Increase Of Vertical Load Research Articles

Disintegration behavior and its grading entropy characterization of polyurea modified graded carbonaceous mudstone under loading and drying-wetting cycles

To study the disintegration behavior and characterization indexes of Modified Graded Carbonaceous Mudstone (MGCM), soaking disintegration tests of MGCM under vertical loading and cyclic drying-wetting were carried out with a disintegration test instrument which self-designed by our team. The grain size distribution of MGCM during drying-wetting cycles was analysed. Standard basal entropy, as an important parameter of grading entropy that quantitatively characterizes distribution curves, was introduced to characterize the disintegration behavior of MGCM and correlated with the comprehensive evaluation index, namely, disintegration ratio. The results show that as the number of drying-wetting cycles increases, the Graded Carbonaceous Mudstone (GCM) blocks disintegrate rapidly and the fine-grain content increases. With an increase in vertical load, the particles disintegrate more completely. The contents of each particle group in the GCM test groups stabilize after 9, 7, and 4 drying-wetting cycles under vertical loads of 0, 100, and 200 kPa, respectively. Under the same vertical load of 200 kPa, the contents of each particle group in MGCM test groups with Polyurea (PU) content 0, 5, and 10 wt% stabilize after 4, 6, and 8 drying-wetting cycles, respectively. The inclusion of PU can effectively retard the disintegration of GCM, and the effect is more pronounced with 5 wt% PU content compared to 10 wt%. However, it is also susceptible to the deterioration of PU layer caused by mechanical screen. The grading entropy model of MGCM under loading and cyclic drying-wetting is established. There is a significant positive, linear correlation between the standard basal entropy and the disintegration ratio. A smaller standard basal entropy to a smaller disintegration ratio, indicating a greater degree of particle disintegration and fragmentation. The standard basal entropy can characterize the disintegrated particles of MGCM with different PU content under vertical loading and drying-wetting cycles. The standard basal entropy of GCM decreases rapidly initially and then stabilizes as the number of drying-wetting cycles increases. The standard basal entropy decreases exponentially as the vertical load increases. The results provide a new quantitative index for analyzing the grading characteristics of MGCM following disintegration, which are valuable for engineering construction and disaster prevention in carbonaceous mudstone areas.

Study on seismic performance test and calculation method of recycled steel fiber reinforced concrete shear wall

SummaryRecycled steel wire is taken from used tires, and by procedures like mechanical cutting and friction treatment, it can be converted into industrial recycled steel fiber that meets precise criteria. Such green fiber may effectively limit the growth of fractures in concrete and diffuse the fracture energy of concrete when incorporated into concrete. An investigation of the effects of materials and horizontal reinforcement spacing on the seismic performance of shear wall specimens is presented in this research. The test and numerical simulation findings indicate that the RSFRC (recycled steel fiber reinforced concrete) shear wall's fracture is substantially narrower than that of a conventional shear wall and that the shear carrying capacity and deformation ductility of the shear wall have been greatly enhanced. The energy dissipation capacity of the RSFRC shear wall specimen with varying horizontal reinforcement spacing is significantly enhanced when compared to the conventional shear wall, and the ultimate displacements are reduced. RSFRC shear wall specimen has higher stiffness in the early stage, and the overall stiffness decreases slowly. With the decrease of fiber volume fraction of RSFRC shear wall in a certain range, the shear bearing capacity and stiffness of the model will decrease slightly, but the ductility will increase significantly. Compared with the RSFRC shear wall with fiber aspect ratio of 40 and 25, the bearing capacity and ductility of the two are close, but the RSFRC shear wall with low aspect ratio is slightly insufficient. When the axial compression ratio is in the range of 0.2–0.4, the horizontal shear capacity of RSFRC shear wall increases with the increase of vertical load, but the maximum horizontal displacement becomes smaller, and the model is damaged by compression. Using theoretical calculation, this work also creates the simplified calculation method and restoring force model for the bearing capacity of the diagonal section of RSFRC shear wall. The observed findings correspond well with the test hysteresis curve and may serve as a benchmark for future study. This study provides a new research direction for the seismic performance of RSFRC structures, as well as a solid theoretical foundation and promotion for future research.

Evaluation of Agriculture Tires Deformation Using Innovative 3D Scanning Method

This study presents the results of research related to agriculture tire deformation under variable vertical load and inflation pressure. The research objects were two tires of the same size and different internal structures. Three levels of inflation pressure and five levels of vertical load were used. The loaded tire with each inflation pressure was scanned using the 3D scanner—the effect of this operation was a three-dimensional image of a tire part (near the place of contact with the surface). The next step was the creation of vertical and horizontal cross-sections of the tire profile, which allowed the analysis of tested parameters: profile height, location of the point of maximum tire deflection, the width of the tire profile, and the area of horizontal cross-sections. Finally, the mathematical model was formulated, describing contact areas of horizontal cross-sections as a function of the factors. Based on the conducted research, it was stated that an increase in vertical load caused reductions in both types of heights. Moreover, the width of tire profiles and the area of horizontal cross-sections increased due to the increase in vertical load (for bias-ply, increases were smaller than for radial tires). Similar changes were observed after the reduction of inflation pressure.

Microstructure and tribological properties of Al 7075-TiO2@CNTs composites under T6 treatment

The TiO2 nanoparticles-coated CNTs (TiO2@CNTs) were used as reinforcement to fabricate the 7075-TiO2@CNTs composites via ultrasonic-assisted casting, then the composites were adopted T6 treatment. The microstructures and wear performance were investigated in detail. The TiO2@CNTs could promote the refinement of α-Al grains, reducing the average size by 60.7%. With the addition of 1.0 wt% TiO2@CNTs and introduced T6 treatment, the wear rates have maximally decreased by 48.2% and 69.2%, respectively. The self-lubrication and refinement strengthening effect of CNTs improved the wear resistance, and the strong interfacial bonding between nanoscale MgZn2 precipitates and α-Al further enhanced the tribological properties. The effects of vertical load and sliding velocity on tribological morphology of T6 treatment composites were investigated, demonstrating that with the increase of vertical load, the wear rate and micro-crack tendency increased. Meantime, with the increase of sliding velocity, both the wear rate and the surface roughness showed a decreasing and then increasing trend. The main wear regime was abrasive wear combined with slight oxidation at lower velocities, while delamination wear combined with severe oxidation at higher velocities.

Effect of drying–wetting cycles on the hydromechanical behaviour of compacted coal gangue

Compacted coal gangue is often used as subgrade soils in South Central China. To understand further the effects of drying–wetting (D-W) cycles on the hydromechanical behaviour of compacted coal gangue subgrade, this paper presents a series of laboratory test results on reconstituted coal gangue subjected to multiple D-W cycles. The effects of vertical load and compaction parameters on the soil deformation behaviours during hydraulic loading are fully discussed. Based on the laboratory investigations, the shrinkage strain was found to decrease with the increase in the initial dry density; however, it increased with the increase in vertical load. Experimental results also revealed that the variation in soil water content was more pronounced in the first D-W cycle. The characteristics of the void ratio and water content change during D-W cycles were investigated, and the shrinkage behaviour (e–w) was obtained. Significant hysteresis was detected during the D-W cycles, and the size of the hysteresis loop was found to decrease with the increase in D-W cycles, while it increased with the increase in vertical load. Besides, the D-W cycles were found to influence the pore volume at the microscopic scale, where both the volumes of inter-aggregate pores and intra-aggregate pores were found to decrease as the hydraulic loading increased.

Study on Compressibility and Settlement of a Landfill with Aged Municipal Solid Waste: A Case Study in Taizhou

Capacity expansion of existing landfills is one of the most economical methods of relieving the stress caused by the disposal of local municipal solid waste (MSW) in developing countries. In this paper, the compression characteristics and settlement of the aged MSW in Xiawan landfill were studied. The physical composition, moisture content, volumetric weight, and modified primary compression index of the aged MSW at different depths were tested, and then the settlement of the MSW in the area to be filled with fly ash was calculated. The test results showed that the main components of the aged MSW were muck and textile, indicating that kitchen waste was degraded. The moisture content of the MSW generally increased with depth, and the average moisture content within 5 m of the shallow part of the landfill was 97%. The void ratio of the aged MSW decreased from 4.0 to 2.2 with an increase in vertical load from 1 kPa to 400 kPa. The modified primary compression index of the aged MSW ranged from 0.22 to 0.27, and generally decreased with depth. Under the load generated by the subsequent filling of fly ash, the final strains of the aged MSW was approximately 15% to 20%. The physical composition and compression characteristics of the aged MSW measured in this paper were compared with those reported in previous studies to provide reference for the settlement analysis of landfills with aged MSW.

Study on Seismic Performance of C105 Prestressed High Strength Concrete Hollow Pipe Pile

Prestressed concrete pipe pile with high bearing capacity, the advantages of convenient construction, low cost and widely used in practical engineering, because of the prestressed high strength concrete in use process is in complex stress state, both are under a lot of vertical load, and horizontal seismic action needs to be considered at the same time, it is necessary under the condition of considering the vertical load bearing capacity of prestressed high strength concrete level and considering the loading level, the horizontal bearing capacity. Scholars at home and abroad based on the simple hypothesis, puts forward the calculation method of a lot of interaction with soil, in the future will be adopted in calculation, using ABAQUS finite element analysis, this paper established the three-dimensional finite element model of prestressed concrete pipe pile, respectively under different vertical pressure (P = 4000 kn, P = 4800 kn, P = 6000 kn) one-way load and calculated the horizontal bearing capacity, and under repeated load, respectively to study the size of the different vertical pressure and different reinforcement stirrup ratio on its bearing capacity and seismic performance. The results show that the stiffness of pipe pile decreases significantly with the increase of vertical pressure under different vertical loads. With the increase of vertical load, the ductility and energy dissipation capacity of the components decrease gradually. The horizontal bearing capacity of prestressed high strength concrete pipe decreases with the increase of vertical pressure. However, its amplitude decreases with the increase of vertical pressure value.

Large‐Scale Direct Shear Test on Tire Slice Reinforced Crushed Concrete Particles

In order to study the mechanical properties of tire slices reinforced crushed concrete particles, a series of shear tests were carried out under the conditions of different vertical loads, different tire volume contents, and different shear rates. The test results show that the addition of tire slices can increase the internal friction angle and cohesion of concrete particles, therefore increase the shear strength of crushed concrete particles. The peak shear stress increases with the increase of vertical load. However, with the increase of the tire volume content, the reinforcement effect of the tire slices first increases and then decreases, and the effect is best when the tire volume content is 4%. Under the vertical load of 60 kPa, the reinforcement effect of 4% tire volume content is the best, and the peak shear stress increases by 46.53%. Additionally, the shear rate has a little effect on the peak shear stress. The larger the shear rate is, the smaller the shear displacement is and the faster the shear strength decreases. The smaller the shear rate is, the more gently the shear strength decreases.

Test research on the adhesive and tractive performance of a wheeled tractor

In order to improve the adhesive and tractive performance of a wheeled tractor, the test schemes for the research on the influencing factors of adhesive and tractive performance are designed.The maximum tyre driving force has a linear relation with the vertical load on wheel axis, the tyre deformation displacement increases with increasing tyre driving force. The tyre adhesive performance can be improved with the increase of vertical load and the decrease of tyre pressure, the adhesive and tractive performance on the asphalt road is superior to that on the soil road. Plough resistance, resistance torque and slip coefficient increase with plough depth. When plough depth increases, vibration amplitude decreases, and vibration frequency basically remains unchanged. When slip coefficient is less than 0.05, the drawbar pull is proportional to slip coefficient; when slip coefficient is greater than 0.05, the drawbar pull remains nearly constant.

Test research on the adhesive and tractive performance of a wheeled tractor

In order to improve the adhesive and tractive performance of a wheeled tractor, the test schemes for the research on the influencing factors of adhesive and tractive performance are designed.The maximum tyre driving force has a linear relation with the vertical load on wheel axis, the tyre deformation displacement increases with increasing tyre driving force. The tyre adhesive performance can be improved with the increase of vertical load and the decrease of tyre pressure, the adhesive and tractive performance on the asphalt road is superior to that on the soil road. Plough resistance, resistance torque and slip coefficient increase with plough depth. When plough depth increases, vibration amplitude decreases, and vibration frequency basically remains unchanged. When slip coefficient is less than 0.05, the drawbar pull is proportional to slip coefficient; when slip coefficient is greater than 0.05, the drawbar pull remains nearly constant.

Copper canister shearing in spent nuclear fuel repository using Bodner–Partom model

This paper describes the implementation of the Bodner–Partom model for the analysis of copper corrosion barrier in canisters containing spent nuclear fuel. The Bonder–Partom constitutive model implemented in CODE_BRIGHT finite element code is compared with experimental results for validation and with the Stealth finite difference code for verification. Deep geological disposal is the most reliable alternative for the spent nuclear fuel storage. This disposal is based on the multiple barriers principle. Different barriers will prevent the release of the radionuclides and one of the barriers is the canister that will contain the spent fuel. The canister will be constructed mainly in cast iron for giving mechanical protection to the spent fuel with a copper shell for protecting the cast iron against corrosion. Due to the high strength of metals, the canister components will keep it inside the elastic region during the hydration of the buffer, so it has not been necessary to implement more accurate constitutive models for the simulation. The canister is considered more as a boundary condition rather than a component to be analysed when the hydration and swelling processes are assessed but in case of relative displacements between the lips of joints intersecting a deposition hole because of an earthquake induced by the increase of vertical load due to the accumulation of ice during a glaciation or any other tectonic effect, not likely in Baltic shield, the stresses in canister could be high enough for reaching plastic conditions and in this case, it is considered necessary to use more accurate constitutive models for the simulation of the canister–buffer system.

Experimental study on shear characteristics of reef coral sand

Coral sand is an important raw material for the construction of ocean infrastructure. Due to its special chemical composition, loose granular structure and great difference in physical and mechanical properties between coral sand and land-based silica sand, it is of great significance to conduct in-depth research on it. The shear characteristics of coral sand from the south China sea were studied by setting different relative compactness and vertical loads. The results show that both the relative compactness and the vertical load affect the shear stress-shear displacement curve of coral sand. With the increase of vertical load, the curve gradually changes from strain hardening to strain softening. With the increase of relative compactness, coral sand showed strain softening characteristics gradually. The increase of relative compactness can enhance the shear strength of coral sand, and the internal friction angle and cohesion increase linearly with the increase of relative compactness level. Therefore, the bearing capacity of coral sand foundation can be effectively enhanced by continuously increasing the relative compactness of soil in engineering.

Experiment of the Swell-shrink Characteristic of the Improved Red Clay under the Dry and Wet Circulation

After a preliminary study on the swell-shrink characteristic of the red clay of somewhere in Chongqing under the effect of dry and wet circulation through the laboratory geotechnical experiment, in order to study the swell-shrink characteristic of the improved soil under the function of dry-wet circulation, two admixtures of lime and cement were added to the red clay. The results show that: Under the same load condition, the swell-shrink deformation of the modified red clay decreases gradually with the increase of the number of dry and wet circulation, and finally reach to a stable. Under the effect of the same dry and wet circulation, the swell-shrink deformation of the improved red clay decreases with the increase of vertical load. The conclusions have some reference value for the engineering construction of similar ground soil.

Seismic behaviour of ashlar stone masonry walls with enhanced mortar joints

Stone masonry walls may be constructed using different types of stonework. This paper investigates the effectiveness of a technique that strengthens traditional ashlar stone masonry by embedding polymer mortar and steel bars in bed joints. The seismic behaviour of stone masonry walls with enhanced mortar joints is experimentally evaluated. Seven single-bay, single-storey wall specimens were fabricated and tested under different combinations of constant vertical loads and reversed cyclic lateral loads. One specimen was constructed using a traditional construction method; the other six specimens were constructed similarly, but their joints were strengthened with a combination of embedded polymer-based mortar and steel reinforcing bars. The influence of applied normal stress and strengthening method on the failure mode, lateral resistance, strength degradation, stiffness degradation, energy dissipation and ductility was investigated. The experimental results show that strengthening the joints effectively enhances the lateral load-carrying capacity and integrity of stone masonry walls. As expected, an increase in vertical load increased both the lateral strength and pre-peak stiffness of the tested specimens, but decreased the ductility. Within the limitation of the present tests, the failure mechanisms of the stone masonry walls were dominated by either diagonal stepped cracks or slip-shear cracks, depending on the specific strengthening method.

Finite element modeling of the interaction of a treaded tire with clay-loam soil

In the present study, a treaded tire-soil interaction model was developed and its results were validated with laboratory data. In the laboratory test plaster molding was used to obtain contact area and contact volume. Experimental and FEM modeling results for output parameters such as the contact area, contact volume, and rolling resistance showed close agreement. Increasing soil moisture significantly decreased the maximum contact pressure transmitted to soil due to an increase in tire-soil contact area. Also, increasing soil moisture, increased the effect of stress on the soil, which, in turn, increased soil deformation in each layer and consequently the total soil sinkage. In all three levels of moisture tested in this study, an increase in vertical load and tire inflation pressure increased the tire-soil contact volume. At a constant soil moisture level, tire inflation pressure variations affected compaction at the top-soil layers and did not affect compaction changes in the sub-layers. Moreover, variations of the vertical load on the tire changed compaction at the top and sub-soil layers significantly.

Development of a Single Wheel Test Rig for Measuring Motion Resistance

Research on soil-wheel interaction is essential in studies of motion resistance of narrow wheels of agricultural machines. The aim of this research was to study the effects of soil moisture content and tyre inflation pressure on motion resistance of narrow wheels using a locally developed single wheel test rig. A single wheel Test Rig facility was developed at Federal University of Technology, Akure. It consists of a soil bin, carriage, single narrow wheel tester, trolley and drive system. An existing indoor soil bin facility was equipped with a soil bin which dimension was 9.76 m length x 1.98 m width x 0.92 m high. The single-wheel test facility was utilized to investigate the effect of tyre inflation pressure and vertical load on motion resistance of wheel. Two narrow wheels of 90/10-10 in width, IRC MB90 tyre were used as the test wheels on clay soil and were separately installed on a carriage that traversed the length of soil bin. Two inflation pressures of 274 kPa and 380 kPa and four levels of vertical load applied on wheel (i.e. 15, 20, 30, and 40 kg) were examined at two different soil moisture conditions (bulk density of 1.58 g/cm3 and 1.55 g/cm3, soil moisture content of 8% and 10% dry basis and soil penetration resistance of 1.02 MPa and 1.5 MPa). Exponential regression was obtained for the two wheels to check for linearity at different moisture content, R2 value for test wheel 1 with inflation pressure of 270 kPa at 8% moisture content was 0.9974 while that of inflation pressure of 380 kPa at 10% moisture content was 0.9952; also for test wheel two (2) R2 value was 0.9977 and 0.9914 at moisture content of 8% and 10% respectively, this shows for test wheel 1 with inflation pressure of 270 kPa at 8% moisture content showed more motion resistance compared to motion resistance of test wheel 1 at inflation pressure of 380 kPa and 10% moisture content, while for test wheel 2 with inflation pressure of 270 kPa showed low motion resistance at 8% motion content. The effect of different inflation pressures and vertical loads on the motion resistance of the narrow wheels has been investigated under different moisture content (8% and 10%). The contact area for all tests was in the range of 309-330 cm2, average contact pressure increased nearly linearly with increase in vertical load and increase in inflation pressure The research provides data that are relevant in the study of soil-wheel interaction.

Evaluation of Undrained Bearing Capacities of Wide‐Shallow Bucket Foundation with Honeycomb Bulkheads in Clay

As a new type of offshore wind foundation, the wide‐shallow bucket foundation with honeycomb bulkheads mainly bears vertical, horizontal, and moment loads. As yet, no systematic study has been conducted regarding the effects of honeycomb bulkheads on the undrained bearing capacities of the wide‐shallow bucket foundation. In this study, a large number of three‐dimensional (3D) finite element (FE) analyses were performed to investigate the undrained bearing capacities of the wide‐shallow bucket foundations with and without honeycomb bulkheads, thereby evaluating the influence of honeycomb bulkheads on the bearing capacities under different conditions. The results show that under uniaxial loading, the uniaxial bearing capacities of the wide‐shallow bucket foundation are basically unaffected by the honeycomb bulkheads in homogeneous clay. For nonhomogeneous clay, the moment bearing capacity will be considerably enhanced with the increase in soil shear strength heterogeneity. Under combined loading, the honeycomb bulkheads will enhance the combined bearing capacities only in nonhomogeneous clay. The enhancement effects will increase with the increase in soil shear strength heterogeneity but decrease with the increase in vertical load. Besides, the simplified equations for calculating the uniaxial bearing capacities of the wide‐shallow bucket foundation with honeycomb bulkheads are also proposed considering the influence of embedment ratio and soil shear strength heterogeneity. At last, the parameters of an approximating expression are fitted to predict the failure envelopes of this foundation under combined loading.

Analysis of escalator tunnels deformations, when exposed to soils freezing

The presented work studies deformation processes of escalator tunnels support lining constructed by means of soils freezing in difficult engineering and geological conditions. The features of construction technology are considered. The features of the freezing effects during the active, passive stage of freezing and during the natural thawing of soils are considered. The data of the long-term arch support monitoring, as well as the earth’s surface is presented. The non-standard nature of geomechanical processes, in particular the support lifting during the construction of the escalator tunnel is revealed. Methods of mathematical statistics and error theory were used to process and analyze data of field observations at surface and array displacements and deformations. According to survey observations on a few escalator tunnels in Saint-Petersburg underground the correlation form shown is increased in horizontal diameter of the rings and reduce the vertical dependence of the sedimentation casing from subsidence of the earth’s surface. The data also reveals that with increasing development depth, despite the increase in vertical load, the deformation of the lining is reduced, which is associated with physical and mechanical properties of the array.

Flat slab strengthening techniques against punching-shear

Over the years, the flat slab system has become a popular form of construction in many countries, particularly for multi-storey buildings such as offices or carparks. Nowadays, a considerable number of flat slab buildings requires strengthening against punching. Reasons are several, like design or construction errors, poor quality materials, not complying with new codes provisions, or increase of vertical load. This paper discusses different techniques for strengthening of R/C slabs against punching: insertion of post-installed shear reinforcement, application of external fibre reinforced polymers or a bonded reinforced concrete overlay (BRCO) on the slab top surface, enlargement of the support, application of a post-tensioning system. The authors propose a unified approach, based on the Critical Shear Crack Theory (CSCT), to evaluate the effectiveness of each strengthening technique. The attempt is to give a reading key capable of adapting to different strengthening techniques and providing a comprehensive view of the problem. The study shows that the CSCT could be easily adapted to all strengthening techniques and punching strength predictions are in good agreement with literature experimental results. This work also proposes to give designers the tool to choose which strengthening technique suits better to the specific case.

Lateral Response of a Single Pile under Combined Axial and Lateral Cyclic Loading in Sandy Soil

According to practical situation, there have been limited investigations on the response of piles subjected to combined loadings especially when subjected to cyclic lateral loads. Those few studies led to contradictory results with regard to the effects of vertical loads on the lateral response of piles. Therefore, a series of experimental investigation into piles in dense sand subjected to combination of static vertical and cyclic lateral loading were conducted with instrumented model piles. The effect of the slenderness ratio (L/D) was also considered in this study (i.e. L/D= 25 and 40). In addition, a variety of two-way cyclic lateral loading conditions were applied to model piles using a mechanical loading system. One hundred cycles were used in each test to represent environmental loading such as offshore structures. It was found that under combined vertical and cyclic lateral loads the lateral displacement of piles decreased with an increase in vertical load whereas it causes large vertical displacements at all slenderness ratios. In addition, for all loading conditions the lateral, vertical (settlement and upward) displacements and bending moments increased as either the magnitude of cyclic load or the number of cycles increases.