High Bearing Capacity Research Articles

Mapping the environmental impacts from land subsidence hazard in Pekalongan City and its correlation with the subsurface condition

Land subsidence in Pekalongan city has affected almost the entire municipality for at least ten years. Land subsidence has occurred in almost all Pekalongan city areas at 2-12 cm/year rates. The direct and indirect environmental impacts of land subsidence are enormous. We aim to map the environmental impacts of land subsidence in Pekalongan city and evaluate the severity of the impacts with the subsurface condition of the affected area. We employed site investigation using resistivity and CPTu soundings at representative sites to reveal the subsurface soils and site survey to map the environmental impacts. Resistivity measurements using a Schlumberger array were carried out at 24 sites, along with 12 CPTu measurements up to 30 m deep. Results show that the subsurface condition up to the depth of 30 m consists of alluvial sediment of clay, silt, and organic soils intercalated with lenses of sand. The alluvial sediment in the southern part is dominated by sandy soils and has a higher stiffness with cone resistance of 1-2 MPa and a friction ratio of 50-200 kPa. The subsurface soils in the northern part are dominated by clay, silt, and organic soils with low cone tip resistance of <0.5- 1 MPa, and friction ratio of <0.25-100 kPa. These values indicate that the sandy soils in the southern part are more compact and have higher bearing capacity than the soft, fine-grained soils in the northern area. The visible impacts of land subsidence include flood and inundation, settlement of buildings and roads, and cracks in houses and infrastructure. The severity of impacts worsens from South to North of the city. This condition is related to the subsurface stratification and engineering properties, where lower bearing capacity occurs in the north.

Axial Compression Behaviour and Modelling of Pultruded Basalt-Fibre-Reinforced Polymer (BFRP) Tubes

Laminated fibre-reinforced polymer (FRP) tubes are increasingly used as compression members in large-span spatial structures due to their high bearing capacity, corrosion resistance, and superior stability compared to high-strength steel pipes. In this study, axial compression tests were conducted on slender BFRP tubes to evaluate their compression characteristics as compression members. The results indicated that BFRP tubes exhibited three distinct failure modes, namely local failure, critical failure, and buckling failure. Overall, buckling was identified as the primary mode of failure under compression. The stress–strain curves of BFRP tubes were characterized by three stages, including elastic, elastic-plastic, and plastic stages. To enable design-oriented approaches, two three-stage theoretical models for BFRP tubes were developed through experimental data analysis. The models predicted the stress–strain curves and the load-lateral deflection curves, taking into account the post-peak softening behaviour of the stress–strain curves. Comparisons between the test results and the predictions calculated using the proposed models indicated that they were in good agreement.

Hysteresis performance of section steel reinforced concrete-filled rectangular stainless steel tubular columns

Due to high bearing capacity and excellent seismic performance, the section steel reinforced concrete-filled rectangular steel tube has been widely applied in engineering. The application of stainless steel for outer steel tube can improve the durability performance of members. In this study, ABAQUS software was used to perform nonlinear seismic analysis on section steel reinforced concrete-filled rectangular stainless steel tubular columns, and the numerical model was validated against experimental data. The mechanism and parametric study of the hysteresis performance were conducted. These parameters mainly include: concrete strength, strength of stainless steel, strength of section steel, steel ratio of stainless steel tube, steel ratio of section steel, axial compression ratio, and slenderness ratio. The analysis results showed that: increasing the strength of stainless steel tube and concrete can significantly improve the bearing capacity of members, but the strength of section steel has little effect; the bearing capacity decreases with the increasing slenderness ratio; when the axial compression ratio is smaller than 0.4, increasing axial compression can improve the bearing capacity. The strength of each material shows little influence on the shape of load–displacement skeleton; the axial compression ratio presents high effect on the shape of descending stage of curve, and the larger the axial compression ratio, the steeper the descending stage; the slenderness shows high influence on curve shape, and the larger the slenderness, the less the elastic stiffness, and the more gentle the descending stage of curve. Finally, a simplified load–displacement hysteretic model was proposed, which exhibits good agreement with finite element numerical analysis.

Optimization Analysis of Key Technologies of Super High-Rise Buildings with Soft Soil Foundation

The frequency of super high-rise buildings has gradually increased in larger cities. Compared with ordinary buildings, super high-rise buildings involve more difficult technologies of construction. Soft soil foundation is one of the unfavorable foundation types for engineering construction because of its high sensitivity and low bearing capacity. Therefore, the combination of super high-rise buildings and soft soil foundations will greatly increase the insecurity of the project. Although related methods of soft soil treatments have been proposed and optimized in recent years, there is still a lack of targeted construction methods combing for super high-rise buildings, which is of vital significance to improve the safety and efficiency of future construction projects. Based on the case analysis of Jinmao Tower, Shanghai World Financial Center and Shanghai Tower in the Lujiazui zone, this paper summarizes the optimization of key technologies of super high-rise buildings under the background of soft soil foundation. The author hopes to provide a clear reference for future projects by systematically sorting out the construction projects in this typical area.

Research on Dynamic Pile-Driving Formula Parameters and Driving Feasibility of Extra-Long PHC Pipe Piles

Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of extra-long PHC pipe piles with a length of more than 50 m is increasing. However, there are few studies on the drivability and hammering criteria of extra-long PHC piles. To analyze the drivability of extra-long piles and predict their bearing capacity, in this paper, high-strain dynamic tests were carried out on 14 test sections with the pile foundation of Temburong Bridge in Brunei as the research background. The hammer stop control criteria calculated according to the Hiley formula would lead to excessive hammering. Three types of damage occurred during construction: pile shaft breakage, weld tearing, and pile head breakage. The weight and drop height of the piling hammer selected for this project were appropriate, and the extra-long test piles can be hammered to the design depth. The values of Cp (Compression of the pile) and n (the efficiency of the blow) were fitted based on the dynamic test data, which provided a more accurate reference for the selection of subsequent piling parameters of the project. It provides a more accurate calculation method for predicting the bearing capacity of extra-long PHC piles and provides control criteria for pile stopping and a scientific basis for their design and construction.

Sustainable geopolymerization approach to stabilize sabkha soil

Sabkha soils, which predominately exist in arid/semi-arid climate zones worldwide, have raised considerable concerns because of their high compressibility and low bearing capacity. This study aimed to assess the feasibility of stabilizing saline sabkha soil through geopolymer treatment using environment-friendly materials. Untreated and treated specimens were characterized using standard proctor compaction, direct shear, and unconfined compressive strength (UCS) tests, field-emission scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The effects of alkaline activator molarity, fly ash concentration, and curing period were investigated. ANOVA and response surface method were utilized to assess the influence of the investigated variables on the produced UCS data set. Results revealed that the enhanced UCS of the geopolymer-treated specimens was highly influenced by the molarity of NaOH. In addition, the alkaline activation of sabkha soil incorporating fly ash had higher UCS and shear strength than the untreated and Ordinary Portland cement (OPC) treated specimens.

A Novel Rectangular-Section Combined Beam of Welded Thin-Walled H-Shape Steel/Camphor Pine Wood: The Bending Performance Study

At present, the development of green building materials is imminent. Traditional wood structures show low strength and are easy to crack. Steel structures are also prone to instability. A novel rectangular-section composite beam from the welded thin-walled H-shape steel/camphor pine was proposed in this work. The force deformation, section strain distribution law, and damage mechanism of the combined beam were studied to optimize the composite beam design, clarify the stress characteristics, present a more reasonable and more efficient cross-section design, and promote green and environmental protection techniques. Furthermore, the effect of different factors such as steel yield strength, H-type steel web thickness, H-type steel web height, H-type steel flange thickness, H-type steel upper flange covered-board thickness, and combined beam width was investigated. The ABAQUS simulation with the finite element software was also performed and was verified through empirical experiments. According to the results: (1) the damage process of the composite beam was divided into three steps, namely elastic stage, elastic–plastic step, and destruction stage, and the cross-middle section strain met the flat section assumption; (2) additionally, the bond connection was reliable, the two deformations were consistent, and the effect of the combination was significant. The study of the main factors showed that an increase in the yield strength, the H-type steel web height, the steel H-beam upper flange thickness, and the combined beam width caused a significant enhancement in the bending bearing capacity. The combined beam led to high bending stiffness, high bending bearing capacity, and good ductility under bending.

Expansion-type oil-based Leak-proof and Plugging Drilling Fluid System

Drilling fluid, as an essential part of the drilling process, directly affects the efficiency and safety of drilling. The expansion-type oil-based leak-proof and plugging drilling fluid system is a new type of drilling fluid with advantages such as leak-proof and plugging, good permeability, and high bearing capacity, and has become a hot topic in drilling fluid research. This paper will provide a detailed introduction to the composition, performance, and application of the expansion-type oil-based leak-proof and plugging drilling fluid system.

An integrated load-bearing and vibration-isolation supporter with decorated metamaterial absorbers

Vibration sources such as power units transmit vibration and load to equipment via supporters, aggravating equipment vibration and radiating noise to the environment. Therefore, a supporter is a necessary path for vibration transmission, and reducing its vibration transmission capability is essential for attenuating equipment vibration and noise. To overcome the challenges presented by the inability of traditional supporters to conciliate contradictions between high-bearing capacity and vibration-isolation performance, this paper proposes an integrated load-bearing, vibration-isolation design by embedding metamaterial absorbers in the supporter. Arranging absorbers on the vibration transmission path suppresses vibration transmission in a wide frequency band without affecting the bearing capacity and realizes the function of replacing isolation with absorption. The gradient parallel, multi-layered design of the absorbers effectively extends the vibration attenuation bandwidth, further improving its vibration attenuation capacity. The metamaterial units could reduce additional weight for structural vibration suppression due to their sub-wavelength dimensions and lightweight characteristics. The vibration-absorbing units can be embedded in the cavities of hollow support structures or arranged as an additional component in the external spaces of non-hollow support structures, making them broadly applicable. The design of integrated load-bearing, vibration-isolation supporters with decorated metamaterial absorbers helps attenuate and reduce equipment noise, providing vital engineering application value.

Mechanical response and energy absorption of bridge block with negative Poisson's ratio

A new negative Poisson's ratio (NPR) block is proposed as girder falling restrainer for bridge structures, which is anticipated to have high energy absorption, high bearing capacity and intensified stiffness inherited the advantages of negative Poisson's ratio structure. The monotone loading test and the FE simulation are employed to investigate the deflection, the load-displacement response, the energy absorption of the block. The sensitivity of the block to the critical geometric parameters is revealed. The FE simulation is also employed to investigate the response of honeycomb NPR blocks. The monotone loading experiment shows that the proposed monomer NPR block has a three-step deformation process and consequently three plateau stages. The stiffness and the plateau load are small in the initial stage but can be significantly increased without significant oscillations in the following stages. The transitional displacements of the block are affected mainly by the folded angle and the length of the steel plates in the NPR monomer while the plateau loads are affected mainly by the thickness and the length of the plates. The total energy absorption of the NPR monomer in the block is more sensitive to the plateau load. The layer of the honeycomb affects mainly the transitional displacement of honeycomb NPR blocks. Cell number in each layer affects both the plateau loads and the transitional displacements.

The Effects of Branch Spacing and Number on the Uplift Bearing Capacity of a New Squeezed Multiple-Branch Pile: A Numerical Simulation Analysis

The squeezed multiple-branch pile is a variable section pile that was built by adding a bearing branch cavity to a constant section pile using expansion and extrusion equipment. It is widely used in engineering practice for its high bearing capacity, small settlement deformation, high economic benefits, strong adaptability, and simple pile forming process. In this paper, a new type of squeezed multiple-branch pile is proposed and its forming tool is invented. The forming tool of the pile has applied for an invention patent and is authorized by the China National Intellectual Property Administration. Multiple groups of comparison models of the new squeezed multiple-branch piles are established by using FLAC3D numerical simulation software to investigate the influence of the number and spacing of branches on the bearing mechanism in response to uplift load. The results indicated that the number and spacing of branches have a significant effect on the uplift bearing capacity, load–displacement curves, side friction resistance, and stress distribution law in the new pile and soil around the pile. The suitable number and spacing of branches maximize the uplift bearing capacity and minimize the settlement of a single pile.

Research on uplift mechanism of screw pile

This paper uses numerical simulation software to study the bearing characteristics of screw pile with pitch after installation. The selected soil is single layer sandy soil, and the blade is buried in deep burial mode. Based on the numerical simulation results, the vertical bearing characteristics of single spiral pile and ordinary bladeless pile are compared, and the excellent compression and pull-out characteristics of spiral pile are revealed. Then, the influences of different pitch sizes, blade diameters, tilt angles, blade numbers and blade spacing on spiral single pile were compared and analyzed. The results show that single screw pile has higher bearing capacity and bearing efficiency. The vertical bearing capacity of single inclined screw pile has no obvious improvement compared with that of straight pile.

Residual Deformation-Based Performance Evaluation Method for CFST Piers Subjected to Vehicle Collision

Concrete-filled steel tubular (CFST) piers have been applied in bridge structures due to their high bearing capacity, good ductility, and light weight. During their service life, CFST piers may suffer vehicle collision. Nevertheless, there is still a lack of a performance evaluation method for CFST piers subjected to vehicle impact. Therefore, this paper presents a residual deformation-based method to evaluate the performance of CFST piers under truck impact. Before that, a numerical model was developed to simulate responses of CFST piers under truck collision and validated by reported impact tests. Then, the performance levels of 6- and 12-m high CFST piers under 20 and 40 ton and 60, 100, and 140 km/h truck collisions were numerically investigated. Afterwards, a residual deformation-based performance evaluation method was proposed based on the numerical investigations. In this method, the ratio of the residual lateral deflection at the mid-height to half of the pier height was first selected as the evaluation index. Then, threshold values of the evaluation index at different performance levels were determined. Finally, an analytical model for the evaluation index was developed. Comparisons indicate that the analytical performance levels are in good agreement with the numerical results. The proposed residual deformation-based performance evaluation method can be used for design and accident analysis of CFST piers subjected to truck collision.

Assembled mechanical metamaterials with transformable shape and auxeticity

Fabricating auxetic metamaterials via an assembling process is a novel and economic method. In this work, an assembled structure that could realize the conversion of positive and negative Poisson’s ratio by changing the length of the connection plates was proposed. Two different honeycomb structures of the assembled re-entrant honeycomb (ARH) and assembled hexagonal honeycomb (AHH) were designed, manufactured and studied numerically and experimentally. Dimensions of the two assembled honeycomb structures are consistent. The nominal stress–strain curves of the two assembled honeycombs have similar initial peak stresses, but the assembled re-entrant honeycomb has a higher bearing capacity and shorter stress plateau. Subsequently, the mechanical properties of ARH were studied by changing the three parameters of corrugated plates. Besides, the energy absorption and specific energy absorption of the assembled re-entrant honeycomb were investigated through the numerical method. Finally, the assembled honeycomb structure with the suitable parameter was determined. Tunable mechanical properties of the assembled auxetic structures can be obtained by varying the length of the connection plates. This strategy of assembly can reduce the costs of manufacturing and improve transportation efficiency. The proposed assembled structures are promising in civil and protective engineering.

Dynamic behavior of concrete-filled steel tube cantilever columns stiffened with encased carbon fiber reinforced plastic profile subjected to lateral impact load

The impact behavior of building and bridge structures is already a growing concern due to the frequent occurrence of vehicle collision accidents. Concrete-filled square steel tube stiffened with encased I-shaped carbon fiber reinforced plastic profile (CFST-CFRP) is suitable for building and bridge structures due to its high bearing capacity and small section size. Thus, this study experimentally and numerically presents the dynamic responses for CFST-CFRP columns under lateral impact to evaluate their impact resistance. Firstly, three CFST-CFRP columns and one CFST column were tested in a rigid vehicle impact device, with variations in impact velocity, impact type, impact impulse of the rigid vehicle, and CFRP profile. The impact force-displacement curve and failure mode of CFST-CFRP columns were obtained. Additionally, finite element analysis (FEA) models were built by ABAQUS and verified against tested results. Then, the working mechanisms of CSFT-CFRP columns under impact load were further revealed in-depth by analyzing displacement, impact force, inertia force, bending moment, shear force, and dissipated energy. Based on the working mechanisms, the effect of the CFRP profile on the dynamic response of CFST-CFRP member subject to different parameters was discussed. The results indicated that all the specimens fail at the support. With the additional CFRP profile in the CFST column, the failure pattern of the steel tube was transformed from fracture to local buckling. CFRP profiles enhance the impact resistance of CFST columns (incremented by 17%), and the increasing ratio rises with the decreasing steel ratio and steel strength of members. Steel tubes can share 72% and 78% of energy absorption and bending moment, which is the main impact-resistant component. For this study, valuable experimental data can be supplied for CFST-CFRP columns subjected to vehicle collision. Meanwhile, a theoretical reference for impact resistance design in the future is also provided.

A Field Study Implementing New Monitoring Technology for Roof Caving and Systematic Monitoring for Gob-Side Entry Retaining via Roof Cutting in Underground Coal Mining

The longwall mining method with gob-side entry retaining via roof cutting is a new underground coal mining method which has the characteristics of a high resource recovery ratio and environmental friendliness. Due to the complexity of this method, the research method of case-based dynamic on-site monitoring, analysis, adjustment, and optimization is usually adopted. Based on a roadway retaining via roof cutting project, in addition to the traditional indirect monitoring method of hydraulic support pressure, this study innovatively establishes a direct monitoring method for roof caving by monitoring the gangue pressure in the goaf, which provides data for the roof cutting effect and offers a new method for studying the overlying strata movement. In the project, a comprehensive monitoring and analysis system was established, including gangue pressure, cable bolt stress, bracket pressure, roadway deformation, and roof separation, which was used to dynamically analyze the effect of roof cutting and optimize the support design. The results show that the pressure of the hydraulic support close to the roof cutting is low, indicating that roof cutting is favorable in the roadway retaining mining method. The roadway deformation in the advanced abutment pressure area of the working face is small. The mining-induced stress caused by the collapse and compaction of the overlying strata in the goaf is the dominant factor affecting the effect of roadway retaining, especially in the 50-100 m range behind the working face, where the dynamic load causes high bearing capacity of the support elements, large roadway convergence, and roof separation. Temporary support and supplementary reinforcement should be added when necessary. The monitoring system presented in this study is highly comprehensive, simple, reliable, and low in cost, providing a reference for roof cutting roadway retaining projects and roof caving-related studies.

Quasi-zero stiffness vibration isolators with slender Euler beams as positive stiffness elements

Based on the combination of the high bearing capacity of a slender Euler beam before buckling and low stiffness in the postbuckling range near the critical condition after loading, a novel quasi-zero stiffness (NQZS) isolator with enhanced vibration isolation capability is proposed using slender beams as positive stiffness elements. The proposed NQZS isolator can obtain a much large range with ultralow system stiffness maintaining the bearing capacity. Its vibration isolation performance was robust to equilibrium position deviation, which is essential for engineering practice. The correctness of the theoretical analysis was confirmed by the agreement between the experimental and theoretical results.

Laser‐Induced Polymerization of Photosensitive Resin for Silk Fabric Joining

Herein, a new joining method for silk fabrics based on polymerization of polyurethane acrylate (PUA) photosensitive resin induced by a nanosecond 355 nm ultraviolet laser is proposed. After the resin is applied and cured, not only the space between the fiber bundles, but also the gaps within the bundles are filled up with the resin, forming strong interlocking bonds. The infrared spectra of the joint area indicate that there is no textile burning or chemical change on silk fibers. The increase of laser energy density can improve the polymerization degree of the resin and increase the joint strength. However, when the energy density exceeds 1.68 J cm−2, ablation of the photosensitive resin occurs. The amount of filled resin affects the thickness of the joint and its strength. When the resin filling rate is 0.76 mL min−1, the joint has a high filling density and high bearing capacity. The tensile force of the joint reaches 297.10 N, which is higher than the breaking force of the base silk fabric. The tensile force of the joint also increases with the increasing of the joint width. This study provides an alternative process for conventional sawing and stitching in garments fabrication.

Tribomonitoring of the quality of aviation hydraulic oils according to lubricity and rheological indicators

The study proposes a diagnostic control method for assessing the quality of commercial batches of hydraulic oils based on the kinetics of changes in the thickness of lubricating layers, shear stresses of the lubricating material, and effective viscosity in tribotechnical contact. Timely and high-quality tribomonitoring of lubricants provides a perspective on their rational use and reduced wear of equipment parts. The developed methodology simulates the operation of gears in rolling conditions with a slip of 30% using a roller analogy. Samples of AMG-10 oil from two manufacturers were analyzed. For "Bora B" AMG-10 oil (sample 1) with gradients of the sliding speed of the lubricating layer in contact from 5.63·103 to 5.73·105 с-1, the effective viscosity is set at the level of 4249 and 5039 Pa·s at a bulk oil temperature of 20 and 100 oС, respectively, which indicates the resistance of oil components to destruction under conditions of increasing shear rate gradient. For AMG-10 oil (sample 2), the effective contact viscosity decreases by 1.53 times both at an oil temperature of 20 oС and at 100 oС and is 2764 Pa·s (at 20 oС) and 3309 Pa·s (at 100 oС), which indicates the destruction of the components of the lubricant. For "Bora B" AMG-10 oil, effective lubricating properties have been established both during the start-up period and at maximum revolutions in conditions of rolling with slipping. It was shown that at start-up, regardless of the temperature of the lubricant, the mixed lubrication mode dominates. At the maximum revolutions of the tested samples, the hydrodynamic lubrication mode dominates, which indicates the effective lubricating properties of the Bora B AMG-10 oil. According to the kinetics of changes in the rheological parameters of oils, it was established that the resistance of the lubricant's components to mechano-thermal destruction under non-stationary lubrication conditions contributes to the effective formation of a lubricating layer in contact with a high bearing capacity

Field Test Study on the Bearing Capacity of Extra-Long PHC Pipe Piles under Dynamic and Static Loads

Pretensioned prestressed high strength concrete (PHC) pipe piles are widely used in various engineering foundations, which have the advantages of high single pile bearing capacity, strong adaptability to geological conditions and high degree of construction mechanization. In order to study the vertical compressive bearing performance and settlement characteristics of ultra-long PHC pipe piles, high strain dynamic detections and static load tests were carried out on four PHC piles with a diameter of 0.9 m on site. It can be seen from the field test that the bearing capacity of the prefabricated pipe piles was time-dependent. By the end of the dynamic test, the bearing capacity of each test pile increased by 27% to 66%. The static load test also verified the rationality of the value of the restitution coefficient. Therefore, the final bearing capacity of the pile foundation can be predicted by using the high strain initial driving results and the restitution coefficient, which can reduce the repeated driving process, effectively save the cost and improve the engineering efficiency. Under 2.1 times the design load, the change range of the pile concrete modulus is from 37.5 GPa to 52 GPa, the change range of the pile side friction resistance is from 0 kPa to 97 kPa and the change range of the pile end to pile bottom load ratio is from 0% to 7.54%. During the test, the shaft friction and end bearing of the lower part of the piles were not fully mobilized. The shaft friction resistance, the end resistance and the movement behavior of the pile top and the end of the piles can provide parameter references for the subsequent design and construction of the piles.