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BackgroundExposure to high levels of heavy metals has been widely recognized as an important risk factor for metabolic syndrome (MetS). The main purpose of this study is to assess the associations between the level of heavy metal exposure and Mets using machine learning (ML) method.MethodsThe data used in this study are from the national health and nutrition examination survey 2003–2018. According to the demographic information and heavy metal exposure level of participants, a total of 22 variables were included. Lasso was used to screen out the key variables, and 9 commonly used ML models were selected to establish the associations with the 5-fold cross validation method. Finally, we choose the SHapley Additive exPlanations (SHAP) method to explain the prediction results of Adaboost model.Results11,667 eligible individuals were randomly divided into two groups to train and verify the prediction model. Through lasso, characteristic variables were selected from 24 variables as predictors. The AUC (area under curve) of the models selected in this study were all greater than 0.7, and AdaBoost was the best model. The AUC value of AdaBoost was 0.807, the accuracy was 0.720, and the sensitivity was 0.792. It is noteworthy that higher levels of cadmium, body mass index, cesium, being female, and increasing age were associated with an increased probability of MetS. Conversely, lower levels of cobalt and molybdenum were linked to a decrease in the estimated probability of MetS.ConclusionOur study highlights the AdaBoost model proved to be highly effective, precise, and resilient in detecting a correlation between exposure to heavy metals and MetS. Through the use of interpretable methods, we identified cadmium, molybdenum, cobalt, cesium, uranium, and barium as prominent contributors within the predictive model.

Relying on the low latency, high reliability, and large bandwidth of 5G networks, the Internet of Things (IoT) can more efficiently promote information interaction and data utilization across remote locations. However, publicly accessible IoT environments involve risks of data and privacy leakage, which threatens the security and feasibility of the cloud-assisted IoT system. Although attribute-based encryption technology provides a fine-grained and secure data sharing solution, it is still challenging to employ dynamic management of multiple groups when device nodes operate cooperatively in dynamic groups. Thus, we propose a dynamic multi-group-supporting policy-hidden secure data sharing scheme in 5G-enabled IoT. Specifically, we exploit a group key management scheme based on the Chinese Remainder Theorem to achieve efficient dynamic group management in IoT and implement concealment of data owners’ access policies to enhance privacy preservation. Moreover, an edge computing layer has been introduced in our 5G-enabled IoT system to entrust decryption to edge servers and cloud servers, thereby mitigating the calculation burden of data users and assisting to fortify resilience against potential collusion attacks. To improve the availability of our system, mechanisms for validating the correctness of the final ciphertext were also incorporated. We further proved the security of the proposed scheme and conducted experimental simulations, which affirm its efficiency and practicability.

With the development of society, a large number of waste autoclaved blocks and gangue on the surrounding environment, in order to protect the environment and reuse resources, these solid wastes have been effectively utilized in the field of grouting reinforcement. This article using waste autoclaved aerated concrete block and waste coal gangue as two kinds of solid waste as the main materials, and mixed with cement to make two kinds of grouting slurry used as goaf foundation treatment and filling, solve the problem of solid waste used in grouting materials resource utilization, realize the transformation of waste into treasure. The test adopted the mixing ratio method, and finally selected the grouting slurry with the most suitable ratio in the aspects of setting time, viscosity, water evolution rate and stone rate, liquidity and compressive strength. The results show that the setting time, viscosity, water extraction rate and stone rate of each WAACBP-cement grout are all in line with the grouting grout standards for goaf foundation treatment, but only 50% and 60% quality replacement rates can be selected for the compressive strength standards. WCGP−cement grout 70% and 80% of the grout in water evolution rate, stone rate and compressive strength do not meet the standard, so can only choose 50% and 60% of the grout ratio, the two kinds of grout in economic perspective analysis, the final selection of 60% of the grout ratio. Finally, performance of the setting time, viscosity, water evolution rate, stone rate, liquidity and compressive strength of the two kinds of grout analyzing, the most suitable grout is WCGP−cement grout.

For the high-speed railway built in the goaf sites, if the influence depth of the additional loads reaches the collapse fault zone of the goaf foundation, the overburden rock mass above the mined area will move again, causing the surface to deform again, which seriously threatens the construction, operation, and maintenance of the high-speed railway lines. Therefore, in order to improve the safety and stability of operation of high-speed railway in goaf sites, it is essential to determine the activation deformation of the goaf foundation. In this paper, based on the additional stress method, the newly added embankment materials are taken as uniformly distributed strip static loads, and the high-speed railway in operation is regarded as the fluctuation-concentrated dynamic loads. The 1/4 vehicle vibration model with two degrees of freedom is introduced, and the influence depth of the additional loads of the goaf foundation is calculated. The criterion of activation is proposed based on the relationship between the influence depth of additional loads and the height of the collapse zone and fault zone. Conclusions drawn are as follows: i) the activation judgment criterion for the goaf foundation under the influence of high-speed railway vibration loads is recommended; ii) case study shows that the rail surface vibration model applicable to quantify the influence depth of high-speed railway mentioned previously mined-out regions; iii) the influence of rail surface irregularity on influence depth cannot be ignored; iv) the research conclusion can provide reference for site selection of high-speed railway and embankment deformation analysis.

Combined with a strategic policy for the recycling of construction waste, this paper puts forward a programme for treating a goaf foundation with waste concrete powder, waste brick powder, and cement grout (BCP cement grout). The BCP cement grout is prepared by replacing part of the waste concrete powder with waste brick powder, and the changeable rule of the setting time, water separation rate, stone rate, and viscosity of the grout with different rates for replacement are studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out. The mineral composition is analyzed and the microscopic mechanism is studied. The results show that the ratio of BCP cement grout developed by the experiment is reasonable; the unit cost is less than 160 yuan/t, which is 40% lower than that of pure cement grout; and both a good economic effect and good environmental effect are obtained. It has the advantages of low water separation rate, high stone rate, and low viscosity. When the ratio of cement powder: waste concrete powder: waste brick powder is 3:5:2 or 3:6:1, the 28 d compressive strength of the stone body is more than 2 MPa, meeting the filling requirements for a goaf foundation. It is not only technically feasible but also economically reasonable to apply construction waste powder to fill the goaf foundation. Recycling and utilizing construction waste can also achieve the ecological restoration of mined-out areas, highlighting the ecological benefits.

Grouting treatment is the main technology to reduce or eliminate the residual deformation and activation deformation of foundations in the goaf sites. Under the influences of the overburden of the mining, the distribution of grouting in goaf foundation is quite different from that of conventional grouting mechanism in porous media. In this paper, considering the time-dependent viscosity and diffusion path of the slurry, the conventional permeation diffusion mechanism of Bingham fluid is derived based on the seepage motion equation in porous media. The theoretical formula is modified according to the fracture distribution characteristics of caving zone and fault zone of the goaf foundation and the superposition effect of porous grouting. Combined with the laboratory test, the theoretical formulas for four working conditions ((i) only considering the time-dependent viscosity, (ii) considering the time-dependent viscosity and diffusion path, (iii) combining the fracture distribution characteristics of goaf foundation, and (iv) combining the fracture distribution characteristics and the superposition effect of porous grouting) are verified, respectively. The results of theoretical formula are used to compare with the design scheme of an engineering example. The research results have an important engineering significance for revealing the mechanism of seepage grouting in goaf foundation and designing the optimal spacing between grouting holes.

At present, the research results for the stress response and deformation characteristics of composite support structures are mostly based on ideal or standard working conditions. External disturbances often exist in practical engineering, which makes the monitoring data deviate from the calculation results. In order to analyze the causes of deviation and correct them in practice, it is necessary to consider the time-varying effect and study the construction mechanics behaviors of composite support structures. Based on in situ test data, the effects of soil predisturbance, excessive excavation, unloading on the surface of edges, the tensioning and lagging of the anchor, and continuous rainfall on the stress-time curves of soil nails were analyzed. On the basis of verifying the effectiveness of the model, ABAQUS finite element software (v.6.10) was used to simulate practical engineering based on ideal working conditions. Comparing the in situ test data and numerical simulation results, the development of mechanical response and deformation characteristics in the process of support structure installation and soil digging and filling were analyzed. Research shows that the time-varying effect has a significant impact on construction mechanics behaviors, especially on soil nailing combined with the use of prestressed anchors, due to layered excavation and support.

Waste concrete powder (WCP) is proposed to replace part of the cement to seek environmentally friendly grouting materials for ground improvement in mine goaf. The optimal mixing proportion was selected based on the performance indexes of the water-separation ratio, stone rate, viscosity, setting time, and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were also conducted to analyze mineralogical phases and investigate the microscopic mechanism. Test results show that the slurry prepared by the substitution rate of 70% and adding 0.05% water-reducing agent meets well the requirements of ground grouting in mine goaf. The WCP produced by grinding mainly exerts microaggregate effect in the slurry due to low activity. A lot of pores on the surface of WCP were shown by SEM which can absorb the water in the slurry and increase the stone rate. The WCP application for ground grouting in mine goaf can not only recycle WC but also provide new grouting materials for goaf ground.

Water-weakening effect is one of the most important factors inducing large deformation and stability problems of shale strata in the Huangjiazhai Tunnel. The influence of water on shale with various water contents and its mechanism still needs more study. In this paper, the X-ray diffraction and water absorption test were first conducted to determine the influence of mineral components on water-rock interaction. Then, a series of rock mechanical tests, including uniaxial compressive test, Brazilian disk test, and triaxial compressive test, were carried out on shale under dried condition, wetted condition with various water contents, and saturated condition. For the uniaxial compression, tension, and triaxial compression, the softening coefficient could reach 0.38, 0.63, and 0.52, respectively. Based on the macroscale experiments, a numerical case study of tunnel excavation was investigated to evaluate the water effect. Finally, with the aid of scanning electron microscope and failure morphology, the mechanism of water-weakening effect on shale was discussed from microscopic and macroscopic perspectives. The thickness of the double layer increases with the increase of water immersion time. This paper provides a set of useful data for reference in construction in shale strata, and a methodology to evaluate water-weakening effect through laboratory and numerical modelling approaches.

Attacking underground caverns with earth-penetrating bombs usually involves multiple explosions in succession. To assess the dynamic responses and cumulative damage of underground caverns under multiple explosions, based on a reduced-scale physical model test, the modified Riedel–Hiermaier–Thoma (RHT) model in the finite-element software LS-DYNA is used to build an underground cavern model that encounters four explosions above the vault. The characteristics of the stress wave attenuation and the evolution laws for the cumulative damage of the surrounding rock in the process of the four explosions are presented. Also, the displacement of the vault, the strain of the cavern wall, and the damage of a rock bolt-supported cavern and an unanchored cavern are compared. The results indicate that the peak pressure is attenuated increasingly in the latter three explosions. The circumferential strain of the cavern wall changes from tensile to compressive from the vault to the corner. The damage of the surrounding rock on the left and right sides of the explosion source is attenuated with increasing distance from the explosion source, and the attenuation curve has a reverse “S” shape. Moreover, the attenuation rate of the curve decreases with each explosion. Multiple explosions do not affect the size of the crushed zone, but they do increase the range of the fracture zone. With each explosion, the cumulative damage of the surrounding rock increases irreversibly, but the damage increment decreases. The cumulative damage of the surrounding rock exhibits a highly nonlinear relationship with successive explosions, and the effect of the rock bolt reinforcement becomes more obvious with successive explosions. Accordingly, the present research results offer a reference for antiexplosion design and support the optimization of underground engineering.

Soil nailing combined with prestressed anchors has a good workability and is relatively cheap in constraining the horizontal displacement. Current research on the technique, whether theoretical analyses, numerical simulations, or model tests, was conducted under ideal working conditions. However, in fact, external disturbances, such as tensioning-lagging of the anchor, are very common and play an important role on stress and displacement. Therefore, it is of great significance to carry out a field test considering the effects of external disturbances, which can obtain real and reliable data through real-time monitoring. In this paper, the impacts of the construction conditions on practical engineering are discussed based on in situ tests, and some reasonable suggestions for the upgrading of misbehaviors in the current construction situation are put forward. In particular, the influence features of soil predisturbance, excessive excavation, unloading on the surface of edges, tensioning-lagging of the anchor, and continuous rainfall on the stress–time curve of soil nails under practical working conditions are analyzed. Behaviors of three different retaining structures enhanced with (i) soil nails; (ii) soil nails and prestressed anchors without unbonded parts; and (iii) soil nails and prestressed anchors with a 2.5 m unbonded part were monitored during staged excavation to investigate the influences of (i) the prestressing force and (ii) the unbonded part of the prestressed anchors on the performance of the entire retaining system. Results show that (i) the prestressing force is the main factor affecting the stress and deformation of the composite retaining system, which is consistent with the existing literature; (ii) the variation of the magnitude and distribution of the soil nail force responding to the anchor prestressing force, however, showed no systematic trend; and (iii) the unbonded part of anchors, which was validated to be the main factor affecting the structural stability in dense materials in the existing literature, is found to have a minor influence in loose fill materials used in this study.