Search Results (37)

Polyethylene storage tanks are widely used for storing water and chemicals due to their lightweight and corrosion-resistant properties. Despite these advantages, their structural performance under seismic conditions remains a concern, mainly because of their low mechanical strength and weak bonding characteristics. In this study, a method of external strengthening using fiber-reinforced polymer (FRP) laminates is proposed and explored. The research involves a combination of laboratory testing on carbon fiber-reinforced polymer (CFRP)-strengthened polyethylene strips and finite element simulations aimed at assessing bond strength, anchorage length, and structural behavior. Results from tensile tests indicate that slippage tends to occur unless the anchorage length exceeds approximately 450 mm. To evaluate surface preparation, grayscale image analysis was used, showing that mechanical sanding increased intensity variation by over 127%, pointing to better bonding potential. Simulation results show that unreinforced tanks under seismic loads display stress levels beyond their elastic limit, along with signs of elephant foot buckling—common in thin-walled cylindrical structures. Applying CFRPs in a full-wrap setup notably reduced these effects. This approach offers a viable alternative to full tank replacement, especially in regions where cost, access, or operational constraints make replacement impractical. The applicability is particularly valuable in seismically active and densely populated areas, where rapid, non-invasive retrofitting is essential. Based on the experimental findings, a simple formula is proposed to estimate the anchorage length required for effective crack repair. Overall, the study demonstrates that CFRP retrofitting, paired with proper surface treatment, can significantly enhance the seismic performance of polyethylene tanks while avoiding costly and disruptive replacement strategies. Full article

Foot and mouth disease virus (FMDV) is a highly pathogenic virus that mainly infects cloven hooved animals, such as pigs. The establishment of a rapid, sensitive and accurate point-of-care detection method is critical for the timely identification and elimination of infected pigs for controlling this disease. In this study, a RT-RAA-CRISPR/Cas13a method was developed for the detection of FMDV serotype O in pigs. Six pairs of RT-RAA primers were designed based on the conserved gene sequence of FMDV serotype O, and the optimal amplification primers and reaction temperatures were screened. The CRISPR-derived RNA (crRNA) was further designed based on the optimal target band sequence and the most efficient crRNA was screened. The results revealed that FMDV-O-F4/R4 was the optimal primer set, and the optimal temperature for the RT-RAA reaction was 37 °C. Moreover, crRNA4 exhibited the strongest detection signal among the six crRNAs. The established RT-RAA-CRISPR/Cas13a method demonstrated high specificity and no cross-reactivity with other common swine pathogens such as Senecavirus A (SVA), porcine reproductive and respiratory virus (PRRSV), porcine epidemic diarrhea virus (PEDV), porcine circovirus type 2 (PCV2), classical swine fever virus (CSFV), and pseudorabies virus (PRV), additionally, it was observed to be highly sensitive, with a detection limit of 19.1 copies/µL. The repeatability of this method was also observed to be good. This method could produce stable fluorescence and exhibited good repeatability when three independent experiments yielded the same results. A validation test using three types of simulated clinical samples (including swab, tissue, and serum samples) revealed a 100% concordance rate. The detection results could be visualized via a fluorescence reader or lateral flow strips (LFSs). Thus, a highly specific and sensitive RT-RAA-CRISPR/Cas13a detection method was developed and is expected to be applied for the rapid detection of FMDV serotype O in situ. Full article

In construction, closely spaced footings cause stress interactions that impact bearing capacity, settlement, and stability. This study experimentally evaluates the role of sheet pile walls (SPWs) in improving the performance of two adjacent strip footings—an existing footing and a newly placed footing—on sandy soil. The influence of SPW penetration depth (L_s) and center-to-center spacing between footings (X) on settlement and bearing resistance under vertical loads was investigated. Experiments were conducted in a large-scale soil tank (330 × 30 cm, depth 210 cm), with X ranging from 300 mm to 1000 mm and SPW lengths varying from 0 mm to 1500 mm. The results show that SPWs significantly enhance foundation performance by reducing settlement and increasing bearing capacity. When L_s/B = 6, the settlement of the new footing (F₁) decreases by 48%, while the existing footing (F₂) sees reductions of 47%, 67%, and 77% at L_s/B = 3, 4, and 5, respectively, under 500 kN/m² stress. The bearing capacity of F1 increases by 53% when X = 300 mm, demonstrating strong interference effects. Conversely, the F₂ settlement increases as X decreases, with a 96% rise at X = 300 mm, but it stabilizes at L_s/B = 5. SPWs also shift failure from general shear to punching shear, modifying soil–structure interaction. These findings highlight the effectiveness of SPWs in mitigating settlement, enhancing load-bearing capacity, and optimizing foundation design in closely spaced footing systems. The results suggest that an SPW length-to-footing width ratio (L_s/B) between 4 and 5 is optimal for minimizing settlement and improving stability, with only a slight difference in effectiveness between these two ratios. Full article

Nipah virus (NiV) is a severe zoonotic pathogen that substantially threatens public health. Pigs are the natural hosts of NiV and can potentially transmit this disease to humans. Establishing a rapid, sensitive, and accurate point-of-care detection method is critical in the timely identification of infected pig herds. In this study, we developed an NiV detection method based on reverse transcription–recombinase polymerase amplification (RT-RAA) and the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 13a (Cas13a) system for the precise detection of NiV. The highly conserved region of the NiV gene was selected as the detection target. We first designed eleven pairs of RT-RAA primers, and the optimal primer combination and reaction temperature were identified on the basis of RT-RAA efficiency. Additionally, the most efficient crRNA sequence was selected on the basis of the fluorescence signal intensity. The results revealed that the optimal reaction temperature for the developed method was 37 °C. The detection limit was as low as 1.565 copies/μL. Specificity testing revealed no cross-reactivity with nucleic acids from six common swine viruses, including Seneca virus A (SVA), foot-and-mouth disease virus (FMDV), classical swine fever virus (CSFV), porcine epidemic diarrhea virus (PEDV), African swine fever virus (ASFV), and pseudorabies virus (PRV). A validation test using simulated clinical samples revealed a 100% concordance rate. The detection results can be visualized via a fluorescence reader or lateral flow strips (LFSs). Compared with conventional detection methods, this RT-RAA-CRISPR/Cas13a-based method is rapid and simple and does not require scientific instruments. Moreover, the reagents can be freeze-dried for storage, eliminating the need for cold-chain transportation. This detection technology provides a convenient and efficient new tool for the point-of-care diagnosis of NiV and for preventing and controlling outbreaks. Full article

In this paper, the numerical study of the ultimate bearing capacity (UBC) of two closely spaced strip footings on granular soil is investigated using the finite element method (FEM) and upper bound limit analysis (UBLA). Although the UBC of two adjacent footings has previously been studied in other experimental and numerical research, in all the previously reported studies, the footings were not allowed to rotate and move horizontally freely. Due to the deformation of the soil medium, two closely spaced footings are subjected to horizontal movements and tilting, even under central vertical loads. When the two adjacent footings are not permitted to rotate and move in the horizontal directions, the unwanted bending moment and horizontal force act on the footings. Indeed, the UBC of two closely spaced rough footings is evaluated under incorrect constraints in earlier research. In the present research, the UBC of two adjacent rough footings is evaluated with and without these incorrect constraints. The key finding of this study is that constraining the horizontal and rotational movement of the foundation artificially increases the UBC, which does not reflect field conditions. When foundations are permitted to rotate and move horizontally, there is no increase in UBC; however, there is an increased risk of differential settlement and structural instability. Full article

This paper analyzes the bearing capacity of two-layered soil medium using finite element (FE) software ABAQUS/CAE 2023. Although geotechnical engineers design foundations for layered soil, majorly current geotechnical studies emphasize single homogenous soil. So, this research has significant novelty as it focuses on layered soil and adds to the current literature. A nonlinear FE model was prepared and analyzed to determine the ultimate bearing capacity of two-layered soil (sandy soil over clayey soil). The Drucker–Prager and Mohr–Coulomb models were used to represent sandy soil and clayey soil layers, respectively. Strip footing material properties were considered isotropic and linearly elastic. This study performed parametric studies to understand the effects of thickness, unit weight, and the modulus of the elasticity of sandy soil on the ultimate soil bearing capacity. Additionally, it also analyzed the effect of the cohesive strength of clayey soil on layered soil bearing capacity. Results showed that an increase in sandy soil layer thickness strengthens the layered soil, and thus, improves the bearing capacity of soil. Increasing the sandy soil layer thickness over footing width (h1/B) ratio from 0.15 to 2.0 improved the ultimate bearing capacities with elastic settlements of 350 mm and 250 mm by 145.62% and 101.66%, respectively. Additionally, for a thicker sandy soil layer, an increase in the unit weight and modulus of the elasticity of sandy soil led to higher ultimate bearing capacity. Furthermore, it was concluded that an increase in clayey soil’s cohesive strength from 20 kPa to 30 kPa resulted in a 24.31% and 3.47% increase in soil bearing capacity for h1/B = 0.15 and h1/B = 2.0, respectively. So, the effect of cohesion is prevalent in the case of a thicker clayey soil layer. Full article

Soil nailing is a prevalent and cost-effective technique employed to reinforce and enhance the stability of precarious natural or cut slopes; however, its application as a primary support system to prevent collapses or cave-ins during foundation excavation could be more frequent. To better understand the behavior of such a support system, this study simulated a full-scale nail-supported excavation for the foundation pit of a 20-story building to examine the effect of placing a strip footing with various combinations of configurations on the crest of the excavation pit. The results are discussed in terms of the nail axial force, wall horizontal deflection, basal heave, and safety factor against sliding. The results show that the footing width and setback distance are the two most significant factors dominating the wall horizontal deflection. This study also reveals that the maximum axial force is closely related to the apparent active earth pressure, which accounts for the presence of a tension crack, at nail depth. Such a finding allows engineers to assess and mitigate the risks of structural failure more effectively and optimize the design of nail-retaining structures. Full article

With the conventional mechanical rotation measurement of joints, only static measurements are possible with the patient at rest. In the future, it would be interesting to carry out dynamic rotation measurements, for example, when walking or participating in sports. Therefore, a measurement method with an elastic polymer-based capacitive measuring system was developed and validated. In our system, the measurement setup was comprised of a capacitive strain gauge made from a polymer, which was connected to a flexible printed circuit board. The electronics integrated into the printed circuit board allowed data acquisition and transmission. As the sensor strip was elongated, it caused a change in the spacing between the strain gauge’s electrodes, leading to a modification in capacitance. Consequently, this alteration in capacitance enabled the measurement of strain. The measurement system was affixed to the knee by adhering the sensor to the skin in alignment with the anterolateral ligament (ALL), allowing the lower part of the sensor (made of silicone) and the circuit board to be in direct contact with the knee’s surface. It is important to note that the sensor should be attached without any prior stretching. To validate the system, an in vivo test was conducted on 10 healthy volunteers. The dorsiflexion of the ankle was set at 2 Nm using a torque meter to eliminate any rotational laxity in the ankle. A strain gauge sensor was affixed to the Gerdii’s tubercle along the course of the anterolateral ligament, just beneath the lateral epicondyle of the thigh. In three successive measurements, the internal rotation of the foot and, consequently, the lower leg was quantified with a 2 Nm torque. The alteration in the stretch mark’s length was then compared to the measured internal rotation angle using the static measuring device. A statistically significant difference between genders emerged in the internal rotation range of the knee (p = 0.003), with female participants displaying a greater range of rotation compared to their male counterparts. The polymer-based capacitive strain gauge exhibited consistent linearity across all measurements, remaining within the sensor’s initial 20% strain range. The comparison between length change and the knee’s internal rotation angle revealed a positive correlation (r = 1, p < 0.01). The current study shows that elastic polymer-based capacitive strain gauges are a reliable instrument for the internal rotation measurement of the knee. This will allow dynamic measurements in the future under many different settings. In addition, significant gender differences in the internal rotation angle were seen. Full article

Geosynthetic-reinforced soil structures are often used to support shallow foundations of various infrastructure systems including bridges, railways, and highways. When such infrastructures are located in seismic areas, their performance is linked to the seismic bearing capacity of the foundation. Various approaches can be used to calculate this quantity such as analytical solutions and advanced numerical models. Building upon a robust upper bound limit analysis, we created a database comprising 732 samples. The database was then used to train and test a model based on a random forest machine learning algorithm. The trained random forest model was used to develop a publicly available web application that can be readily used by researchers and practitioners. The model considers the following input factors: (1) the ratio of the distance of the foundation from the edge and the width of the foundation (D/B), (2) the slope angle (β), (3) the horizontal seismic intensity coefficient (k_h), and (4) the dimensionless geosynthetic factor, which accounts for the tensile strength of the geosynthetic. Leveraging the model developed in this study, we show that the most important features to predict the seismic bearing capacity of strip footings positioned on the crest of geosynthetic-reinforced soil structures are D/B and k_h. Full article

In order to study the influence of tunnel volume loss on adjacent framed buildings with different shallow foundations, this paper carried out physical model experiments with two common types of footings (isolated and strip footings) under different working conditions based on the digital image correlation (DIC) technique. The main finding of the present paper is that the increase in formation loss rate will aggravate the deformation and damage of the structure, and the strip foundation shows stronger integrity and stability compared with the isolated foundation in this process. With the increase in the eccentricity of the frames with respect to the tunnel, the overall tilt and damage degree of structural elements increases first and then decreases for both foundations, reaching the maximum value with the eccentric distance of one multiple of the tunnel diameter. Interestingly, when the isolated footings are located directly above the tunnel, the damage in the inner panels is the most severe and gradually decreases with eccentricity, changing from a sagging mode to a hogging mode for the frame form. While the strip footings always maintain slight hogging, and the trend of the damage degree of panels is similar to that of elements, with the eccentric distance reaching two times the tunnel diameter, the strip foundation structure tends to be stable, while the isolated one still needs attention for its potential possibility of damage in panels. The research results have reference value for the impact assessment of adjacent shallow-foundation framed buildings in subway tunnel construction. Full article

The study of analytical solutions for the bearing capacity of reinforced soil foundations is a very important topic in engineering mathematics. Existing evaluations of the foundation-bearing capacity on reinforced soils are based on dry conditions, while many foundations are located on unsaturated soils in real engineering. In this paper, a new formula for the bearing capacity of reinforced strip footings on unsaturated soils is presented. Two sliding failure mechanisms are constructed based on the position of the reinforcement layer relative to the sliding surface. The distribution of apparent cohesion in the depth direction is calculated by considering the effect of matrix suction. By additionally considering the work conducted by the reinforcement and the contribution of the apparent cohesion, the bearing capacity formula is obtained using the upper bound theorem of limit analysis. The bearing capacity solution is obtained by adopting the sequential quadratic programming (SQP) algorithm. Comparing the results under two failure mechanisms, the optimal bearing capacity and the optimal embedment depth of reinforcement are obtained. The results of this paper are consistent with those of the existing literature. Finally, the effects of reinforcement embedment depth, effective internal friction angle, uniform load, and unsaturated soil parameters on the optimal bearing capacity are investigated through parametric analysis. This paper provides useful recommendations for the engineering application of reinforced strip footings on unsaturated soils. Full article

The aim of this study is to investigate the bearing capacity-settlement behavior of strip footing settling on sand soil randomly reinforced with glass fiber, basalt fiber, macromesh fiber, and four different hybrid fiber additives in which these fibers are used together. Model tests were carried out in the laboratory on the strip footing and placed on the unreinforced and reinforced sand with different fibers. In the study, model tests were carried out on seven types of randomly reinforced soils by using glass, basalt, macrame, and mixtures of these fibers as reinforcement. In the model tests, two different fiber contents, 1% and 2%, and two different fiber lengths, 24 mm and 48 mm, were used. Tests were carried out with Dr = 30% and 50% relative density, and reinforcement depths 1B, 2B, and 3B were selected. In addition, the photographs taken during the test were analyzed with the particle image velocimetry (PIV) method and the displacements on the soil were examined. As a result of the reinforced and unreinforced model tests, the highest ultimate bearing capacity was measured as 680 kPa from the tests with Dr = 50% relative density, 48 mm length, 2% contents, and 3B depth macromesh fiber reinforced. In hybrid fibers, the highest ultimate bearing capacity was measured as 495 kPa, with Dr = 50% relative density, 48 mm length, 2% contents, and 2D depth micromesh and basalt fiber-reinforced tests. In the reinforced tests, it was concluded that the most effective fiber on bearing capacity is macromesh fiber. It can be seen that in the PIV analysis, as the fiber additive increased, the settlements made by the foundation decreased under the same pressure. It has also been observed that adding reinforcement to the soil transfers the stresses occurring in the soil to a wider area. Full article

The evaluation of the bearing capacity of strip footings generally assumes that the soil is either dry or fully saturated, which contradicts the actual condition in nature where the soil is often in a partially saturated state. Furthermore, infiltration has a significant impact on the shear strength of the soil. Following the upper bound theory of the limit analysis, this article provides a theoretical framework for assessing the bearing capacity under transient flow with linear variation in infiltration intensity for the first time. Firstly, the closed form of suction stress under linear transient infiltration is derived using Laplace transform and introduced into the Mohr–Coulomb criterion. A discrete failure mechanism with fewer variables and higher accuracy is provided to ensure kinematic admissibility. The upper bound solution for bearing capacity is obtained by solving the power balance equation. The present results are compared with results from the published literature and the finite element, confirming the validity and superiority of the theoretical framework provided. A parametric analysis is also conducted on three hypothetical soil types (fine sand, silt, and clay), and the results show that unsaturated transient infiltration has a positive influence on increasing the foundation bearing capacity. The magnitude of the influence is comprehensively controlled by factors such as soil type, saturated hydraulic conductivity, infiltration intensity, infiltration time, and water table depth. The increase in bearing capacity due to unsaturated transient infiltration can be incorporated into Terzaghi’s equation as a separate component presented in tabular form for engineering design purposes. Full article

Due to terrain and transportation constraints, some open cast mines have to choose a weak basement as their tailings dumping grounds. Therefore, ensuring the bearing capacity and slope stability of dumping grounds on the weak basement is of great significance for the production capacity and economic benefits of open cast mining. To ensure the safety of surrounding facilities and the normal production of open cast mines, the bearing capacity of the dumping ground of a certain open cast mine was calculated using the oblique strip method and verified by numerical simulation. On this basis, the potential failure mode of the dumping ground base was analyzed, and the ultimate bearing capacity of the dumping ground under current conditions was calculated. The results are as follows: (1) The ultimate bearing capacity of the current dumping ground base is 3781 kPa, and the failure mode of the base is overall shear sliding along the base of the dumping ground. (2) When the slope foot increases from 12° to 18°, the stability coefficient and critical bearing capacity coefficient of the slope base decrease by about 21% and 46%, respectively. The slope angle has a greater impact on the bearing capacity of the base, and the height of the slope body has a relatively small impact, with almost no width effect. (3) Compared with the classic Terzaghi method and Prandtl method, the ultimate bearing capacity of the dumping ground base determined using the oblique strip method proposed in this paper is closer to the numerical simulation results, with an error of no more than 5%, a consistent critical sliding surface, and results that are relatively consistent with the engineering practice monitoring of the surface uplift part. The calculation results of the bearing capacity of the weak basement of open cast mine dumping grounds using the oblique strip method are reliable. Full article

In engineering mathematics, the unsaturated nature of soil has a significant impact on the seismic bearing capacity solution. However, it has generally been neglected in the published literature to date. Based on the kinematic approach of limit analysis, the present study proposes a method for calculating the bearing capacity of shallow strip footings located in unsaturated soils, taking four common types of soils as examples. The modified pseudo-dynamic (MPD) approach is used to calculate the seismic forces varying with time and space, and the layerwise summation method is used to derive the power generated by the seismic forces. In the calculation of internal energy dissipation, this paper introduces the effective stress based on the suction stress to derive the cohesion expression at different depths. The analytical formula of bearing capacity is obtained by the principle of virtual work, and its value is optimized by the Sequential Quadratic Programming (SQP) algorithm. In order to verify the validity of the proposed method, the present results are compared with the solutions published so far and a good agreement is obtained. Finally, a parametric study is performed to investigate the influence of different types of parameters on the bearing capacity. Full article