a new approach to the granulation process of pitch-based spherical activated carbon is developed, which provides a reference for the basic experimental data and numerical simulation direction for the use of granulation towers to complete the granulation of molten asphalt in industry in the future.
Day by day the call to solve traffic congestion problems is increasing. Subway tunnels and high-speed railway are commonly used for transportation. Therefore, tunnel construction induces soil ...movement, which in turn affects the stability and integrity of adjacent existing buildings. A series of numerical simulations have been established to investigate the effects of tunnel construction of the Greater Cairo Metro–Line 3-Phase-1 on adjacent pile cap foundations of Garage El-Attaba building. Many parameters have been investigated such as tunnel diameter and the distance between pile and tunnel at different tunnel axis and deep and shallow tunnel. After thorough analysis of the results’ simulation, it was found that the tunneling induces additional axial forces and bending moment as well as increasing axial settlement and lateral deflection. Moreover, the results obtained from the parametric study for the shallow and deep tunnel show that the tunnel depth has a much significant effect on piles responses. Finally, the tunnel diameter has an impact on pile responses as well as the pile cap foundation influenced by the tunnel when the tunnel is in very close vicinity of the pile, and its effect is modest to negligible if located far away from the buildings.
An inclined straight combination support pile can play a better role in deep foundation pit support, especially for the protection of adjacent structural pile foundations. We take a section of the ...construction of a deep foundation pit project in Wuhan City, Hubei Province as the research object. This paper studies the influence of inclined and straight combination support piles on the bending moment and displacement behavior of adjacent pile foundations during the construction of foundation pits under the influence of different factors such as distance from the excavation surface, pit angle effect, inclined pile tilt angle, pit depth to width ratio, and construction conditions on the adjacent pile foundation using a three-dimensional finite element model. According to the research results, as the distance from the excavation surface increases, the bending moment of the adjacent pile foundation decreases, and the closer the pile is to the foundation pit, the greater the horizontal displacement of the pile; the bending moment and displacement of the pile foundation are supported by the pit angle effect. Moreover, the pile bending moment increases with the increase of the pit depth–width ratio, and the maximum displacement point of the pile body gradually moves down from the middle of the pile body to the bottom of the pile foundation as the excavation depth of the pit increases. In addition, the minimum displacement of the adjacent pile foundation is at the top of the pile, and the maximum displacement is at the middle of the pile. Finally, compared with the static analysis, the whole process of dynamic simulation can reflect the dangerous working conditions in the project construction process, and make a more complete safety control construction plan for the project construction process.
The high-strain direct testing method is a novel technique for dynamic testing of pile bearing capacity, developed as an improvement to the traditional high-strain method. While its theoretical ...feasibility has been demonstrated through numerical simulations and laboratory experiments, its effectiveness in practical engineering applications remains uncertain. This paper discusses the foundational theory of the high-strain direct testing method, highlighting its clear calculation principles, straightforward process, and advantage of not requiring iterative fitting. The bridge project in Zhuhai, Guangdong Province, China, serves as a case study. An instrumentation layout for concrete-filled piles was designed based on the principles of the high-strain direct testing method, and data processing and analysis programs were developed using Python. Fifteen test piles were selected for field application of the high-strain direct testing method, with detailed analysis conducted on the results from four test piles. The test results were consistent with the soil layer distribution characteristics beneath the four piers of the bridge, validating the feasibility of this method in actual engineering practice. Subsequent static load tests on these four test piles allowed for a comparison with the high-strain direct testing method results, confirming the accuracy and reliability of the high-strain direct testing method for determining the bearing capacity of single piles. Furthermore, this paper identifies sources of error in the application of this method and proposes corresponding improvement measures. As this method directly derives results from instrumented measurements, it is theoretically applicable to piles of any cross-sectional shape and material, provided that enough measurement lines can be successfully arranged along the pile shaft. This capability allows for the real-time estimation of the ultimate bearing capacity during pile driving, thereby enhancing the universality of the high-strain direct dynamic testing method beyond traditional techniques.
Due to their excellent thermal conductivity and sensitivity to temperature changes, special attention should be paid to the influence of temperature on steel-structure bridges. The temperature effect ...is complex, especially for unstable steel arch bridges with complex structural forms. This paper proposes an approximate method that measures the three-dimensional temperature field of the symmetrical arch rib with the two-dimensional temperature field of multiple sections. In addition, it converts the complex radiant intensity calculation of the special-shaped steel box arch rib into the calculation of numerous planar radiant intensities. It uses the ANSYS Workbench to establish the three-dimensional transient thermal analysis finite element model of the No. 2 steel box arch rib. The influence of seasons and arch rib direction on the temperature field of steel box arch ribs and the stress and deformation of steel box arch ribs under non-linear temperature effects were analyzed. The results show that the temperature changes in different seasons significantly impact the temperature changes in the arch ribs. The change in the azimuth angle of the arch rib has a significant impact on the temperature difference between the web plates on both sides of the arch rib; under the influence of the temperature field at the most unfavorable time in summer and winter, symmetrical stress concentration occurs in the arch foot area. Furthermore, the maximum vertical displacement is 13.9 mm and 10.8 mm, respectively. Finally, when the angle is 40°, the maximum temperature difference between the web plates on both sides is 6.9 °C.
In the construction of mountain tunnels, biased and water-rich strata are often encountered. During tunnel excavation, the fluid–solid coupling has a great influence on the stability of the ...surrounding rock. This effect will be more severe when the terrain is biased. The bias tunnel points out the asymmetric load of the rocks which are surrounding the tunnels through the drilling or construction process due to the topographic situation. These loads can cause inverse actions during tunnel construction. Therefore, the effect of fluid–solid coupling on the displacement field, stress field, and seepage field of the tunnel surrounding rock under different biased terrains are studied in this paper. In the context of the Youzishu tunnel project, the numerical model is established to define the degree of terrain bias. Besides, the concept of bias coefficient is introduced. To achieve what is needed, 10 sets of increasing bias coefficients are obtained, by changing the inclination of the terrain to study the influence of formation bias degree on tunnel excavation in water-rich formations. After an in-depth analysis of the simulation results, it is found that the influence of fluid–structure interaction cannot be ignored. By analyzing ten groups of data under different working conditions, the biased terrain will aggravate this effect. As far as the displacement field of the surrounding rock is concerned, the biased formation has a greater impact on the deeply buried side than on the shallow-buried side, and has a greater impact on the vault than on the arch bottom. In addition, by analyzing the stress field and seepage field of the surrounding rock, a similar result can be obtained: the influence of formation bias on the deeply buried side is greater than that on the shallow-buried side, and the biased terrain will increase the pore pressure outside the tunnel lining and increase the water inflow. Finally, the locations where the displacement, stress, water pressure, and water inflow are the largest during the tunnel excavation process are found by the simulations and analyzed. Thus, attention can be paid to these locations, permitting a focus on protection during the construction process.
Tunnel construction will inevitably change the surrounding soil’s original stress and displacement fields, affecting the surrounding piles. In addition, the lateral displacement of the soil at the ...subway tunnel’s face is symmetrically distributed along the tunnel’s central axis, which is greater in the center and smaller on both sides. Therefore, the protection of existing piles and providing a reasonable reinforcement plan have become the focus of attention. Taking a section of Tianjin Metro Line 3 as the research object, this paper studies the influence of the shield tunnel excavation process on the existing pile foundation through three-dimensional finite element simulation. The model has been verified through field monitoring data. Then, parameter analysis has been carried out for two reinforcement measures: grout reinforcement and isolation pile construction. According to the research results, the impact of shield construction on the pile foundation is mainly within the range of twice tunnel diameter to the pile foundation from the front and back of the tunnel face. In addition, the grouting reinforcement has better control of the vertical displacement of the existing pile foundation. The construction of isolation piles can better control the lateral displacement of the existing pile foundation. Have certain reference significance for similar projects.
With the development of all types of new special-shaped arch bridges, the deformation of the pile foundation of special-shaped steel arch bridges has a great influence on the superstructure, and the ...requirements for it are strict. In addition, the force of the inclined pile group under an earthquake is complicated. In this paper, based on the Zhuhai Jindao Bridge project, the finite element numerical model is established in order to study the dynamic response and parameter influence law of an inclined straight pile group foundation under earthquake action. After a thorough analysis of the results of the simulation, it was found that under the action of an earthquake, the inclination angle of inclined piles has a significant influence on the seismic ability of pile group foundations. When the inclination angle of an inclined pile is 5°, the ability of the inclined pile group foundation to resist deformation can be effectively improved, and the load distribution of the pile top is more reasonable.
In all types of new arch bridge structures, the requirements of the foundation are becoming more and more strict. Under the action of horizontal thrust, the distribution of the internal forces of the ...pile group in which inclined piles participate in an arch foundation is complicated. In this regard, the horizontal forces of each pile in a pile group and the horizontal bearing performance of each pile in a pile group under the action of total thrust are investigated by establishing a pile group foundation model and a p-y curve difference equation. After an in-depth analysis of the simulation results, it is found that the load distribution calculated by the finite element method is very close to that calculated by the p-y curve method, both in terms of curve shape and numerical value, indicating that the pile top load distribution is close to the actual situation. In addition, the maximum shear force of each pile body occurs at the top of the pile, and the maximum bending moment occurs at the point 1/5 away from the top of the pile. Finally, the nonlinear analysis of the p-y curve method can be well applied to the calculation of bridge pile foundations.
Ballast tamping is considered as an important maintenance process for railway infrastructures and has a large influence on the capacity of any railway networks. But optimizing the plan of that ...process is a complex problem with a high cost. This paper discusses optimizing tamping operations on ballasted tracks to improve the track geometry and reduce the total maintenance cost. A mathematical model for this problem in the literature is improved here by including the restriction on the resources (tools, workers and budget) in the model and including constant/variable values for track possession cost and available resources. The optimal solutions obtained for all instances are found by using the global optimization. Besides, a numerical study is presented to test and evaluate the model performance. The results show that the proposed model can be adopted by the infrastructure manager (IM) to make suitable tamping scheduling decisions under normal or private conditions; however, the private conditions lead to an increase of the final cost compared to that of the normal ones. Doi: 10.28991/cej-2020-03091601 Full Text: PDF
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