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Auckpath Sawangsuriya - One of the best experts on this subject based on the ideXlab platform.
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laboratory and field evaluation of modulus Suction moisture relationship for a silty sand subgrade
Transportation geotechnics, 2019Co-Authors: Rizki Maretia Novi Barus, Apiniti Jotisankasa, Susit Chaiprakaikeow, Auckpath SawangsuriyaAbstract:Abstract A change in soil modulus in response to Suction-moisture variation after compaction plays a vital role on modulus-based compaction control during earthwork construction. This study investigated the small-strain modulus-Suction-moisture relationship for a silty sand subgrade using the laboratory free-free resonant frequency (FFR) and the in-situ spectral analysis of surface waves (SASW) in a trial section of highway construction project in Thailand. The post-compaction soil water retention curves (SWRCs) at different compaction states were investigated over the entire range of Suction. Relationships between the SWRC parameters, i.e., air-entry Suction, water-entry Suction, residual Suction etc., and as-compacted dry density and water content were obtained using the multiple-linear regression analysis. Such relationships are useful for the prediction of post-compaction Suction in the field. The variation of SASW and FFR shear moduli with the Suction stress, inferred from SWRCs, was found to be linear. A modified model was proposed, considering the combined effect of void ratio and the Suction stress on the shear modulus, represented as Parameter A which was found to decrease as Suction increased. The inclusion of Suction stress and void ratio within the model variables yields better accuracy of prediction as compared to those models that considered either only Suction or water content.
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effect of Suction on resilient modulus of compacted fine grained subgrade soils
Transportation Research Record, 2009Co-Authors: Auckpath Sawangsuriya, Tuncer B Edil, Craig H BensonAbstract:Resilient modulus of compacted subgrade soils is the primary mechanical property required in the mechanistic-empirical design of pavement structures. In most cases, the resilient modulus is determined of a specimen prepared at a single compaction condition (i.e., near optimum water content and at a specified percentage of maximum dry unit weight). However, in the field, the resilient modulus changes in response to changes in moisture content and corresponding changes in matric Suction. The relationship between resilient modulus and Suction is described for four fine-grained compacted subgrade soils. Resilient modulus tests were conducted in accordance with NCHRP 1-28A on test specimens prepared from each soil and conditioned to different matric Suctions. The summary resilient modulus increases with increasing matric Suction. This relationship is quantified empirically by using a modulus ratio, defined as the ratio of the summary resilient modulus at a particular Suction to a reference summary resilient mo...
Eckhard A Groll - One of the best experts on this subject based on the ideXlab platform.
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study of ejector efficiencies in refrigeration cycles
Applied Thermal Engineering, 2013Co-Authors: Eckhard A GrollAbstract:Abstract This paper presents a method of determining internal ejector component efficiencies using a two-phase flow ejector model. The measured performance data external to the ejector in conjunction with the ejector model were used to determine the isentropic efficiencies of the motive and Suction nozzles, and the efficiency of mixing section. It was found that ejector component efficiencies vary with ejector geometries and operating conditions, which are different from the constant efficiencies assumed by previous researchers. The efficiencies of the controllable ejector motive nozzle, Suction nozzle and mixing section range from 0.50 to 0.93, from 0.37 to 0.90, and 0.50 to 1.00, respectively, in CO2 refrigeration cycles under different operating conditions. Empirical correlations were established and incorporated into a CO2 air conditioning system model to estimate ejector component efficiencies at different ejector geometries and operating conditions.
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investigation on performance of variable geometry ejectors for co2 refrigeration cycles
Energy, 2012Co-Authors: Eckhard A Groll, Daqing LiAbstract:This paper presents a comprehensive study on a controllable two-phase flow ejector component efficiencies and ejector performances in transcritical CO2 refrigeration cycles. A two-phase flow ejector expansion model was developed and experimentally validated. A method of determining the efficiencies of ejector motive nozzle, Suction nozzle, and mixing section based on the measured performance data external to the ejector was developed. It was found that motive nozzle efficiency decreases as ejector throat area decreases, and that Suction nozzle efficiency is affected by outdoor air temperature. Empirical correlations of ejector component efficiencies were reduced. Parametric modeling study results show that the operation of an ejector reaches its optimum performance at ejector throat diameter approximately of 2.3 mm, mixing section constant-area diameter approximately of 3.5 mm, and diffuser diameter ratio a little bit larger than 2. Higher efficiencies of motive nozzle and Suction nozzle as well as higher motive nozzle inlet pressure result in better ejector performances in certain ranges of motive nozzle throat diameter and mixing section constant-area diameter.
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investigation on performance of variable geometry ejectors for co refrigeration cycles
Energy, 2012Co-Authors: Fang Liu, Eckhard A GrollAbstract:Abstract This paper presents a comprehensive study on a controllable two-phase flow ejector component efficiencies and ejector performances in transcritical CO 2 refrigeration cycles. A two-phase flow ejector expansion model was developed and experimentally validated. A method of determining the efficiencies of ejector motive nozzle, Suction nozzle, and mixing section based on the measured performance data external to the ejector was developed. It was found that motive nozzle efficiency decreases as ejector throat area decreases, and that Suction nozzle efficiency is affected by outdoor air temperature. Empirical correlations of ejector component efficiencies were reduced. Parametric modeling study results show that the operation of an ejector reaches its optimum performance at ejector throat diameter approximately of 2.3 mm, mixing section constant-area diameter approximately of 3.5 mm, and diffuser diameter ratio a little bit larger than 2. Higher efficiencies of motive nozzle and Suction nozzle as well as higher motive nozzle inlet pressure result in better ejector performances in certain ranges of motive nozzle throat diameter and mixing section constant-area diameter.
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analysis of a two phase flow ejector for the transcritical co2 cycle
2008 Purdue Conferences. 19th International Compressor Engineering Conference at Purdue & 12th International Refrigeration and Air-Conditioning Confer, 2008Co-Authors: Fang Liu, Eckhard A GrollAbstract:This paper presents the analysis of a two phase flow ejector for the transcritical CO2 cycle. A detailed simulation model of a two phase flow ejector was developed. A controllable ejector expansion device was designed, constructed, and installed in a transcritical CO2 experimental air conditioning system. System-level experimental results were obtained at different operation conditions and various ejector geometries. The ejector expansion model was then utilized to determine the efficiencies of the motive nozzle, Suction nozzle, and mixing section using the system-level measured data. It was found that motive nozzle efficiency decreases as ejector throat area decreases and that the Suction nozzle efficiency is affected by the outdoor temperature and ejector throat area. In addition, the distance from the motive nozzle exit to the mixing section constant area entry not only affects the Suction nozzle efficiency, but also affects the mixing section efficiency.
Yutsung Tai - One of the best experts on this subject based on the ideXlab platform.
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variation of resilient modulus with soil Suction for compacted subgrade soils
Transportation Research Record, 2005Co-Authors: Shu Rong Yang, Wei Hsing Huang, Yutsung TaiAbstract:The variations of resilient modulus with the postconstruction moisture content and soil Suction for cohesive subgrade soils were evaluated. In particular, the effects of relative compaction of the subgrade on the Suction and resilient modulus were investigated. To simulate subgrade soils at in-service conditions, soil specimens were compacted at various relative compactions and optimum moisture content and then saturated to equilibrium moisture content to test for resilient modulus and soil Suction. The filter paper method was used to measure the total and matric Suctions of two cohesive soils. Test findings demonstrated that resilient modulus correlated better with the matric Suction than with total Suction. Matric Suction was found to be a key parameter for predicting the resilient modulus of cohesive subgrade soils. A prediction model incorporating deviator stress and matric Suction for subgrade soil resilient modulus was established.
Md Akhtar Hossain - One of the best experts on this subject based on the ideXlab platform.
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dilatancy and strength of an unsaturated soil cement interface in direct shear tests
International Journal of Geomechanics, 2015Co-Authors: Md Akhtar HossainAbstract:AbstractThe dilatancy of a soil is significantly influenced by matric Suction, and it affects the apparent friction angle and shear strength of the soil. To examine the influence of dilatancy on interface behavior, a series of direct shear box tests are conducted on a compacted completely decomposed granite (CDG) soil–grout interface in a cast in situ condition under different matric Suctions and net normal stresses. The test results indicate that matric Suction and net normal stress have significant influence on the hardening-softening and dilatancy of the soil–cement grout interface. The failure envelopes for different matric Suctions are observed as linear. The apparent interface friction angle and adhesion intercept increase with matric Suction. The Suction envelope is found to be nonlinear as the δb-angle decreases with matric Suction. A modified model is proposed to consider the influence of dilatancy on the apparent interface friction angle and hence on the interface shear strength. Experimental sh...
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influence of grouting pressure on the behavior of an unsaturated soil cement interface
Journal of Geotechnical and Geoenvironmental Engineering, 2012Co-Authors: Md Akhtar HossainAbstract:The strength of soil-nails depends on the behavior of the soil-cement grout interface at saturated and unsaturated conditions. Nowadays, pressure grouted soil-nails are considered to provide better interface strength than gravity grouted soil-nails. Soil-nail pullout tests have limitations to control some boundary conditions. To overcome these limitations, direct shear tests can be used to determine the actual soil-cement grout interface behavior. In the present study, a series of interface direct shear tests are performed between compacted completely decomposed granite (CDG) soil and cement grout at both saturated and unsaturated conditions under different grouting pressures. The inter- face shear stress increases with matric Suction for different grouting pressures, and a strain softening behavior is observed for different Suctions except at saturated conditions. A dilative behavior is obvious for interface as the Suctionvalue is increased from a saturated condition. However, the dilation values of soil-cement interface for different grouting pressures are less than that of CDG soil under different Suctions. The interface shear strength increases with grouting pressure at saturated conditions, whereas, a downward trend is obvious as the Suction value is increased from saturated conditions. The rate of increase of shear strength with matric Suction is greater for CDG soil compared to soil-cement interface. Interface shear strengths for different grouting pressures are greater than CDG soil at a lower Suction range but become less than CDG soil at a higher Suction range. DOI: 10.1061/(ASCE)GT.1943-5606.0000585. © 2012 American Society of Civil Engineers. CE Database subject headings: Grouting; Suction; Cement; Soil nailing; Unsaturated soils. Author keywords: Grouting pressure; Matric Suction; CDG soil; Cement grout; Interface; Direct shear.
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shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil
Canadian Geotechnical Journal, 2010Co-Authors: Md Akhtar HossainAbstract:Shear strength and dilative characteristics of a re-compacted completely decomposed granite (CDG) soil are studied by performing a series of single-stage consolidated drained direct shear tests under different matric Suctions and net normal stresses. The axis-translation technique is applied to control the pore-water and pore-air pressures. A soil-water retention curve (SWRC) is obtained for the CDG soil from the equilibrium water content corresponding to each applied matric Suction value for zero net normal stress using a modified direct shear apparatus. Shear strength increases with matric Suction and net normal stress, and the failure envelope is observed to be linear. The apparent angle of internal friction and cohesion intercept increase with matric Suction. A greater dilation angle is found at higher Suctions with lower net normal stresses, while lower or zero dilation angles are observed under higher net normal stresses with lower Suctions, also at a saturated condition. Experimental shear strength...
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behavior of a compacted completely decomposed granite soil from Suction controlled direct shear tests
Journal of Geotechnical and Geoenvironmental Engineering, 2010Co-Authors: Md Akhtar Hossain, Jianhua YinAbstract:A series of single-staged consolidated drained direct shear tests are carried out on recompacted completely decomposed granite (CDG) soil—a typical residual soil in Hong Kong, under different matric Suctions and net normal stresses. Matric Suction is controlled by applying air pressure in the pressure chamber and water pressure at the bottom of the high air-entry ceramic disk. The experimental results show that the contribution of Suction to shear strength is significant. Shear strength of CDG soil increases with the increase of matric Suction. Net normal stress has a remarkable influence on the shear strength of unsaturated CDG soil. The increase in shear strength due to an increase in matric Suction (Suction envelope) is observed as nonlinear i.e., ϕb value varies with matric Suction. No soil dilatancy is observed for zero matric Suction (saturated case) but as the Suction value is increased, higher soil dilatancy is obvious in lower net normal stresses. The rate of increase of soil dilatancy is greater...
Craig H Benson - One of the best experts on this subject based on the ideXlab platform.
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effect of Suction on resilient modulus of compacted fine grained subgrade soils
Transportation Research Record, 2009Co-Authors: Auckpath Sawangsuriya, Tuncer B Edil, Craig H BensonAbstract:Resilient modulus of compacted subgrade soils is the primary mechanical property required in the mechanistic-empirical design of pavement structures. In most cases, the resilient modulus is determined of a specimen prepared at a single compaction condition (i.e., near optimum water content and at a specified percentage of maximum dry unit weight). However, in the field, the resilient modulus changes in response to changes in moisture content and corresponding changes in matric Suction. The relationship between resilient modulus and Suction is described for four fine-grained compacted subgrade soils. Resilient modulus tests were conducted in accordance with NCHRP 1-28A on test specimens prepared from each soil and conditioned to different matric Suctions. The summary resilient modulus increases with increasing matric Suction. This relationship is quantified empirically by using a modulus ratio, defined as the ratio of the summary resilient modulus at a particular Suction to a reference summary resilient mo...