Search Results (12)

As the core component for fracturing plug anchoring, dissolvable ball seat (DBS) slip performance directly determines the success of fracturing operations. However, frequent failures, such as tooth structural fractures, casing damage, and the slip breaking off entirely, compromise DBS reliability during high-pressure fracturing. This study investigates DBS slip anchoring performance through finite element analysis (FEA), anchoring performance tests, and structural optimization. We established a comprehensive safety and performance assessment framework incorporating strength criteria, peak contact pressure, and anchoring uniformity. Comparative stress analysis of nail-type versus block-type slip systems revealed superior performance in block-type configurations, demonstrating more uniform slip–casing interfacial stress distribution. To further enhance the anchoring performance of the block-type slip, a structural parameter analysis was conducted to identify critical factors influencing anchoring capability, with tooth apex angle and inclination angle determined as key parameters. The influence laws of these parameters on anchoring performance were systematically investigated. Subsequently, a multi-parameter optimization methodology was employed to optimize the structural configuration of the block-type slip. The optimization results revealed that an optimal slip tooth apex angle of 80° or 85° and an inclination angle of 70° enhance the safety and anchoring reliability of the dissolvable ball seat slip while providing a theoretical framework for future slip structure design improvements. At present, the new structure of the soluble ball seat structure proposed in this paper has been successfully applied in some oil fields. Field tests show that the anchoring efficiency has been significantly improved. This research not only provides a theoretical framework for the design of sliding structures, but also offers reliable technical support for the efficient development of deep oil and gas resources. Full article

To address poor film pickup, incomplete soil–film separation, and high soil content in conventional residual film recovery machines, this study designed a belt-tooth type residual film recovery machine. Its core component integrates flexible belts with nail-teeth, providing both overload protection and efficient conveying. EDEM simulations compared film pickup performance across tooth profiles, identifying an optimal structure. Based on the kinematics and mechanical properties of residual film, a film removal mechanism and packing device were designed, incorporating partitioned packing belts to reduce soil content rate in the collected film. Using Box–Behnken experimental design, response surface methodology analyzed the effects of machine forward speed, film-lifting tooth penetration depth, and pickup belt inclination angle. Key findings show: forward speed, belt angle, and tooth depth (descending order) primarily influence recovery rate; while tooth depth, belt angle, and forward speed primarily affect soil content rate. Multi-objective optimization in Design-Expert determined optimal parameters: 5.2 km/h speed, 44 mm tooth depth, and 75° belt angle. Field validation achieved a 90.15% recovery rate and 5.86% soil content rate. Relative errors below 2.73% confirmed the regression model’s reliability. Compared with common models, the recovery rate has increased slightly, while the soil content rate has decreased by more than 4%, meeting the technical requirements for resource recovery of residual plastic film. Full article

The advancement of sustainable infrastructure relies on innovative design and computational modeling techniques to optimize excavation stability. This study introduces a novel approach to soil nail configuration optimization using finite element analysis (FEA) with Plaxis software (V22). Various soil nail parameters—including length, angle, and spacing—were analyzed to achieve the most efficient stabilization while minimizing costs. Results indicate that a 10-degree nail inclination from the horizontal provides an optimal balance between tensile and shear forces, reducing deformation (18.12 mm at 1 m spacing) and enhancing the safety factor (1.52). Increasing nail length significantly improves stability, but with diminishing returns beyond a threshold, while nail diameter shows minimal impact. Soil type also plays a crucial role, with coarse-grained soils (friction angle 35°) demonstrating superior performance compared to fine-grained soils (friction angle 23°). This research contributes to the field of computational modeling and intelligent design by integrating advanced simulation techniques for geotechnical stability analysis, providing an innovative and data-driven framework for parametric evaluation of soil nail configurations. Full article

Used for soil and weathered rocks, soil nails are rigid reinforcements positioned at certain angles on the ground to provide slope stability. A rigid reinforcement element placed in a well filled with cement grout mix after completing drilling will generate adherence stress between the grout-mixed nail bar and soil. Due to this stress, load is transferred to the soil along the soil–grout interaction surface. In the case discussed herein, the slope at the parcel border needed to be made steeper in order to accommodate the construction of a facility in the Taşkısığı region of Sakarya province. Soil-nailed walls, which are inexpensive and suitable for weathered rocks, were needed as a support system because the slope was too steep to support itself. Support system performance was measured using two inclinometers and two soil nail pull-out tests conducted on different sections observed during and after construction. Contrary to the design-phase prediction, it was determined that the stresses started to dampen in the region closer to the slope-facing zone. Field measurement data and numerical analysis revealed that higher parameters than necessary were selected. In this context, sensitivity and parameter analyses were carried out using the Hoek–Brown constitutive model. The GSI value was re-evaluated and found to be compatible with the observation results obtained from the field performance. Since the retaining wall performance observed was higher than expected, geometric parametric analysis of the structural elements was performed; high safety coefficients were found across variations. The effects of the inclination of the slope, nail length, nail spacing, and nail slope design parameters on the safety coefficient and horizontal displacement were examined. The optimal design suggested nail lengths of 4.00 m, a spacing of 1.60 m, and slopes of 20°. It was discovered that the effect of the inclination degree of the slope on the safety coefficient was lower than expected. The results revealed that a more economical design with a similar safety factor can be obtained by shortening the lengths of the nails. Full article

Timber–concrete composite (TCC) systems present a viable alternative to conventional timber or reinforced concrete systems. TCC leverages the advantages of both materials, resulting in an enhanced composite structure. Historically, traditional mechanical connectors such as nails, bolts, and dowels have been used in TCC systems to join timber and concrete components. However, these connectors often fall short in providing sufficient load transfer efficiency. Therefore, the use of screws and, more recently, inclined screws in TCC systems has increased due to their enhanced load transfer efficiency and greater stiffness compared to traditional connections. This review paper consolidates findings from contemporary experimental studies and analytical models, examining the influence of factors such as screw type and inclination angle on the performance of TCC systems for both connection and beam specimens in ultimate and serviceability limit states. Key issues addressed include the shear strength, stiffness, and long-term behaviour of the connection type. By offering a comprehensive synthesis of existing knowledge, this paper aims to inform design practices and contribute to the development of more resilient and efficient TCC systems, supporting their increased adoption in sustainable construction. Full article

Nail biting (NB) is a repetitive and uncontrolled parafunctional activity that can affect oral health by altering tooth shape and intraoral position. Nowadays, there is not enough scientific evidence about the impact of NB on teeth; therefore, this study aimed to evaluate the effects of NB on the length, width and inclination of upper central incisors. This retrospective study involved 76 patients, 40 males and 36 females, with a mean age of 10.6 ± 0.3 years. Digital scans of the maxillary arch of each patient were recorded. Next, the length, width and inclination of upper central incisors used and not used for NB were measured. Finally, data were analysed with a paired t-test. Statistical analysis showed statistically significant differences in the length and inclination of upper central incisors used for NB compared with those of upper central incisors not used for NB, while the width did not show a significant difference. There were relevant changes in upper central incisors subjected to NB, demonstrating that NB impairs the shape, morphology and inclination of teeth. Therefore, because of the potentially negative consequences of NB, it is recommended that NB not be underestimated. Full article

The purpose of this research is to compare the bending behaviour of non-glue-laminated timber beams and glulams by full-scale four-point bending tests. The focus is on the non-glue beams laminated by different materials or techniques and then to determine their bending stiffness and failure modes. The laminating efficiency of various materials or techniques is underlined. The manufacturing process concerning non-glue-laminated timber beams has to be determined. As structural elements with large dimensions, such components require adaptable laminating and producing techniques. While the beams composed of wooden dowels refer to the dowel-laminated timber (DLT), those made of self-tapping screws (STSs) can be simply related to nail-laminated timber (NLT) products. Then, a full-scale four-point bending test was carried out to appraise 26 laminated beams, including non-glue- and glue-laminated timber. The results of the test demonstrated that the material, the spacing and the angle of the transversal fasteners significantly influence bending behaviour. The bending stiffness of the beams laminated by STSs was about 7.86% higher than the value of the beams with wooden dowels, although the tendency of each pair of beams did not remain convergent. Reducing the interval of the fasteners can considerably increase the bending stiffness of the beams. Fasteners inserted at 45 degrees, or in a so-called V-type pattern, contribute to improving bending stiffness, and both wooden dowels and STSs reveal the same tendency. At this angle, STSs demonstrate better laminating efficiency than wooden dowels. The STS beams’ bending stiffness was about 48.6% of that determined for glulams. On the contrary, in beams with 135-degree fasteners, or, namely, an A-type pattern, inserted fasteners possessed lower bending stiffness than in those with 90-degree fasteners. In addition to the considerable bending stiffness, the STS beams revealed a stable response as far as their load-deflection curves were concerned. A comparison of experimental and theoretical results contributes to verifying the feasibility as well as the weakness of two analytic methods. The predicting capacity of the associated equations needs to be improved, particularly for the withdrawal resistance and connecting effect of inclined STSs. Full article

The finite element technique has been accepted as a tool for modeling geotechnical complex processes. In this study, finite element (FE) modeling of various stages of the soil-nailing process, i.e., construction stages and overburden pressure stages, is carried out considering different soil parameters, simulating with in-house developed laboratory models. The soil-nailing process built in laboratory models is idealized as a plain strain problem and modeled in PLAXIS software. The laboratory models of the soil-nailing process consist of a Perspex sheet box containing a sandy soil slope, a Perspex sheet facing, steel bars as reinforcement and a steel plate as foundation. The stress–strain relationship of the sand is represented by a Hardening-Soil model. The interface at the soil and nail is described by the Coulomb friction model. The behavior of the soil-nailing process, during the construction stage and under varying overburden pressure and varying soil density, are investigated in terms of displacements of slope and stress conditions in slope soil mass. The slope displacements and stress conditions in slope soil mass are all well presented by the FE modeling and compared with laboratory model test data. The sensitivity analysis of the laboratory models’ dimensions is carried out by three-dimensional modeling of the nailed-soil slope. It can be concluded that the developed finite element model has the potential to simulate the performance of a field nailed-soil slope during construction and working stages and could provide guidance for the construction/maintenance of soil-nailed cut slopes in granular soils/weathered rocks. Full article

This study focuses on the stability analysis of slopes reinforced by soil nailing. The effects of slope geometry and nail parameters on slope stability are investigated using PLAXIS 2D. Four different slope angles and three different backslope angles are considered for assessing the effect of slope geometry on the stability of a nailed slope. The factor of safety (FS) was found to decrease with the increasing values of the slope angle as well as the backslope angle. The influence of different nail parameters (nail inclination, nail length, and nail spacing) was also investigated. With the increase in nail inclination, FS was found to increase initially and thereafter, reaching a peak value followed by a drop in FS. The optimum nail inclination was found between 0 and 25° at a horizontal angle, depending on the different slope geometries, which is evident from observation of the slip surface as well. With the increase of nail length, FS increases; however, the increase was small after L/H (length of nail/height of slope) reached a value of 0.9. Moreover, increasing the length of the nail was found to be effective in reducing the lateral movement of the slope. The maximum nail forces are observed in the bottom-most row of nails and increase with the depth. The inclusion of soil nailing with optimum nail parameters can increase FS by 29–75% depending on the slope geometry, signifying the effectiveness of nailing. Full article

The earth nailing system is a ground improvement technique used to stabilize earth slopes. The behavior of the earth nailing system is dependent on soil and nailing characteristics, such as the spacing between nails, the orientation, length, and method of installation of nails, soil properties, slope height and angle, and surcharge loading, among others. In the present study, a three-dimensional physical model was built to simulate a soil nailed slope with a model scale of 1:10 with various soil nail characteristics. The simulated models consist of Perspex strips as facing and steel bars as a reinforcing system to stabilize the soil slope. Sand beds in the model were formed, using a sand raining system. The performance of nailed soil slope models under three important nails characteristics, i.e., length, spacing and orientation, with varying surcharge loading were studied. It was observed that there is a reduction in the lateral movement of slope and footing settlements with an increase in length. It was found that the slope face horizontal pressure is non-linear with different nail characteristics. The increase in length and inclination of the soil nails decreased the vertical, horizontal stress and footing settlement, while the increase in spacing of the nails increased the vertical and horizontal stress behind the soil mass. Full article

Today, the extrusion-based 3D printing of concrete is a potential breakthrough technology for the construction industry. It is expected that 3D printing will reduce the cost of construction of civil engineering structures (removal of formwork) and lead to a significant reduction in time and improve working environment conditions. Following the use of this additive manufacturing layer-wise process, it is required to change the way concrete structures are designed and reinforced, especially for the parts of the structure under tension loads. Indeed, the extrusion-based concrete 3D printing process does not allow for the production of conventional reinforced concrete, and there is a need to develop other ways of compensating for the low mechanical performances of concrete, particularly in tension. In this study, the reinforcement of printed structures by using steel nails through the deposited layers of fresh concrete was investigated. Additionally, three-layer and 10-layer samples were reinforced with nails with varying inclination and spacing. The results show that inclined nails can be used to provide a flexural strengthening of the printing material in different directions. Full article

In special geology conditions such as silt-soil, foundation pits are prone to instability and severe deformation. In this paper, a composite soil nailing structure was studied and its effect on a silt-soil symmetrical foundation pit investigated. The factors affecting the stability of the pit as well as its deformation characteristics were also explored. The results show that excavation depth of the foundation pit has a significant impact on its stability. The soil outside the foundation pit is in the form of a parabola, and the uplift of the soil mainly occurs at the bottom. The horizontal displacement of soil on the side wall of the foundation pit presents a “bulk belly” form. In addition, the axial force of soil nails is larger in the middle part, and smaller at both ends in the shape of a spindle. Moreover, the horizontal displacement is positively correlated with the inclination and spacing of the soil nails, but negatively correlated with the diameter and depth of the mixing pile inlay. Furthermore, the inclination and spacing of the soil nails, the diameter, and embedded depth of the mixing pile have their own critical values for stability of the foundation pit. Specifically, in this paper, with respect to soil nails, inclination should be below 30° and prestress value should not exceed 20 kN. With respect to the mixing pile, the diameter should be less than 1.5 m; when the embedded depth of the mixing pile exceeds the critical depth, the limiting effect of the mixing pile on horizontal displacement is not significant. This research provides important takeaways for the design of a composite soil nailing structure for symmetrical foundation pits. Full article