Numerical Analysis of Reinforced Concrete Piles under Blast Loads

Pile foundations are commonly used as foundation systems for high-rise buildings and bridges. This paper uses a fully coupled three dimensional numerical modelling procedure to study the performance of pile foundations subjected to ground shocks induced by surface explosions. The comprehensive numerical model includes the pile, surrounding soil, air and the explosive. Appropriate material models are incorporated and dynamic non-linear analysis is carried out using finite element techniques.  The soil in which the pile is buried could influence the blast performance of the pile. A parametric study is hence carried out to evaluate the effects of soil properties of density, friction angle, cohesion and Poisson’s ratio on the blast performance of the pile. It is found that density and cohesion of soil have significant effects on the deflection of the pile under blast loading. Poisson’s ratio has some effect, but effect of the soil friction angle is not very significant. The findings of this study will serve as a benchmark reference for future analysis and design of pile foundations to blast loading

An analytical model for shear behaviour of bolted rock joints

Rock bolts have been widely used to reinforce the jointed rock mass. Modelling the mechanical shear behaviors of the bolted rock joints are difficult due to the complex interactions between bolts and rock joints. The applied pretension forces combined with the axial loads developed in the bolt act as the normal forces which are applied to the rock joints. However, these combined normal forces are not considered in the existing analytical models. An analytical model is proposed in this study to predict the shear behavior of the bolted rock joints, by taking into account the pretension forces, the axial forces developed in the bolt, the interfacial bond stress between the bolt and grout, and dowel shear loads acting transversely to the bolt axis. The proposed analytical model is able to provide complete curves of the dowel shear loads, axial loads, and the global shear loads as a function of the joint shear displacement. The analytically predicted axial load vs shear displacement curves and the global shear load vs shear displacement curves are verified by available experimental tests. The validation shows that the proposed model has the capacity to predict the global shear load evolution as well as the axial load evolution. The factors such as the pretension forces, the bolt inclination angles, the concrete strength and the rock joint friction are successfully accounted for in the analytical model

Numerical investigation into the blasting-induced damage characteristics of rocks considering the role of in-situ stresses and discontinuity persistence

This paper presents a 3D coupled Smoothed Particle Hydrodynamics (SPH) and Finite Element Method (FEM) model, which was developed to investigate the extent of damage zone and fracture patterns in rock due to blasting. The RHT material model was used to simulate the blasting-induced damage in rock. The effects of discontinuity persistence and high in-situ stresses on the evolution of blasting-induced damage were investigated. Results of this study indicate that discontinuity persistence and spatial distribution of rock bridges have a significant influence on the evolution of blasting-induced damage. Furthermore, high in-situ stresses also have a significant influence on the propagation of blasting-induced fractures, as well as the patterns of fracture networks. It is also shown that the blasting-induced cracks are often induced along the direction of the applied high initial stresses. Moreover, additional cracks are normally generated at the edges of the rock bridges probably due to the relatively high stress concentration

Three-dimensional DEM investigation of the fracture behaviour of thermally degraded rocks with consideration of material anisotropy

A complete understanding of the fracture behaviour of anisotropic rocks under elevated temperatures is fundamentally important for rock and reservoir engineering applications. This paper shows a three-dimensional numerical investigation of the fracture behaviour of anisotropic sandstone, with consideration of the effects of temperature and material anisotropy. In the study, a 3D semi-circular bend (SCB) model was established by using the Discrete Element Method (DEM). The thermal responses of different minerals and the strength anisotropy of incipient bedding planes were considered in the model. The DEM model was calibrated against a series of laboratory experiments on Midgley Grit sandstone (MGS) that exhibits intrinsic anisotropy. The pure mode I, mode II, and mixed-mode (I+II) fracture characteristics of the MGS were investigated under elevated temperatures (up to 600 °C) using the established DEM model. The thermal degradation (i.e., fracturing) of the rock, the fracture load, the evolution of micro-cracks, and the stress-strain relationship around notch tips were analysed, with emphasis on enlightening the micro-mechanisms underlying the fracture behaviour. The results of the study were discussed and then compared with experimental observations and theoretical predictions

Performance enhancement of horizontal extension and thermal energy storage to an abandoned exploitation well and satellite LNG station integrated ORC system

Tens of millions of abandoned exploitation wells (AEW) exist throughout the world, posing a threat to the environment and costing extra investment for decommissioning. Revitalization of the AEW offers a cost-effective solution for geothermal energy exploitation by saving the high costs of decommissioning and drilling. However, the thermal resources from AEW are usually of low and medium grade. Measures should be taken to increase the efficiency of AEW geothermal power plants. Meanwhile, the regasification process of satellite liquified natural gas (LNG) stations worldwide suffer from a loss of high-grade cold energy. Various studies have used geothermal heat and LNG cold to produce electricity, yet the horizontal extension of the AEW that may increase the recovered temperature, and the fluctuation of the LNG flow that may reduce the power output, were not discussed. This study proposes and evaluates a novel integrated organic Rankine cycle (ORC) system that uses the geothermal heat from the AEWs and waste LNG cold energy from satellite LNG stations, focusing on the performance enhancement of horizontal extension to increase the geothermal temperature and thermal energy storage to stabilize the LNG cold energy supply. A numerical model is developed that considers the horizontal extension in the AEW, and the horizontal extension is found to significantly increase the geothermal fluid temperature. A machine learning-based predictive model is built to assess the AEW outlet temperature under given parameters and working conditions. Cold thermal energy storage (CTES) modules are designed and optimized to stabilize the waste cold energy recovery when exposed to highly fluctuating LNG supply during off-design operation. CTES increased the ORC efficiency by 38.5% and has the potential to significantly shorten the payback period. Therefore, by utilizing the horizontal extension of the AEW and combining the power generation with LNG cold through thermal energy storage, the zero-emission geothermal and waste cold energy-based system can be a viable solution for future AEW revitalization and LNG waste cold energy utilization

Effect of additives and moisture on the fermentation quality and bacterial community of high moisture ear corn

Maize (Zea mays L) is one of the most widely cultivated crops used as energy feeds. The aim of this study was to evaluate the effects of two lactic acid bacteria additives on the fermentation quality and bacterial community of high moisture ear corn (HMEC) silage at different moisture levels. The study utilized corn kernels and cobs harvested at the stage of complete ripeness as the primary material. The cob was crushed and divided into three treatment groups: an untreated control group (CK), a group treated with a mixture of Lactobacillus plantarum and Lactobacillus brucei (TQ), or a group treated with a mixture of Lactococcus lactis and Lactobacillus brucei (KT). Moisture contents were adjusted to 37.5% (L), 42.5% (M) or 47.5% (H) and then silaged for 180 days. Compared to CK, TQ, and KT elevated the dry matter, crude protein, starch, lactic and acetic acid content of HMEC and reduced the pH, neutral detergent fiber, acid detergent fiber and ammonia nitrogen content (p < 0.05). Even though both additives improved the bacterial community structure after fermentation, KT experienced the greater enhancement. At a phylum and genus level, KT had the higher relative abundance of Firmicutes and Lactobacillus, respectively. Compared with the group of 37.5% (L) moisture content, the 42.5% (M) and 47.5% moisture content (H) group increased lactic acid, acetic acid and ammonia nitrogen concentrations and reduced the pH value (p < 0.05). In conclusion, the addition of TQ and KT at the appropriate moisture content might be helpful for producing high-quality HMEC. Among the three moisture contents, 42.5% (M) moisture content provides the best silage qualities

Systemic immune-inflammation index is associated with aneurysmal wall enhancement in unruptured intracranial fusiform aneurysms

IntroductionInflammation plays a key role in the progression of intracranial aneurysms. Aneurysmal wall enhancement (AWE) correlates well with inflammatory processes in the aneurysmal wall. Understanding the potential associations between blood inflammatory indices and AWE may aid in the further understanding of intracranial aneurysm pathophysiology.MethodsWe retrospectively reviewed 122 patients with intracranial fusiform aneurysms (IFAs) who underwent both high-resolution magnetic resonance imaging and blood laboratory tests. AWE was defined as a contrast ratio of the signal intensity of the aneurysmal wall to that of the pituitary stalk ≥ 0.90. The systemic immune-inflammation (SII) index (neutrophils × platelets/lymphocytes) was calculated from laboratory data and dichotomized based on whether or not the IFA had AWE. Aneurysmal symptoms were defined as sentinel headache or oculomotor nerve palsy. Multivariable logistic regression and receiver operating characteristic curve analyses were performed to determine how well the SII index was able to predict AWE and aneurysmal symptoms. Spearman’s correlation coefficients were used to explore the potential associations between variables.ResultsThis study included 95 patients, of whom 24 (25.3%) presented with AWE. After adjusting for baseline differences in neutrophil to lymphocyte ratios, leukocytes, and neutrophils in the multivariable logistic regression analysis, smoking history (P = 0.002), aneurysmal symptoms (P = 0.047), maximum diameter (P = 0.048), and SII index (P = 0.022) all predicted AWE. The SII index (P = 0.038) was the only independent predictor of aneurysmal symptoms. The receiver operating characteristic curve analysis revealed that the SII index was able to accurately distinguish IFAs with AWE (area under the curve = 0.746) and aneurysmal symptoms (area under the curve = 0.739).DiscussionAn early elevation in the SII index can independently predict AWE in IFAs and is a potential new biomarker for predicting IFA instability

Cathelicidin-BF, a Snake Cathelicidin-Derived Antimicrobial Peptide, Could Be an Excellent Therapeutic Agent for Acne Vulgaris

Cathelicidins are a family of antimicrobial peptides acting as multifunctional effector molecules in innate immunity. Cathelicidin-BF has been purified from the snake venoms of Bungarus fasciatus and it is the first identified cathelicidin antimicrobial peptide in reptiles. In this study, cathelicidin-BF was found exerting strong antibacterial activities against Propionibacterium acnes. Its minimal inhibitory concentration against two strains of P. acnes was 4.7 µg/ml. Cathelicidin-BF also effectively killed other microorganisms including Staphylococcus epidermidis, which was possible pathogen for acne vulgaris. Cathelicidin-BF significantly inhibited pro-inflammatory factors secretion in human monocytic cells and P. acnes-induced O2.− production of human HaCaT keratinocyte cells. Observed by scanning electron microscopy, the surfaces of the treated pathogens underwent obvious morphological changes compared with the untreated controls, suggesting that this antimicrobial peptide exerts its action by disrupting membranes of microorganisms. The efficacy of cathelicidin-BF gel topical administering was evaluated in experimental mice skin colonization model. In vivo anti-inflammatory effects of cathelicidin-BF were confirmed by relieving P. acnes-induced mice ear swelling and granulomatous inflammation. The anti-inflammatory effects combined with potent antimicrobial activities and O2.− production inhibition activities of cathelicidin-BF indicate its potential as a novel therapeutic option for acne vulgaris

The vertex-to-vertex contact analysis in the two-dimensional discontinuous deformation analysis

In the two-dimensional discontinuous deformation analysis (DDA), contacts can be generalized into three types: vertex to edge, edge to edge, and vertex to vertex. In the vertex–edge contact, the contact reference edge is clearly and uniquely defined, while the contact reference edge for the vertex–vertex contact is not unique, which will lead to an indeterminate state. The indeterminacy of the vertex–vertex contact is a well-known problem in both the continuum-based methods and the discontinuum-based methods. The standard DDA employs the shortest path method to deal with the indeterminacy in the vertex–vertex contact, which is sensitive to the choice of analysis parameters, such as the time step size, the maximum displacement ratio and the contact spring stiffness. Two enhancements to the shortest path method are introduced in this paper. The first enhancement employs a temporary vertex–vertex contact spring to determine the moving tendency among two contact blocks. The second enhancement uses the trajectory of the vertex during a time step to find the entrance edge when the moving vertex invades into the target block. Examples show that these two enhancements to the standard DDA code work well

Influence of fracture deformation on grout penetrability in fractured rock masses

Fracture deformation during grouting is a hydro-mechanical coupled dynamic process. Some studies indicated that an increase in grouting pressure can accelerate the grouting process, while some other investigations concluded that a high grouting pressure would weaken the grouting effect for fine fractures due to fracture deformation. Though the assumption that an increase of grouting pressure to shorten grouting time has been used in engineering practices for a long time, there is a lack of sufficient supporting theories to verify the assumption. Moreover, there are no existing criteria to quantify the magnitude and degree of impact of fracture deformation on grout flow through fractures. The present paper therefore aims to quantitatively evaluate the dynamic process of fracture deformation and its impact on grout penetrability. Fracture deformation is a dynamic process as both the range of grout penetration and injection pressure are time dependent, so a theoretical pseudo-coupling model is proposed, including an analytical model to determine time varying grouting parameters of two neighboring fractures and a numerical model to assess the associated fracture deformation. Design of Experiment (DOE) and sensitivity analysis are utilized to determine the characteristics of fracture deformation and critical factors affecting its magnitude and distribution. It is found that the apertures, the aperture difference, and the stiffness of the two neighboring fractures are the three most important factors, and a large deformation occurs when both fractures are of small apertures. The ratio of fracture aperture to D95 of cement particle has a significant impact on grout penetrability, whereas the associated impact could be much lower by considering dynamic fracture stiffness