Search

The electro‐osmosis approach efficiently facilitates the rapid dewatering of soil with high water content and contributes to reducing contaminant levels within the clay soil. However, the changes of chemical field caused by ion transport in the clay soil during electro‐osmosis process will also influence the clay soil consolidation effect. Existing theories predominantly tend to disregard this crucial physical process and its resultant effects, thereby restraining a comprehensive analysis of electro‐osmosis consolidation (EOC) behavior under intricate chemical conditions. This study introduces a concise model of EOC and ion transport considering chemical osmosis. The model considers the nonlinear variation of clay soil parameters such as compressibility, permeability, and effective diffusion coefficients, along with the interaction between EOC and ion transport. Meanwhile, the correctness of the model is verified from different aspects such as theoretical derivation and model comparison. Based on the proposed model, the impacts of the variation in electrical field intensity and chemical concentration on the coupled behaviors between EOC and ion transport are systematically investigated, with and without incorporating nonlinear consolidation characteristics. The results show that diffusion and electro‐migration exhibit a more pronounced effect on ion transport during EOC. Simultaneously, with the increase of ion concentration in clay soil pore solution, the effects of chemical osmosis become increasingly apparent, thereby enhancing clay soil settlement. [ABSTRACT FROM AUTHOR]

A series of microbial-induced carbonate precipitation (MICP) experiments were conducted using Sporosarcina pasteurii to reinforce coastal soft clay in Zhejiang. By analyzing the physical and mechanical parameters of samples of varying ages, specifically focusing on each sample's unconfined compressive strength, triaxial shear strength, and permeability coefficient, it was revealed that MICP technology can be used effectively to reinforce coastal clay. The unconfined compressive strength of treated soil increased by 23% compared to untreated soil, while the permeability coefficient decreased by 75%. The internal friction angle of the clay remained almost constant, whereas cohesion significantly increased by approximately 53%. One-dimensional compression experiments were also performed, yielding consolidation parameters such as the compression coefficient, compression index, and consolidation coefficient. The results indicated a notable decrease in the soil compression index. Furthermore, microscopic analysis revealed that clay particles were cemented by calcium carbonate, whose precipitation was induced by the bacteria. Our XRD results also indicated that the bacteria facilitated the conversion of Ca2+ present in the soil into calcium carbonate. [ABSTRACT FROM AUTHOR]

Medium–long-term photovoltaic (PV) output forecasting is of great significance to power grid planning, power market transactions, power dispatching operations, equipment maintenance and overhaul. However, PV output fluctuates greatly due to weather changes. Furthermore, it is frequently challenging to ensure the accuracy of forecasts for medium–long-term forecasting involving a long time span. In response to the above problems, this paper proposes a medium–long-term forecasting method for PV output based on amplitude-aware permutation entropy component reconstruction and the graph attention network. Firstly, the PV output sequence data are decomposed by ensemble empirical mode decomposition (EEMD), and the decomposed intrinsic mode function (IMF) subsequences are combined and reconstructed according to the amplitude-aware permutation entropy. Secondly, the graph node feature sequence is constructed from the reconstructed subsequences, and the mutual information of the node feature sequence is calculated to obtain the graph node adjacency matrix which is applied to generate a graph sequence. Thirdly, the graph attention network is utilized to forecast the graph sequence and separate the PV output forecasting results. Finally, an actual measurement system is used to experimentally verify the proposed method, and the outcomes indicate that the proposed method, which has certain promotion value, can improve the accuracy of medium–long-term forecasting of PV output. [ABSTRACT FROM AUTHOR]

In response to evaluating the current status and assessing the risk assessment requirements of land subsidence in Ningbo City, the characteristics of land subsidence in recent years were analyzed using InSAR remote sensing monitoring data and subsidence point monitoring data from 2017 to 2020. Based on this analysis, a land subsidence risk assessment system has been developed, primarily consisting of six evaluation factors, including ground elevation, susceptibility to subsidence, cumulative ground subsidence, subsidence rate, urban population density, and the proportion of construction land usage. The susceptibility to subsidence is a comprehensive evaluation factor that takes into account geological conditions, hydrogeological conditions, and the impact of human activities. The results of the land subsidence risk assessment indicate that there are no high-risk susceptibility zones for land subsidence in Ningbo City. Medium and low-risk susceptibility zones are primarily associated with factors such as the thick layers of the Holocene soft soil, historical excessive groundwater extraction, localized high-intensity urban development, and coastal land reclamation projects within the region. Finally, the areas were categorized into medium-risk, low-risk, and risk prevention zones, along with corresponding control recommendations for land subsidence risk management. [ABSTRACT FROM AUTHOR]

For the construction and safe operation of major infrastructure in coastal cities, the impact of regional land subsidence that has occurred or is slowly proceeding deserves attention. Previous studies have mainly focused on the surrounding land subsidence caused during construction or operation, as well as the superposition effect of land subsidence caused by groundwater extraction. However, research on the different impacts of damage due to land subsidence in the construction and operation of urban infrastructure needs to be carried out according to the actual geological environmental conditions, reflected in parameters such as the soil properties and common loads. Numerical simulation cannot fully reflect the details of reality; however, it can avoid the influence of other conditions to focus on different factors influencing land subsidence and thus highlight the contribution of a single factor influencing land subsidence. Therefore, in this paper, we adopt field measurement data and carry out a numerical simulation analysis of different influencing factors. First, taking the Ningbo Jiangdong subsidence center (now located in Yinzhou District) as an example, area growth, cumulative subsidence and the occurrence and development of the subsidence rate of a typical urban subsidence funnel area are analyzed. Then, taking the Ningbo Chunxiao–Meishan area as an example, based on the physical and mechanical characteristics of the main soil layers in the coastal reclamation area, a numerical analysis of the self-weight/backfill and surcharge consolidation settlement of the soil layer (considering the water permeability/impermeability of the bottom surface) and a numerical analysis of the nonuniform settlement caused by pile foundation engineering are carried out. Finally, the Ximenkou–Gulou area is taken as the analysis object. Numerical simulation of metro tunnel pipeline deformation is carried out considering uniform/nonuniform settlement. The results show that the comprehensive prohibition of groundwater exploitation is beneficial to slow the land subsidence rate, while the sedimentation of silty clay in Layer 4 (muddy clay) is the largest among all the soil layers. Compared with uniform settlement, nonuniform settlement is more likely to cause connection failure between tunnel segments. The above research results can provide references for the prevention and control of land subsidence and thus the safe operation of major infrastructure. [ABSTRACT FROM AUTHOR]

Stabilization/solidification (S/S) has been examined as an effective way to strengthen soft soils. However, the presence of organic matter (OM) in dredged marine silt can substantially weaken the reinforcement effect of S/S. To treat organic silt that is difficult to strengthen by S/S, a new combined application of S/S and electroosmosis (EO) treatments was adopted in this paper to increase the strength of soft soil. To enrich the current knowledge about combined soft soil treatment methods, as well as to study the mechanism of increasing the strength under combined S/S-EO treatments, silts with different OM and cement contents were stabilized, and then EO was carried out after certain precuring times. Different test methods, including bearing capacity tests, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), etc., were conducted. The experimental results showed that both OM and cement can reduce the EO resistivity of samples, and the combined application of S/S-EO treatments can significantly improve the bearing capacity of organic silt, with a maximum increase of 80.5%. Additionally, the combined application solves the problem of soil cracking and detachment between electrode and soil. Finally, the micromechanism of S/S-EO is discussed considering the number of cement hydration products and pore diameter. [ABSTRACT FROM AUTHOR]

The uncertainty of renewable energy has brought challenges to the real-time dispatch of integrated energy systems (IES). Nowadays, reinforcement learning (RL) is widely used in IES real-time dispatch to deal with the uncertainty of renewable energy. However, traditional RL algorithms often face the problem of dimensionality when there are numerous controllable units in the system, which will increase operating costs and training time significantly. Based on the above issues, we developed a novel real-time dispatch method for IES with RL model training in stages based on the dueling double deep quality network (D3QN). Dispatches of different controllable units in IES are decomposed into a multi-stage training process according to the degree of thermoelectric coupling and the complexity of equipment operation. This makes the action space of each training stage independent, alleviating the problem of extra-large action space in the traditional RL method. In addition, an improved action-choosing strategy is proposed to enhance local optimization in the process of algorithm training by introducing "offset" according to probability in the training progress. The simulations were carried out on four different types of days in an IES. The results show that the proposed method can effectively reduce operating costs and accelerate convergence. • A multi-stage real-time dispatch method for IES based on RL is proposed. • Number of actions in action space is reduced without increasing discrete interval. • An improved action-choosing strategy is proposed to speed up the convergence rate. • Fixed strategies for units are proposed to participate in the training process. • The effect of the method is evaluated through operating costs and convergence rate. [ABSTRACT FROM AUTHOR]

Background: The method of characteristics (also called as the slip-line method) is used to calculate the bearing capacity of strip footings on ponderable soil. The soil is assumed to be a rigid plastic that conforms to the Mohr-Coulomb criterion. The solution procedures proposed in this paper is implemented using a finite difference method and suitable for both smooth and rough footings. By accounting for the influence of the cohesion c, the friction angle ϕ and the unit weight γ of the soil in one failure mechanism, the solution can strictly satisfy the required boundary conditions. Results: The numerical solution of N are consistent with published complete solutions based on cohesionless soil with no surcharge load. The relationship of N between smooth and rough foundations is discussed which indicates that the value of N for a smooth footing is only half or more of that for a rough footing. The influence of λ ( λ = ( q + ccot ϕ)/ γB) on N is studied. Finally, a curve-fitting formula that simultaneously considers both ϕ and λ is proposed and is used to produce a series of N versus λ curves. Conclusions: The surcharge ratio λ and roughness of the footing base both have significant impacts on N . The formula for the bearing capacity on c- ϕ- γ soil can be still expressed by Terzaghi's equation except that the bearing capacity factor N depends on the surcharge ratio λ in addition to the friction angle ϕ. Comparisons with the exact solutions obtained from numerical results indicate that the proposed formula is able to provide an accurate approximation with an error of no more than ±2 %. [ABSTRACT FROM AUTHOR]