scholarly journals Water Transport in Unsaturated Cracked Concrete under Pressure

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Yuanzhu Zhang ◽  
Siming Zhang ◽  
Gang Wei ◽  
Xinjiang Wei ◽  
Liqiao Jin ◽  
...  
Keyword(s):  
Water Transport ◽  
Driving Force ◽  
Crack Width ◽  
Water Pressure ◽  
Theoretical Models ◽  
Double Porosity ◽  
Hydraulic Pressure ◽  
Pressure Potential ◽  
Cracked Concrete ◽  
Concrete Permeability

In order to analyze the process of hydraulic water infiltrating cracked concrete of underwater tunnels, the equation of water transport in unsaturated cracked concrete under pressure was proposed according to the double-porosity medium model. Penetration tests on prefabricated cracked concrete blocks were conducted, and then the influence of hydraulic pressure, initial saturation, and crack width on water transport was studied. The results show that the larger the water pressure, the lower the initial saturation, and the wider the crack width, then the greater the penetration depth, which can be reasonably explained according to water motion theoretical models in this study. Moreover, the TOUGH2 software was used to simulate the change and distribution of saturation, driving potential, and water velocity of unsaturated cracked concrete, which further proved the experimental results and theoretical analysis. It reflects that both pressure potential and matric potential are the driving force of water transport in underwater cracked concrete, and the driving force will be converted with the change of concrete saturation. In addition, crack width is positively correlated with concrete permeability.

scholarly journals Visualization and Quantification of the Penetration Behavior of Bentonite Suspensions into the Pore Network of non-cohesive Media by using μ-CT Imaging

2016 ◽  
Author(s):  
Britta Schoesser ◽  
Atefeh Ghorbanpour ◽  
Matthias Halisch ◽  
Markus Thewes
Keyword(s):  
Filter Cake ◽  
Pore Space ◽  
Water Pressure ◽  
Soft Soil ◽  
Theoretical Models ◽  
Bored Pile ◽  
Soil Skeleton ◽  
Bentonite Suspension ◽  
Penetration Behavior ◽  
Drill Holes

Abstract. Bentonite suspensions are an essential tool for different construction techniques in horizontal and vertical drilling, in diaphragm and bored pile walls as well as in pipe jacking and tunneling. One of the main tasks of the suspension is to prevent the surrounding ground from collapsing during the excavation process of trenches, drill holes or tunnels. In order to maintain the soil stability close to the excavation, the bentonite suspension has to counteract against the earth and water pressure. Therefore, the pressure acting in the suspension has to counter the groundwater pressure and to be transferred into an effective stress to support the soil skeleton. The creation of a pressure transfer mechanism can be achieved in two ways. A direct relation exists between the mechanism of the pressure transfer and the penetration behavior of the bentonite suspension in the subsoil. The relation of the size of the bentonite particles in the suspension and the size of the pores in soft soil is decisive. In addition, the yield strength of the bentonite suspension is a determining factor. Concerning the penetration behavior two theoretical models exist actually: formation of a filter cake and entire penetration into the pore space. If the pore space is smaller than the size of the bentonite particles, a filtration process takes place. Here, the bentonite particles agglomerate gradually at the entrance of the pore space and create a thin nearly impermeable layer. This membrane is named filter cake. If the pore space is larger than the size of the bentonite particles, the suspension penetrates into the subsoil up to a certain depth. These models have a more theoretical character due to missing visual evidence concerning the interaction of the bentonite suspension in the pore space. Here, the micro CT technique delivers a valuable contribution to this research.

Determination of Permeability Properties of Concrete Surface Modified by CPF

2015 ◽  
Vol 732 ◽  
pp. 389-392 ◽  
Author(s):  
Pavel Reiterman
Keyword(s):  
Surface Layer ◽  
Water Transport ◽  
Concrete Surface ◽  
Experimental Results ◽  
Experimental Program ◽  
Functional Characteristics ◽  
Concrete Permeability ◽  
Surface Modified ◽  
Durability Of Concrete

The paper introduces an experimental program focused on the monitoring of water transport in surface layer of concrete aimed at monitoring the permeability of concrete, since concrete permeability is a property uniquely affecting durability of concrete. Introduced methods are complemented by experimental results and other traditional tests. These findings will serve to further optimization of the structure being created, thus ensuring its better aesthetic and functional characteristics.

scholarly journals Effect of Ionic Radius in Metal Nitrate on Pore Generation of Cellulose Acetate in Polymer Nanocomposite

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 981
Author(s):  
Woong Gi Lee ◽  
Younghyun Cho ◽  
Sang Wook Kang
Keyword(s):  
Cellulose Acetate ◽  
Ionic Radius ◽  
Water Pressure ◽  
Water Flux ◽  
Atomic Radius ◽  
Ionic Species ◽  
Metal Nitrate ◽  
Hydraulic Pressure ◽  
Physical Force ◽  
Nitrate Salts

To prepare a porous cellulose acetate (CA) for application as a battery separator, Cd(NO3)2·4H2O was utilized with water-pressure as an external physical force. When the CA was complexed with Cd(NO3)2·4H2O and exposed to external water-pressure, the water-flux through the CA was observed, indicating the generation of pores in the polymer. Furthermore, as the hydraulic pressure increased, the water-flux increased proportionally, indicating the possibility of control for the porosity and pore size. Surprisingly, the value above 250 LMH (L/m2h) observed at the ratio of 1:0.35 (mole ratio of CA: Cd(NO3)2·4H2O) was of higher flux than those of CA/other metal nitrate salts (Ni(NO3)2 and Mg(NO3)2) complexes. The higher value indicated that the larger and abundant pores were generated in the cellulose acetate at the same water-pressure. Thus, it could be thought that the Cd(NO3)2·4H2O salt played a role as a stronger plasticizer than the other metal nitrate salts such as Ni(NO3)2 and Mg(NO3)2. These results were attributable to the fact that the atomic radius and ionic radius of the Cd were largest among the three elements, resulting in the relatively larger Cd of the Cd(NO3)2 that could easily be dissociated into cations and NO3− ions. As a result, the free NO3− ions could be readily hydrated with water molecules, causing the plasticization effect on the chains of cellulose acetate. The coordinative interactions between the CA and Cd(NO3)2·4H2O were investigated by IR spectroscopy. The change of ionic species in Cd(NO3)2·4H2O was analyzed by Raman spectroscopy.

Pore-morphology-based simulations of drainage and wetting processes in porous media

2011 ◽  
Vol 42 (2-3) ◽  
pp. 128-149 ◽  
Author(s):  
T. P. Chan ◽  
Rao S. Govindaraju
Keyword(s):  
Porous Media ◽  
Hydraulic Properties ◽  
Pore Space ◽  
Water Pressure ◽  
Theoretical Models ◽  
Hysteretic Behavior ◽  
Water Retention Curve ◽  
Pore Morphology ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic

Soil hydraulic properties relating saturation, water pressure, and hydraulic conductivity are known to exhibit hysteresis. In this paper, we focus on the determination of the water retention curve for a porous medium through a novel pore-scale simulation technique that is based on mathematical morphology. We develop an algorithm that allows for the representation of three-dimensional randomly packed porous media of any geometry (i.e. not restricted to idealized geometries such as spherical or ellipsoidal particles/pore space) so that the connectivity-, tortuosity-, and hysteresis-causing mechanisms are represented in both drainage and wetting processes, and their role in determining macroscopic fluid behavior is made explicit. Using this method, we present simulation results that demonstrate hysteretic behavior of wetting and non-wetting phases during both drainage and wetting cycles. A new method for computing interfacial surface areas is developed. The pore-morphology-based method is critically evaluated for accuracy, sample size effects, and resolution effects. It is found that the method computes interfacial areas more accurately than existing methods and allows for (i) examination of relationships between water pressure, saturation and interfacial area for hysteretic soils, and (ii) comparisons with previously developed theoretical models of soil hydraulic properties. The pore-morphology-based method shows promise for applications in vadose zone hydrology.

Evaluating the Potential for Damaging Hydraulic Pressure in the Concrete Tie Rail Seat

2010 ◽  
Author(s):  
John C. Zeman ◽  
J. Riley Edwards ◽  
David A. Lange ◽  
Christopher P. L. Barkan
Keyword(s):  
Surface Water ◽  
Effective Stress ◽  
Water Pressure ◽  
Hydraulic Pressure ◽  
Vertical Load ◽  
Critical Problem ◽  
Surface Geometry ◽  
State Of Stress ◽  
Pore Water Pressures ◽  
Prestressed Beam

Rail seat deterioration (RSD) is the most critical problem with concrete tie performance on North American freight railroads. Currently, the problem is not sufficiently understood to allow for effective solutions. RSD is considered to have up to five potential mechanisms, and this paper investigates one of them: hydraulic pressure cracking. A model of the effective stress in a concrete tie rail seat — considering the contributions of a uniform vertical load, a uniform lateral load, a prestressed beam on an elastic foundation, and pore pressure to the state of stress — was created to determine what surface water pressures at the rail seat could lead to damaging pore water pressures in the concrete. A laboratory test setup and procedure were devised to measure the surface water pressure in a laboratory rail seat using tie pads of differing material composition and geometry. Results show that the magnitude of the pressure generated and the rate of pressure dissipation with many load cycles depends on the pad material and surface geometry. Comparing the effective stress model and the measured surface pressures, hydraulic pressure cracking appears to be a feasible mechanism for RSD given the correct combination of dynamic rail seat loads, sufficient moisture, and a tie pad surface that develops high pressure.

Performance of the Inducing Joints in Xiaowan Arch Dam with Reservoir Impounded to Normal Water Level

2013 ◽  
Vol 405-408 ◽  
pp. 511-520
Author(s):  
Zheng Chao Lu ◽  
Li Bing Li ◽  
Feng Shang ◽  
Yun Hui Jiang
Keyword(s):  
Water Level ◽  
Crack Width ◽  
Water Pressure ◽  
Safety Monitoring ◽  
Arch Dam ◽  
Joint Surface ◽  
Close Attention ◽  
Normal Water ◽  
Small Cracks ◽  
The Right

To reduce the tensile stress at dam heel, inducing joints have been set in Xiaowan arch dam; they were designed to work without water pressure. After the reservoir was impounded to the normal water level of E.L.1240m, monitoring data showed that almost half of the inducing joints were working with water pressure, but leakage remained small. It also indicated the opening and shear deformation of all the inducing joints were small, and the joint surface remained in compression although the compressive stress was decreased by 2.03MPa~9.29MPa. So it can be concluded that the inducing joints are generally working at closing and compressive state. However, some abnormalities were detected: large seepage pressure and increasing crack width in block No.16 which is at the right end of the inducing joints; 5 small cracks appeared with leakage water at the downstream inner surface of the inspection gallery of the inducing joint in block No.22. Therefore, close attention has to be paid to the crack propagation around the inducing joints for the safety monitoring in future.

I.—Studies in Floral Morphology. II. The Staminal Zygomorphy of Couroupita guianensis, Aubl.

1922 ◽  
Vol 53 (1) ◽  
pp. 1-15 ◽  
Author(s):  
John M'Lean Thompson
Keyword(s):  
Water Pressure ◽  
Pollen Grains ◽  
Second Phase ◽  
Hydraulic Pressure ◽  
Developmental Study ◽  
Couroupita Guianensis ◽  
Dicotyledonous Plants ◽  
History Of ◽  
Floral Characters ◽  
Pollen Shed

In a former memoir published in these Transactions (20) the developmental study of floral characters has been reopened. It has there been shown that by this study, which for long has received little attention, the investigator, aided by modern technical methods, may gain a fuller understanding of the value of the characters by which his judgment in systematic matters is guided. The subject then dealt with was the initiation of staminal zygomorphy in certain dicotyledonous plants. It was there shown that in the history of a stamen from its initiation as a primordium until its anther is dehisced and its pollen shed there are three more or less distinct consecutive phases. In the first, or phase of initiation, the stamen-primordium is defined. From this primordium an undifferentiated multicellular body arises by rapid cell-division. In the second phase this body undergoes differentiation into the component parts of a stamen ; an anther and frequently a filament and connective are defined, and their cellular construction is completed. In the third and final phase the stamen is extended and functionates forthwith as a disseminator of pollen-grains. In this phase the extensible and elastic walls of the cells of the filament are distended by internal hydraulic pressure, and the anther-walls are dried and finally rupture by inequalities in their rate of shrinkage and by the agency of fibrous devices. These steps form the prelude to the actual functionating of the stamen, and since the final enlargement of the stamen-filament is due to water-pressure, this phase is known as the phase of extension.

Research on Seepage Field in Fractured Rock Mass of Underground Oil Storage Cave Using Distinct Element Method

2013 ◽  
Vol 353-356 ◽  
pp. 619-623
Author(s):  
Song Yu ◽  
Yun Peng Zhang ◽  
Wei Shen Zhu
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Distinct Element ◽  
Water Pressure ◽  
Hydraulic Pressure ◽  
Fractured Rock Mass ◽  
Water Curtain ◽  
Oil Storage ◽  
Underground Caverns ◽  
Element Method

The distribution of hydraulic pressure in fractured rock mass surrounding caverns after excavation and technique of stochastic generation of joint network are investigated based on discrete element method. In order to seal the oil in underground caverns with water in the actual engineering, a water curtain with water pressure is installed, and the changes of hydraulic pressure are simulated with a series of curtain pressures. It is shown that some joints that have been drained out during excavation can not be saturated if the water curtain pressure is less than a certain value. Water curtain pressure with a certain value gives a strong safe guarantee of saving oil in the underground petroleum storage caverns.

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