Dynamic Optimization of Construction Time-Cost for Deep and Large Foundation Pit Based on BIM Technology and Genetic Algorithm

Both developing and developed countries are facing a series of difficulties and challenges in the process of urbanization. In recent years, in order to alleviate the problem of urban congestion, underground space has developed rapidly, and the excavation of foundation pit is the most important step in the development of underground space. This paper takes the foundation pit of the tunnel under construction in Suzhou as a research object. The design width of the foundation pit reaches 61.5 m and the depth reaches 18 m, so it belongs to the super wide and deep foundation pit. Numerical analysis is performed by finite element software to calculate the deformation of the foundation pit. The research shows that the main problem to be solved is the deformation of the foundation pit, and the deformation of side wall of foundation pit tunnel is the most obvious. The maximum deformation of the side wall of the main tunnel and the auxiliary tunnel reached the maximum at 15 m. The maximum deformation of the main tunnel is about 1.3 cm, and that of the auxiliary tunnel is about 0.9 cm. Through targeted design and construction, the mechanical performance of the foundation pit retaining structure is optimized, and the stability of the foundation pit is strengthened. The reasonable retaining structure can ensure the good construction quality. The design and construction of the project can provide reference for related engineering construction.

Foundation pit envelope and foundation pit excavation solution design is a multidisciplinary problem that could be linked to a series of safety issues in the geotechnical engineering of an actual construction project. Moreover, the construction of large deep foundation pit in soft soil often faces greater risks and challenges as the support structure deforms more easily and unpredictably. In order to improve the deformation prediction of deep foundation pit engineering precision and efficiency and to ensure that the construction of deep foundation pit engineering is safe and efficient, in this article the traditional MSD (mobilizable strength design) theory research and analysis, combined with the Jinan formation characteristics of a tunnel in JInan, and new parameters were introduced to the original MSD method theory: the wall itself within the bending strain energy U and support compression elastic potential energy of V. A new law of conservation of energy is constructed, and finally, an optimized MSD method has been proposed, this method is shown in the article. Finally, the results of foundation pit deformation calculation were compared among the optimized MSD method, finite element calculation method, and field monitoring data analysis method, so as to demonstrate the reliability of the prediction system of optimized MSD method and finite element analysis method. The results show that, by optimizing the MSD calculation method, the horizontal displacement of the retaining wall varies depending on the excavation depth of the foundation pit and the form of internal support with the overall peak value of displacement between 0∼0.2% H (H being the excavation depth); the deformation of retaining wall increases gradually with the increase of excavation depth of the foundation pit, and the peak position of deformation gradually moves down with the excavation of foundation pit. The trend of these changes is consistent with the results of the finite element method and field data analysis method, proving that the optimized MSD method is reliable in predicting the deformation of the foundation pit under specific stratum conditions.

The excavation depth of a deep and large foundation pit of a composite support system is 25.5 m, the minimum clear distance from the main structure of the station is 10.6 m and the closest distance to the entrance and exit structure is only 3.6 m. Relying on this project, numerical simulation, field monitoring and other methods are used to study the deformation law of the self-supporting system, the ground settlement and the subway station under construction. Then, the influence of different support parameters on the deformation of the subway station and track is analyzed, and the internal relationship between the deformation value of the station and track and the support parameters is further discussed. The main work and achievements are as follows: (1) Through field measurement and analysis, the deformation history of the station and track in the excavation is studied. The obtained results show that the interbracing + pile–anchor composite support structure has better control over the deformation of adjacent stations and tracks. Comparing the simulated value of station and track deformation with the measured data, it is concluded that the simulated and measured deformation trends remain consistent, and the maximum deformation value corresponds to the middle position of the foundation pit. This confirms the rationality and reliability of the composite support system model. (2) The analysis of the influence of different support parameters on the maximum deformation value of the subway station and track shows that the deformation of the station and track is less affected by the pile diameter of the retaining pile and the size of the interbracing section. It is greatly affected by the embedding depth of the retaining pile and the number of support channels. It is suggested that the optimal parameters should be a pile diameter of 1.0 m, embedding depth of 8 m, four interbracings and an interbracing section of 1.0 m × 1.0 m.

With the development of science and technology, there has been growing the grid size, the growing demand for electricity and the extent of increasing the electricity market.In this paper, a mathematical morphology and genetic algorithm based dynamic reactive power optimization method for distribution network is proposed.By means of constructing mathematical morphology filter, the binary image composed by allelic genes of chromosome is filtered and the problem that deals with the action times of voltage regulating devices for compensation is turned into filtering problem of discrete binary image.With further automate scheduling, distribution automation and unmanned substation reactive power optimization of distribution line running made an urgent request.Reactive power optimization can improve the voltage passing rate, increasing the reliability of the system, the power quality, and the system runs the security and economy of the perfect combination, very broad application prospects.

In the construction of high-rise buildings, the effect produced by the excavation of deep and large foundition pits on the surrounding structures cannot be ignored. This paper presents a case study from a construction project located in Nanjing, in which the dynamic excavation process of a founditon pits is numerically analyzed with finite element method on Plaxis. The impact of various excavation stage on subway tunnel nearby is achieved in terms of the results of data analyses and assessments.

The Plaxis 2D finite element software is used to analyze the deformation laws of new pile-soil-support system with HS model based on a foundation pit in Shanghai. Contrastive analysis is conducted between finite element and measured values. The results show that the Plaxis 2D can predict the deformation of the new pile-soil-support system. The existence of steel tube inclined brace changes the deformation laws of the traditional double- row piles and can reduce the displacement of top of the double-row piles effectively. The deformation of retaining piles of the new pile-soil-support system satisfies the safety and deformation requirements of the foundation pit. The new support system has no inner supports and it avoids a lot of construction waste generated by the construction and demolition of temporary supports. It is safe, economy and green environmental protection, and it can provide reference for the deep and large foundation pits in soft soil areas.

Deep foundation pit excavation is a basic and key step involved in modern building construction. In order to ensure the construction quality and safety of deep foundation pits, this paper takes a project as an example to analyze deep foundation pit excavation technology, including the nature of this construction project, the main technical measures in the construction of deep foundation pit, and the analysis of the safety risk prevention and control measures. The purpose of this analysis is to provide scientific reference for the construction quality and safety of deep foundation pits.

Traditional microgrid lacks rotational inertia and it needs to operate in the economic state. A dynamic power optimization strategy is proposed for microgrid based on the virtual synchronous generator's frequency regulation characteristics in this paper. Load in microgrid is divided into planned load and unplanned load. The optimization model with the goals of minimizing the generation operation cost and the transmission power of the linking-up road is established to distribute the planned load. The genetic algorithm-simulated annealing algorithm is used to solve the optimization model. Active power generation plans for the VSGs are formulated in the light of calculation results. Central controller estimates the power fluctuation value when unplanned load fluctuations occur in the microgrid. VSG's output power is dynamically adjusted based on the principle of equal marginal cost to achieve dynamic power optimization of microgrid. The effectiveness of the proposed control strategy is verified by simulation.

Multi-objective non-simultaneous dynamic optimal control for an ejector expansion heat pump with thermal storages

With the rapid development of domestic super high-rise buildings in China, both the scale and depth of deep foundation pit projects keep expanding, and more deep foundation pits appear in the areas with dense buildings and population, which puts forward higher requirements for the design and construction of foundation pit projects. However, the present 2D survey data are incomplete and inaccurate, which restricts the effective application of geotechnical survey data by all parties involved in the project. The BIM technology, with its own characteristics of 3D visualization and parameterization, is able to apply the information of abstract and complex survey data to construct a digital 3D model with given geological information data. Then, communication and decision-making according to the digital 3D geological BIM model will improve the scientificity of engineering design scheme and construction scheme. This paper takes the BIM application in the foundation pit and basement engineering of the Qianhai Trading Plaza Project an example, to elaborate the application process of BIM technology in complex geology and pile foundation engineering. The feasibility of BIM application is demonstrated by comparing and analyzing the real data of the project. The study is able to provide reference for the construction of similar complex geological foundation pit.

A comparative study on the performance of dissortative mating and immigrants-based strategies for evolutionary dynamic optimization

Aiming at the problems such as low computational efficiency and long process in dynamic topology optimization, combined with bi-directional evolutional structure optimization, the dynamic optimization problem is transformed into the static optimization problem in multiple load cases. Newmark method is used to analyze the structure dynamics load. The topology optimization model based on equivalent static load is established. On the basis of the equivalent static load, multi-objective dynamics evolutionary structure optimization is studied. And the mathematical model of the dynamic stiffness and natural frequency about the multi-objective optimization is established. The mathematical formula of the sensitivity is deduced. Then a complete optimization iterative process is given. The numerical example illustrates that it is feasible to solve the multi-objective dynamic topology optimization with equivalent static loads. Modal tracking technique is introduced to the multi-objective dynamic topology optimization. The numerical example shows that modal tracking technology can track the required modal in the optimization process.

Generating motion and capturing motion of an articulated body for computer animation is an expensive and time-consuming task. Conventionally, animators manually generate intermediate frames between key frames, but this task is very labor-intensive. This paper presents a model-based singularity-free automatic-initialization approach to capturing human motion from widely-available, static background monocular video sequences. A 3D human body model is built and projected on a 2D projection plane to find the best fit with the foreground image silhouette. We convert the human motion capture problem into two types of parameter optimization problems: static optimization and dynamic optimization. First, we determine each model body configuration using static optimizations for every input image. Then, to obtain better description of motion, the results from all static optimizations are fed into a dynamic optimization process where the entire sequence of motion is considered for the user-specified motion. The user-specified motion is defined by the user and the final form of the motion they want. A cost function for static optimization is used to estimate the degree of overlapping between the foreground input image silhouette and a projected 3D model body silhouette. The overlapping is computed using computational geometry by converting a set of pixels from the image domain to a polygon in the real projection plane domain. A cost function for dynamic optimization is the user-specified motion based on the static optimization results as well as image fitting. Our method is used to capture various human motions: walking, pushing, kicking, and handshaking.KeywordsInput ImageDynamic OptimizationModel BodyComputer AnimationParameter Optimization ProblemThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Deep foundation pit construction adjacent to a subway station in a soft soil area was numerically simulated with Midas GTS NX calculation software. The influence of the deep foundation pit construction on the deformation and stress of the subway station structure was studied, and the influence of the foundation pit retaining structure on the station was analyzed. The results show that during the foundation pit excavation process, the subway station slab rose as a whole and was greatly affected by the deformation of the common ground connecting wall, with the most unfavorable position changing as the excavation area changed. The excavation of foundation pits in different zones had a considerable influence on the east‐to‐west displacement of the common diaphragm wall outside the foundation pit. The maximum positive bending moment of the common diaphragm wall changed little, while the negative bending moment increased greatly during construction. Overall, the foundation pit excavation had a great impact on the negative moment of the common diaphragm wall. During the foundation pit excavation process, the subway station column lifted upward, and the maximum displacement, which was located at the west end of the station near the foundation pit, gradually weakened from west to east. As the foundation pit excavation process continued, the maximum axial force of the station column increased by 10.38%, and the pressure was the largest in the middle column. As the thickness of the diaphragm wall increased, the stiffness of the foundation pit retaining structure increased. After earthwork excavation and unloading, the locations in the retaining structure with high stiffnesses could resist deformations. The whole foundation pit was offset due to the high stiffness of the foundation pit retaining structure, which increased the horizontal deformation of the existing station structure. With increasing thickness, the relative horizontal deformation of the station slab gradually increased, mainly because the difference between the depths of the old and new diaphragm walls caused the embedded soil of the two same deep foundation pits to differ. Furthermore, there were great differences in the Earth pressure behind the wall. As the depth of the diaphragm wall increased, the active Earth pressure behind the diaphragm wall increased.

So far, there have been a large number of diaphragm walls in the Yangtze River Delta as engineering examples of deep foundation pit maintenance structures in subway stations, but there is a lack of systematic research and summary on the deformation characteristics of ground connecting walls. This study aimed to clarify the deformation law of the diaphragm wall during the excavation of a deep foundation pit in a soft soil region. Based on the monitoring data of the diaphragm wall of the deep foundation pit of the Hangzhou metro station, the monitoring data of the deep foundation pits of 15 subway stations in Shanghai and Ningbo cities around Hangzhou were considered. Grouping and classification methods were used to analyze the similarities and differences in the deformation characteristics of the diaphragm wall in the three regions. The results indicate the following: the maximum lateral deformation of the diaphragm wall in Hangzhou increases linearly with the relative depth of the maximum lateral deformation. The maximum lateral deformation of the foundation pit in Hangzhou is 0.072% H∼0.459% H, with a mean of 0.173% H. The wall deformation in Hangzhou varies significantly with the depth of the foundation pit, but the influence of the depth of the foundation pit on the wall deformation is considerably less than that in Shanghai and Ningbo. The corresponding position of the maximum lateral deformation in the excavation depth increases linearly with the excavation depth of the foundation pit, and the corresponding position of the lateral deformation of the diaphragm wall in Shanghai is more affected by the excavation depth of the foundation pit. The lateral deformation of the diaphragm wall increases rapidly in the range of 0 H–0.5 H, and the maximum lateral deformation occurs at 0.5 H–1.1 H.