Static Pressure Method Research Articles

Experimental study on penetration characteristics of an open-ended pile under static and dynamic driving methods

Open-ended piles have been widely adopted in both offshore and onshore geotechnical engineering projects. However, the influence mechanism of pile driving methods on the penetration characteristics of the open-ended piles is not clear. Therefore, this paper presents simulations of an open-ended pile penetrating through a silt layer to a fine sand bearing stratum using static and dynamic driving methods respectively in a series of indoor model tests. Properties including pile sinking resistance, pile end resistance, pile side friction resistance, pile load transfer law and soil plug formation during penetration are analyzed. The results show that the PLR value of the hammered pile is always greater than that of the static pressure pile in the stable sinking stage, while the IFR value of the latter in the sand layer is significantly higher than that of the former. The resistance of the hammered pile under the same penetration depth is less than that of the static pressure pile and increases sharply when entering the holding layer. In addition, the final pile driving resistance of the hammering method is 66.68% of the static pressure pile driving resistance, and the pile end resistance from the static pressure method and hammering method account for 75.4% and 77.6% of the total resistance respectively In the choice of construction method, the static pressure method is more suitable for silty soil, and the hammering method can show its advantages in fine sand formation.

Mechanical-strength-growth law and predictive model for ultra-large size cement-stabilized macadam based on the vertical vibration compaction method

The mechanical properties of ultra-large particle size cement-stabilized macadam (CTB-50) and traditional cement stabilized macadam (CTB-30) have been tested, and the correlation between the vertical vibration compaction method (VVCM), the static pressure method (PCT), and mechanical strength of field core samples has been confirmed. The mechanical strength growth equation and mechanical strength growth model of cement-stabilized macadam are proposed and tested for dependability. Correlation between the VVCM sample and field core sample is higher, reaching up to 90%, and the gradation change after compaction is less. In addition, the correlation coefficients of the mechanical strength growth equation and mechanical strength growth model of cement stabilized macadam with the indoor test results were 97% and 92%, respectively. And the error between the simulated and test values is <14%. CTB-50 has greater mechanical strength and requires less cement content, which can reduce cement cost, reduce base cracking problems, and extend pavement service life.

Deterioration characteristics of cement-improved loess under dry-wet and freeze-thaw cycles.

The effects of cement dosage, compaction coefficient, molding method (vertical vibration method and static pressure method), and dry-wet and freeze-thaw cycles on the mechanical strength of cement-improved loess (CIL) were studied to reveal its strength degradation law under dry-wet and freeze-thaw cycles. Results show that when using the vertical vibration molding method, the strength degradation effect of CIL can be improved by increasing the cement dosage and compaction coefficient; however, it is not obvious. Under the action of dry-wet cycle, damages, such as voids and cracks of CIL, develop continuously. Further, the strength deteriorates continuously and does not decrease after more than 15 dry-wet cycles. Therefore, the dry-wet cycle degradation system is selected by considering the most unfavorable conditions. In the process of freeze-thaw alternation, the pores and fissures of CIL develop and evolve continuously and the strength deteriorates continuously under the joint influence of water and low temperature. The strength tends to become stable after more than 12 freeze-thaw cycles. According to the safety principle, the deterioration coefficient of the freeze-thaw cycles is 0.3.

Optimal Dynamic Duct Static Pressure Method in a Multi-Zone Variable Air Volume System

Reducing the energy consumption of a variable air volume (VAV) system in heating, ventilation, and air-conditioning (HVAC) systems attracts many attentions. In this letter, a novel method, namely, optimal dynamic duct static pressure (ODSP) method is proposed to find the globally optimal solutions of the original non-convex multi-zone VAV system energy optimization problem. Our method is based on the primal dual interior point method to solve an equivalent convex optimization problem of the multi-zone VAV system energy optimization problem. Different from existing methods, our method is a real-time optimization method and explicitly considers the duct network model to find the energy saving strategy. Numerical simulations illustrate the effectiveness of our method compared with current methods, which show that our method provides better energy efficiency and nearly 20% energy is saved. Our method also has the guarantee to find the optimal solutions.

Optimized Design of Aluminium Bumper by Impact Test and Computer Simulation Analysis

Aiming at target steel car bumper new lightweight design, with a target vehicle steel bumper static crushing, three static pressure and impact test and simulation analysis based on the performance parameters, design targets bumper car aluminum alloy box, the section size of anticollision beam and the energy absorption and the materials they need to determine the aluminum bumper performance. The three-point static pressure method is used to optimize the design of the anti-collision beam. Because the loading condition is relatively simple, the optimization function of optistruct is used to optimize it to determine the cross-section shape and size of the anti-collision beam.

Investigation on cement-improved phyllite based on the vertical vibration compaction method.

The vertical vibration compaction method (VVCM), heavy compaction method and static pressure method were used to form phyllite specimens with different degrees of weathering. The influence of cement content, compactness, and compaction method on the mechanical properties of phyllite was studied. The mechanical properties of phyllite was evaluated in terms of unconfined compressive strength (Rc) and modulus of resilience (Ec). Further, test roads were paved along an expressway in China to demonstrate the feasibility of the highly weathered phyllite improvement technology. Results show that unweathered phyllite can be used as subgrade filler. In spite of increasing compactness, phyllite with a higher degree of weathering cannot meet the requirements for subgrade filler. With increasing cement content, Rc and Ec of the improved phyllite increases linearly. Rc and Ec increase by at least 15% and 17%, respectively, for every 1% increase in cement content and by at least 10% and 6%, respectively, for every 1% increase in compactness. The higher the degree of weathering of phyllite, the greater the degree of improvement of its mechanical properties.

Study on influencing factors of unconfined penetration test based on orthogonal design

Tensile strength is one of the most important mechanical parameters controlling the development of cracks in loess plateau. The unconfined penetration test (UPT) is often used as an index for prediction of soil tensile strength properties. However, suffering the influence of the experiment condition, its uncertainty and sensitivity analysis to various experiment parameters was still unknown. Therefore, this study designed orthogonal tests and conducted the sensitivity analysis of influence factors (water content, dry density, steel disk (punch) diameter, height-diameter ratio, specimen preparation method, and loading rate) on the tensile strength of loess by using UPT. The statistical analysis of the test results indicated the order that affects tensile strength of the loess was water content, disk diameter, dry density, sample preparation method, height to diameter ratio, and loading rate respectively. The tensile strength of loess presented a tendency to increase at first and afterward to decrease as the increase of the punches diameter in UPT. The tensile strength reached a maximum value for a 24.72-mm disk diameter. According to the failure mode of the specimen, 12.3 to 20.5 times height-diameter ratio punches diameter range was considered appropriate. Furthermore, in the reconstituting specimen preparation method of disturbed loess, positive and reverse static pressure method was beneficial to the gain on the tensile strength. Maintaining a 1-mm/min loading rate, the variance of tensile strength was optimal. Moreover, the interactions of factors had significant effects on the tensile strength in UPT. The achieved results can provide the references and analytical analysis for standardizing UPT to measure the loess tensile strength.

Effect of superabsorbent polymer on mechanical properties of cement stabilized base and its mechanism

Abstract Superabsorbent polymers (SAPs) are cross-linked polymers that can absorb and retain large amounts of water. In recent years, a growing interest was seen in applying SAPs in concrete to improve its performance due to its efficiency in mitigating shrinkage. This paper presents findings in a study on effect of SAPs on performance of cement-treated base (CTB), using the experience of internal curing of concrete. CTB specimens with and without SAPs were prepared and tested in the laboratory. Tests conducted include mechanical property testing, dry shrinkage testing, differential thermal analysis, mercury intrusion porosimetry and scanning electron microscope testing. It was found that 7-day and 28-day unconfined compressive strength of CTB specimens with SAPs was higher than regular CTB specimens. 28d compressive strength of CTB specimens with SAPs made by Static pressure method was 5.87 MPa, which is 27% higher than that of regular CTB specimens. Drying shrinkage of CTB specimens with SAPs was decreased by 52.5% comparing with regular CTB specimens. Through the microstructure analysis it was found that CTB specimens with SAPs could produce more hydration products, which is also the reason for the strength improvement.

Effects of Cement Content, Curing Period, Gradation, and Compaction Degree on Mechanical Behavior of Cement‐Stabilized Crushed Gravel Produced via Vertical Vibration Test Method

In this paper, the reliability of vertical vibration test method (VVTM) was evaluated by comparing the changes in moisture content and gradation before and after forming the test piece by VVTM and static pressure method and the mechanical strength correlation between the laboratory compaction sample and the core sample in the field. The effects of cement content, curing period, gradation, and compaction degree on the unconfined compressive strength, splitting strength, and compressive rebound modulus of VVTM‐compacted cement‐stabilized crushed gravel (CSCG) were studied, and a mechanical strength prediction equation for VVTM‐compacted CSCG was formulated. The results show that the correlation between the strength of the VVTM specimen and the field core sample can reach 92%; the mechanical strength of CSCG will increase with increase in the cement content, and when the cement content reaches approximately 4%, the increase in its mechanical strength will slow down; the mechanical strength of VVTM‐compacted CSCG with different cement dosages and gradation types increased fast at 14 days of curing period and began to level off after 90 days. Compared with XM gradation, using GM gradation can improve the mechanical strength. Under different gradations and curing periods, the mechanical strength linearly increases with increase in the degree of compaction. The mechanical strength prediction equation has a high reliability; therefore, it can accurately predict the strength growth rules. Moreover, the degree of compaction increases by 1%, and the mechanical strength increases by approximately 10%.

Development and Characterization of Non-Evaporable Getter Thin Films with Ru Seeding Layer for MEMS Applications.

Mastering non-evaporable getter (NEG) thin films by elucidating their activation mechanisms and predicting their sorption performances will contribute to facilitating their integration into micro-electro-mechanical systems (MEMS). For this aim, thin film based getters structured in single and multi-metallic layered configurations deposited on silicon substrates such as Ti/Si, Ti/Ru/Si, and Zr/Ti/Ru/Si were investigated. Multilayered NEGs with an inserted Ru seed sub-layer exhibited a lower temperature in priming the activation process and a higher sorption performance compared to the unseeded single Ti/Si NEG. To reveal the gettering processes and mechanisms in the investigated getter structures, thermal activation effect on the getter surface chemical state change was analyzed with in-situ temperature XPS measurements, getter sorption behavior was measured by static pressure method, and getter dynamic sorption performance characteristics was measured by standard conductance (ASTM F798–97) method. The correlation between these measurements allowed elucidating residual gas trapping mechanism and prediction of sorption efficiency based on the getter surface poisoning. The gettering properties were found to be directly dependent on the different changes of the getter surface chemical state generated by the activation process. Thus, it was demonstrated that the improved sorption properties, obtained with Ru sub-layer based multi-layered NEGs, were related to a gettering process mechanism controlled simultaneously by gas adsorption and diffusion effects, contrarily to the single layer Ti/Si NEG structure in which the gettering behavior was controlled sequentially by surface gas adsorption until reaching saturation followed then by bulk diffusion controlled gas sorption process.

Measurement and Analysis of Performance of 2# Main Ventilator of East Two Shaft in Yaoqiao Coal Mine

According to the existing conditions of the fan installation, we used precision barometer equipment and static pressure method to make a performance test about anti-explosion extraction axial fan in East Two Shaft under the condition of no shut down. According to the parameters of the test, we drew the performance curve of output power, wind pressure, efficiency and air volume about main fans of East Two Shaft in Yaoqiao Coal Mine. By measuring the results and analyzing data, it indicates that the main ventilator is in a good performance to meet the needs of air volume of East Two Shaft. To ensure the safe and economic operation of the main fan, the corresponding improvement measures aiming at the existing shortcomings of the ventilation system of East Two Shaft are put forward. The test method and results of the ANN-2500/1250 fan performance test have certain reference significance for the test of the similar axial fan.

Life Prediction on a T700 Carbon Fiber Reinforced Cylinder with Limited Accelerated Life Testing Data

An accelerated life testing investigation was conducted on a composite cylinder that consists of aluminum alloy and T700 carbon fiber. The ultimate failure stress predictions of cylinders were obtained by the mixing rule and verified by the blasting static pressure method. Based on the stress prediction of cylinder under working conditions, the constant stress accelerated life test of the cylinder was designed. However, the failure data cannot be sufficiently obtained by the accelerated life test due to the time limitation. Therefore, most of the data presented to be high censored in high stress level and zero-failure data in low stress level. When using the traditional method for rupture life prediction, the results showed to be of lower confidence. In this study, the consistency of failure mechanism for carbon fiber and cylinder was analyzed firstly. According to the analysis result, the statistical test information of carbon fiber could be utilized for the accelerated model constitution. Then, rupture life prediction method for cylinder was proposed based on the accelerated life test data and carbon fiber test data. In this way, the life prediction accuracy of cylinder could be improved obviously, and the results showed that the accuracy of this method increased by 35%.

Multi-parameter integrated experimental analysis of wall compaction effect on Semi-automatic plastering machine

Semi-automatic wall plastering machine can effectively reduce the labor intensity of workers, increase operational efficiency in the construction process. A problem is solved how to select its work parameters. In order to obtain the best working conditions of a certain wall plastering machine, this paper has studied hydrostatic compaction process of the wall plastering machine. According to “Standard of the Architectural Decoration Project Quality Approval” in China, mortar compaction effects in cases of different plastering speed, rotation speed of the screw auger, and mortar consistency have been obtained by experiments. Using static-pressure method for wall plastering, experimental results showed that the best plastering speed, screw auger rotation speed and mortar consistency is in the range of 17~18.2cm/s, 55~65r/min and 78~86mm.

Research on the Mechanical Properties and Micro-Morphology of the Cement Stabilized Gravel with Rubber Particles

The primary objective of this paper was to study the mechanical properties of the cement stabilized gravel by different compact method which added rubber particles by using macroscopic and microscopic test. Through test of compression, relationships of mechanical properties of samples were studied. Pore structure and fractal characteristic of mixture was analyzed quantitatively using mercury intrusion porosimetry (MIP), scanning electron microscope (SEM) was applied to analyze the micro-morphology of samples. The tests results showed that the compressive strength of samples which prepared by using vibrating method was greater than that by static pressure method. Compressive strength of samples from vibrating method or static pressure method decreased with the rubber particles volume fraction increase. MIP tests showed that the mean pore diameter and porosity of mixture increased from about 70nm to 250nm and 9% to 24% with the rubber particles content increasing, respectively. SEM tests showed that the interface bonding between sand and hardened cement paste was better than that of between rubber particles and hardened cement paste.

Research on Flow Characteristics of Ultra-high Pressure Impinging Stream Micro-generator

Design a new dynamic ultrahigh pressure structure in this article, This structure include three main zones. Simulate and analyze flow characteristics of three zones in details, providing the basis for the design of micro-size structure with ultra-high pressure. Liquid has gone through three broken and decentralized processes in micro-channels zone、impacting wall zone and flow impinging each other zone, find rule of mirror distribution in impinging zone. According to which, obtain the structure is reasonable. The fresh red wine is experimented, verifying that to obtain the same effect, dynamic ultrahigh pressure method greatly reduce energy consumption than ultra-static pressure. Further put forward and verifying a new method that is combining static and dynamic ultrahigh pressure method, can use a relatively lower pressure to get higher pressure treatment effect. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2390

Experimental Research the Pavement Performance on Chloride-Based Weak Saline Soil

The pavement performance (CBR and modulus of resilient) of the weak chloride-based saline soil was studied by experiment. Samples were made through the static pressure method and vibration method. The test results for the samples under the conditions of non-soaking and soaking made a comparative study. The weak saline soil was analyzed as embankment feasibility. The results showed that: the pavement performance of samples made by vibration method was superior to that of static pressure method; the CBR value and modulus of resilient of samples could meet standard requirements when degree of compaction met the standard requirements. Weak chloride-based saline soil proved to be the road embankment fillers.

Hood Entry Coefficients of Compound Exhaust Hoods

A traditional method for assessing the flow rate in ventilation systems is based on multiple readings of velocity or velocity pressure (VP) (usually 10 or 20 points) taken in ductwork sections located away from fittings (> seven × diameters of straight duct). This study seeks to eliminate the need for a multiple-point evaluation and replace it with a simplified method that requires only a single measurement of hood static pressure (SPh) taken at a more accessible location (< three × diameters of straight duct from the hood entry). The SPh method is widely used for the assessment of flow rate in simple hoods. However, industrial applications quite often use compound hoods that are regularly of the slot/plenum type. For these hoods, a “compound coefficient of entry” has not been published, which makes the use of the hood static pressure method unfeasible. This study proposes a model for the computation of a “compound coefficient of entry” and validates the use of this model to assess flow rate in two systems of well-defined geometry (multi-slotted/plenum and single-slotted/tapered or “fish-tail” types). When using a conservative value of the slot loss factor (1.78), the proposed model yielded an estimate of the volumetric flow rate within 10% of that provided by a more comprehensive method of assessment. The simplicity of the hood static pressure method makes it very desirable, even in the upper range of experimental error found in this study.

Research about Different Molding Methods’ Effect on the Resistance against Frost and Shrinkage of Cement Stabilized Gravel

Through the test research of the two different molding methods of vibration and static pressure, including the analysis of traditional heavy compaction and the new vibration compaction, we could see that the result of the vibration could satisfied the field construction. Analysis of mechanical property was 7d unconfined compressive strength, at the same dose of cement, the strength of vibration was higher than the static pressure method’s and it was more rational and effective for the field control of the construction. Evaluation of water stability was up to the 28d and 5 times freezing-thawing tests, and the resistance ability against frost of vibration was better than the static pressure method. So adopting the vibration method could improve the resistance performance against frost of the road in northeast region of freezing-thawing in spring. From the 7d dry shrinkage test we got that the adopting the vibration method the resistance performance of dry shrinkage was much better and could improve the resistance against shrinkage of the road.

Crystal Structure and Resistance-Temperature Characteristic of the Boron-Doped Diamonds Synthesized from Fe-Ni-C-B System

In the present paper, boron-doped diamond was synthesized by static pressure method using Fe-Ni-C-B system catalyst, whose resistance-temperature characteristic curve was studied. Experiments results proved that the boron-doped diamond has different ionization energy in different temperature interval and the reasons were analyzed. The maximum operating temperature is about 773K for such boron-doped diamond. The research provides experimental basis for high-temperature semiconductor diamond.

An evaluation of industrial ventilation troubleshooting methods in experimental systems.

This study determined the efficacy of specific methods of identifying and locating obstructions and alterations to industrial exhaust ventilation systems under challenging conditions when measurement errors were minimized. Two traditional screening methods were evaluated: (1) two variations of the hood static pressure method and (2) a severely modified version of the "Check-out" method. Three proposed pressure ratio methods also were evaluated and compared with the traditional methods. Two full-sized experimental ventilation systems in two ventilation laboratories were tested. One system had five branch ducts, the other had eight, with branch duct diameters ranging from 4 to 7 inches. To create challenge, each system received multiple alterations and, in some cases, the airflow level was changed throughout the system. For each round of measurements (1) different combinations of alterations were made to some ducts; (2) on a given system, relevant pressures and flows were determined for each duct using calibrated pressure sensors and standard pitot tubes held in a traversing device; and (3) the numbers of true and false positives and negatives for each screening method were computed for a broad range of threshold values. Sensitivities were plotted against the false positive rates for all thresholds for each method. The area (AROC) under the resulting "receiver operating characteristic curves" was computed for each method. Variability was simulated using bootstrap methods to determine significance of differences. In addition, the thresholds that would achieve 10 and 20% false positive rates were determined for each method and the accompanying sensitivities compared. The pressure ratio methods detected nearly all nontrivial obstructions with nearly zero false positives (AROC=1). The direct pressure comparison methods showed substantially inferior performance for the substantial challenges presented in these tests. The latter may be useful under less challenging conditions but were of dubious utility in locating obstructions under the ranges of conditions tested.