scholarly journals Development and operation of an automatic air pluviation system for physical modelling applications

2021 ◽  
pp. 1-41
Author(s):  
Jinbiao Wu ◽  
George Kouretzis ◽  
Jubert Pineda ◽  
Laxmi Suwal ◽  
Ross Gibson ◽  
...  
Keyword(s):  
Pressure Sensors ◽  
Earth Pressure ◽  
Physical Modelling ◽  
Deposition Process ◽  
Dense Sand ◽  
Cone Penetration Testing ◽  
Deposition Parameters ◽  
Tip Resistance ◽  
Time Required ◽  
Sand Beds

This paper presents an air pluviation system, developed to facilitate 1-g physical model tests in granular soils. The deposition process is fully automated and requires minimal input from the operator, thereby significantly reducing the time required to deposit large volume of granular material, improving the uniformity of the prepared specimens, and the reliability of test results. The components comprising the pluviation system have been calibrated to produce loose-to-very dense sand beds, of relative density that ranges between Dr=7% and Dr>100% of the maximum density achieved with the procedures described in the pertinent standards. The testing chamber where sand is deposited is instrumented with an array of pressure sensors, and the rig is equipped with a miniature Cone Penetration Testing (mini-CPT) device. Measurements from the earth pressure sensors and cone tip resistance profiles are used to evaluate how friction at the sand-chamber interfaces affects the distribution of geostatic stresses inside the chamber, the uniformity of sand beds, and boundary effects during deposition and during mini-CPT testing. The air pluviation system allows preparing layered sand profiles by adjusting the deposition parameters on the fly, and this feature is demonstrated via the analysis of mini-CPT tests performed in layered sand beds.

scholarly journals Working Mechanism of Pile Group with Different Pile Spacing in Dense Sand

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Yadong Chen ◽  
Fan Lu ◽  
Abdoullah Namdar ◽  
Jiangdong Cai
Keyword(s):  
Three Dimensional ◽  
Interaction Mechanism ◽  
Pile Group ◽  
Resistance Pattern ◽  
Pile Groups ◽  
Pile Spacing ◽  
Dense Sand ◽  
Energy Mechanism ◽  
Tip Resistance ◽  
Displacement Zone

Complex interaction mechanism exists between the pile group and soil. To realize the pile-soil load transmission mechanism in detail, the failure pattern of pile groups installed in dense sand considering different pile spacing was investigated by means of laboratory experimental model test and three-dimensional discrete element method. The results suggested that the narrow pile spacing was beneficial to the development of the pile tip resistance, and it enhanced the bearing performance of the pile group at the initial stage of settlement. The pile spacing changed the shaft resistance pattern with modification of the strain energy mechanism released within the subsoil. The pile group with 6b pile spacing had higher composite group efficiency. A joint fan-shaped displacement zone was formed beneath the pile tip for the pile group with 3b pile spacing; this pile foundation presented the block failure mechanism. The sand displacement beneath the cap for the pile group with 6b pile spacing mainly located on the upper part of the piles, the sand displacement around both sides of the piles presented asymmetric, and a relatively independent fan-shaped displacement zone was formed beneath the pile tip.

FBG Earth Pressure Sensors Applied in Surrounding Rock Pressure of Tunnel

2013 ◽  
Vol 351-352 ◽  
pp. 1173-1178
Author(s):  
Zhou Chun Cai ◽  
Chuan Li ◽  
Yuan Yu Guan ◽  
Wu Fen Chen ◽  
Li Jun Guo ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Rock Pressure ◽  
Pressure Sensors ◽  
Earth Pressure ◽  
Surrounding Rock ◽  
Bragg Grating ◽  
Wavelength Shift ◽  
Stress Changes ◽  
Surrounding Rock Pressure

During the period of tunnel excavation, shoring, forming and long-term operation, stress changes of tunnel surrounding rock are complex, the real-time monitoring of surrounding rock pressure is the key factor in ensuring long-term stability in tunnel. Fiber Bragg grating earth pressure sensors apply in surrounding rock pressure of tunnel which can change the pressure of the surrounding rock into fiber Bragg grating wavelength shift. According to the feature of pressure and temperature in Tian Xin Tunnel, 40 earth pressure sensors are embedded in 20 representative sections and one earth pressure sensor is embedded in each arch shoulder. In addition, one temperature compensation sensor is embedded in each arch crown. During the 235 monitoring days, the biggest daily change of surrounding rock pressure reaches 800 KPa. In 3 months of the sensor installation, the average monthly variation is within 50 KPa. The long-term measurement results indicate that the changes of surrounding rock pressure are different in different locations. When the surrounding rock is close to the excavated and blasted surface the surrounding rock pressure changes largely.

Full-scale shake table investigation of bridge abutment lateral earth pressure

2009 ◽  
Vol 42 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Patrick Wilson ◽  
Ahmed Elgamal
Keyword(s):  
Large Scale ◽  
Dynamic Pressure ◽  
Inertial Force ◽  
Earth Pressure ◽  
Shake Table ◽  
Passive Force ◽  
Dense Sand ◽  
Lateral Earth Pressure ◽  
Bridge Abutment ◽  
Force Displacement

During strong seismic excitation, passive earth pressure at the abutments may provide resistance to longitudinal displacement of the bridge deck. The dynamic pressure component may also contribute to undesirable abutment movement or damage. Current uncertainty in the passive force-displacement relationship and in the dynamic response of abutment backfills continues to motivate large-scale experimentation. In this regard, a test series is conducted to measure static and dynamic lateral earth pressure on a 1.7 meter high bridge abutment wall. Built in a large soil container, the wall is displaced horizontally into the dense sand backfill, in order to record the passive force-displacement relationship. The wall-backfill system is also subjected to shake table excitation. In the conducted tests, lateral earth pressure on the wall remained close to the static value during the low to moderate shaking events (up to about 0.5g). At higher levels of input acceleration, a substantial portion of the backfill inertial force started to clearly act on the wall.

FIELD EMISSION FROM CARBON FILMS GROWN BY THE CATHODIC ARC PROCESS

2000 ◽  
Vol 14 (02n03) ◽  
pp. 301-307 ◽  
Author(s):  
W. I. MILNE ◽  
J. ROBERTSON ◽  
B. S. SATYANARAYANA ◽  
A. HART
Keyword(s):  
Field Emission ◽  
Room Temperature ◽  
Deposition Process ◽  
Carbon Films ◽  
Deposition Parameters ◽  
Bonding Ratio ◽  
Cluster Beams ◽  
Cathodic Arc ◽  
Tetrahedrally Bonded

By using the catholic vacuum are deposition process, carbon films with variable sp 3/ sp 2 bonding ratio can be deposited on a variety of substrates at room temperature. The morphology of the films can be varied from the mirror like smooth tetrahedrally bonded carbon (ta-C) films through nanocluster to fibrous type carbon by altering the deposition parameters. This paper reviews the work carried out on Field Emission from such carbon films and compares the results with those on nanocluster films prepared using supersonic cluster beams. Threshold fields as low as 1 V /μ m with emission site densities of up to 104-105/ cm 2 have been obtained.

Development and Verification of Carbon Fiber Based FBG Earth Pressure Sensors Using Additive Manufacturing Technology

2020 ◽  
Vol 40 (21) ◽  
pp. 2106002
Author(s):  
鲍成志 Bao Chengzhi ◽  
洪成雨 Hong Chengyu ◽  
孙德安 Sun Dean ◽  
苏栋 Su Dong
Keyword(s):  
Additive Manufacturing ◽  
Carbon Fiber ◽  
Pressure Sensors ◽  
Earth Pressure ◽  
Manufacturing Technology ◽  
Additive Manufacturing Technology

Elastic Properties of Diamond Like Carbon Thin Films: a Brillouin Scattering Study

1996 ◽  
Vol 444 ◽  
Author(s):  
O. R. Monteiro ◽  
I. G. Brown ◽  
R. Sooryakumar ◽  
M. Chirita
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Elastic Constants ◽  
Brillouin Scattering ◽  
Deposition Process ◽  
Hard Coatings ◽  
Vacuum Arc ◽  
Deposition Parameters ◽  
Scattering Study ◽  
Isotropic Solids

AbstractDiamondlike carbon (DLC) thin films have been widely used as hard coatings in a variety of applications where increased wear resistance and hardness are required. Vacuum arc DLC films are among the hardest, with measured hardness values of up to 68 GPa. In our deposition process a repetitively pulsed bias voltage is applied to the substrate, which controls the energy of the incoming C ions. DLC chemical and mechanical properties are strongly affected by the energy of the depositing ions. In this paper, we relate the mechanical properties of these films to the deposition parameters, and describe our initial Brillouin scattering measurements of the elastic constants of monolithic DLC films. Evidence for bulk longitudinal and surface Rayleigh excitation in films with thickness of 50 and 500 nm has been observed. Since the DLC films are amorphous, they are modeled as isotropic solids and the elastic constants CII and C44 are derived.

Scale Model Investigations on Vibro Pile Driving

2018 ◽  
Author(s):  
Philipp Stein ◽  
Nils Hinzmann ◽  
Jörg Gattermann
Keyword(s):  
Penetration Depth ◽  
Earth Pressure ◽  
Offshore Wind ◽  
Scale Model ◽  
Pile Driving ◽  
Scaled Model ◽  
Dense Sand ◽  
Pressure Transducers ◽  
Vibration Technique ◽  
Force Equilibrium

Monopiles installed by impact driving are the preferred system for the foundation of offshore wind turbines in water depths up to 40 m. The vibration technique as alternative installation method has big advantages regarding piling noise and installation time. Much experience exists for the design and installation of impact driven piles. Within the research project ZykLaMP, the lack of experience concerning vibrated monopiles shall be faced by means of large-scaled model investigations regarding the lateral load-bearing behavior. Therefore, open ended steel pipe piles (L = 2.4 m, Dpile = 0.6 m) are installed into dense sand by means of impact and vibratory pile driving and then subjected to cyclic lateral loading. This paper focusses on pile driving predictions and measurements during the installation process. Pile driving post-predictions were carried out based on a simple force equilibrium approach. Model piles were installed using two different vibro hammers with different eccentric moments and one impact hammer. Measurements of strains and accelerations were carried out to investigate dynamic movements during pile driving. Earth pressure transducers were used to investigate the development of soil stresses due to the installation process. Measurements show that even at high acceleration amplitudes a refusal to vibratory driving may occur at a certain penetration depth. Soil stresses in the vicinity of the pile decrease to about 50 % due to vibratory driving which is one reason for the friction fatigue phenomenon. Drivability studies using the force equilibrium model give rough predictions about whether or not a pile can be driven to a certain penetration depth but are quite sensitive to input parameters. For the model tests, post-predictions gave reasonable results.

Influence of placement method on the cone penetration resistance of hydraulically placed sand fills

2001 ◽  
Vol 38 (3) ◽  
pp. 592-607 ◽  
Author(s):  
K M Lee
Keyword(s):  
Cone Penetration ◽  
Density Profiles ◽  
Hydraulic Fill ◽  
Dense Sand ◽  
Cone Penetration Tests ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Wide Range ◽  
Penetration Tests

The reclamation for the new airport at Chek Lap Kok in Hong Kong included the placement of a substantial volume of sand fill by various hydraulic placement techniques, which resulted in a wide range of as-placed densities of the sand fill. This paper described the use of cone penetration tests (CPT) on the evaluation of the possible ranges of density achievable by various hydraulic placement methods adopted in the construction of the new airport. The results of the CPT indicated that the placement technique is one of the most important factors in controlling the as-placed density of hydraulically placed sand fill. There is a marked contrast in cone tip resistance (and the associated relative density) profiles for the sand fills formed by subaerial and subaqueous placement methods, in which the cone tip resistance of the sand fill formed by subaerial placement is substantially higher than that of the sand fill formed by subaequeous placement. The results confirm that dense sand fill cannot be formed by subaqueous placement methods. The weakest zone is generally located just beneath the water level where fill is placed by subaqueous discharge.Key words: sand, hydraulic fill, cone penetration test, calibration chamber test, in situ density.

Influence of Deposition Parameters on the Properties of Nanocomposite Coatings Prepared by Cathodic Arc Evaporation

2016 ◽  
Vol 368 ◽  
pp. 77-81
Author(s):  
Miroslav Béger ◽  
Jozef Sondor ◽  
Martin Sahul ◽  
Paulína Zacková ◽  
Marián Haršáni ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Bias Voltage ◽  
Deposition Process ◽  
Gas Pressure ◽  
Nanocomposite Coatings ◽  
Evaporation Process ◽  
Deposition Parameters ◽  
Cathodic Arc Evaporation ◽  
Arc Evaporation ◽  
Cathodic Arc

The article deals with the influence of different deposition parameters on the selected properties of AlCrN/Si3N4 nanocomposite coatings. Bias voltage, cathodes currents and working gas pressure were changed during the deposition process. All coatings were deposited using Lateral Rotating Cathodes (LARC®) process that belongs to the group of cathodic arc evaporation PVD technologies. In comparison with the typical cathodic arc evaporation process which usually uses planar targets the LARC® process utilizes rotational cathodes that are positioned close to each other. Nanohardness, Young's modulus, thickness and residual stresses were determinated in order to evaluate the influence of deposition parameters on these coatings properties

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