Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycl...Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.展开更多
The shear strength of gas-hydrate-bearing reservoirs is one of the most important parameters used to study mechanical properties of gas-hydrate-bearing reservoirs. The shear strength of gas-hydrate- bearing reservoirs...The shear strength of gas-hydrate-bearing reservoirs is one of the most important parameters used to study mechanical properties of gas-hydrate-bearing reservoirs. The shear strength of gas-hydrate- bearing reservoirs changes with filling and cementation of gas hydrates, which will affect the wellbore and reservoir stability. Traditional shear tests could not be conducted on gas-hydrate-bearing core samples because the gas hydrates exist under a limited range of temperature and pressure conditions. This paper describes a novel shear apparatus for studying shear strength of gas-hydrate-bearing core samples under original reservoir conditions. The preparation of gas-hydrate-bearing core samples and subsequent shear tests are done in the same cell. Cohesion and internal friction angle of the core samples with different saturations of gas hydrates were measured with the apparatus. The effect of gas hydrates on the shear strength of reservoirs was quantitatively analyzed. This provides a foundation for studying wellbore and reservoir stability of gas-hydrate-bearing reservoirs.展开更多
The method to calculate rock pressure to which the lining structure of tunnel with shallow depth is subjected in geologically inclined bedding strata is analyzed and put forward. Both the inclination angle of bedding ...The method to calculate rock pressure to which the lining structure of tunnel with shallow depth is subjected in geologically inclined bedding strata is analyzed and put forward. Both the inclination angle of bedding strata as well as the internal friction angle of bedding plane and its cohesion all exert an influence upon the magnitude of the asymmetric rock pressure applied to tunnel. The feature that rock pressure applied to tunnel structure varies with the incUnation angle of bedding strata is discussed, At last, the safety factor, which is utilized to evaluate the working state of tunnel lining structure, is calculated for both symmetric and asymmetric lining structures. The calculation results elucidate that the asymmetric tunnel structure can be more superior to bear rock pressure in comparison with the symmetric one and should be adopted in engineering as far as possible.展开更多
Following a rice or wheat harvest, a large amount of crop residue （straw） is retained in fields. The straw is often incorporated into the soil in order to increase the soil organic carbon storage and to reduce soil ...Following a rice or wheat harvest, a large amount of crop residue （straw） is retained in fields. The straw is often incorporated into the soil in order to increase the soil organic carbon storage and to reduce soil erosion. However, it has become apparent that the incorporated straw can significantly alter soil shear properties, which can dramatically affect energy inputs for tilling and other soil management practices. In this study, laboratory-remolded wheat straw-soil samples were compared with field-collected straw-soil samples; we found high correlations for the cohesion （R2=0.9084） and internal friction angle （R2=0.9548） properties of the samples. Shear tests on rice and wheat straw with different moisture content levels clearly demonstrated the relatively higher shear strength of wheat straw compared to rice straw. The cohesion of remolded rice and wheat straw-soil samples exhibited an increasing linear trend with an increase in densities, whereas the internal friction angle data for these samples exhibited a quadratic trend. Overlapping the cohesion curves revealed that the wheat straw-soil and rice straw-soil samples had the same cohesion at a straw density of 0.63%. Similar results were obtained when the internal fraction angle curves overlapped; the resultant point of intersection was observed at a straw density of 0.46%. As a whole, the remolded sample methodology was found suitable to simulate the shear properties of soils sampled directly from fields.展开更多
<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a struc...<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a structure represents the essential structural part of it, because it ensures its bearing capacity. Among the types of foundation, </span><span style="font-family:Verdana;">deep</span><span style="font-family:Verdana;"> foundation is the one for which from a mechanical point of view, the justification takes into account the isolated or combined effects of base resistance offered by the soil bed and lateral friction at the soil-pile interface;the latter being the consequence of a large contact surface with the surrounding soil;hence the need to study the interaction between the soil and the pile in service, in order to highlight the characteristics of soil which influence the mechanical behavior of pile and therefore the stability of the structure. In this study,</span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the reinforced concrete pile is supposed to be </span><span style="font-family:Verdana;">elastic,</span><span style="font-family:Verdana;"> and characterized by a young’s modulus (</span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">) and a Poisson’s ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">ν</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). The soil obeys to a Camclay model characterized by </span><span style="font-family:Verdana;">a cohesion</span><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;">), an initial voids ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Ver展开更多
One of the important issues for geotechnical engineers is the characterization of soil properties such as cohesion and internal friction angle by means of soil testing. A new experimental method of soil characterizati...One of the important issues for geotechnical engineers is the characterization of soil properties such as cohesion and internal friction angle by means of soil testing. A new experimental method of soil characterization based on the surface displacement of strip loaded soils is proposed. The theory to relate the soil deformation/displacement to soil strength properties is presented and compared with a series of conventional soil characterization techniques with direct shear tests. The proposed/developed strip loading tests provide reasonably accurate results compared with traditional direct shear tests. The new strip loading physical simulation and testing devices are helpful for understanding soil strength concepts and also provide an effective bridge connecting with engineering mechanics and foundation engineering courses instructions wherein derivation of bearing capacity theory equations is based on the same MohrCoulomb soil strength parameters. The advantages, limitations, and use of the strip loading modeling/testing technique in engineering education and further more in depth researches are discussed in the concluding remarks part.展开更多
Conjunction occupies an important part in discourse analysis, especially in the connecting analysis. The application of conjunction can achieve cohesion. However, according to the definition of register and genre, it ...Conjunction occupies an important part in discourse analysis, especially in the connecting analysis. The application of conjunction can achieve cohesion. However, according to the definition of register and genre, it is hard to find the total or completed function of these conjunctions in press release. The reason why this kind of phenomenon comes cross should be discussed in this paper. For doing this research, the researcher chooses one discourse which was found at www. globaleducationfirst.com as the material and select the conjunction out to prove the function of connection in application. As a kind of research, the aim or target is more important because as all paper goes, the purpose should be concentrated on. Why a style like news broadcasting or press release has so little conjunction functions as, for example, addition, means and, or contradictive but, however, and yet, or condition/f and so on. Some of them functions as internal, but others external. Whether it is the deliberate consideration or free formation by the editor is finally should be discussed, and from this point of view, conjunction＇ s function in press release reaches the target of cohesion展开更多
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2018D12National Natural Science Foundation of Heilongjiang Province under Grant No.E 2016045+1 种基金National Natural Science Foundation of China under Grant No.5137816451508140
文摘Using a new low-temperature dynamic triaxial apparatus, the influence law of freezing-thawing cycles on clay shear strength is studied. In this research, the concept of correction coefficients of freezing-thawing cycles on clay static strength, cohesion and internal friction angles is proposed, and the change patterns, correction curves and regressive formulae of clay static strength, cohesion and internal friction angles under freezing-thawing cycles are given. The test results indicate that with increasing numbers of freezing-thawing cycles, the clay static strength and cohesion decrease exponentially but the internal friction angle increases exponentially. The performance of static strength, cohesion and internal friction angles are different with increasing numbers of freezing-thawing cycles, i.e., the static strength decreases constantly until about 30% of the initial static strength prior to the freezing-thawing cycling and then stays basically stable. After 5-7 freezing-thawing cycles, the cohesion decreases gradually to about 70% of the initial cohesion. The internal friction angle increases about 20% after the first freezing-thawing cycle, then increases gradually close to a stable value which is an increase of about 40% of the internal friction angle. The freezing-thawing process can increase the variation of the density of the soil samples; therefore, strict density discreteness standards of frozen soil sample preparation should be established to ensure the reliability of the test results.
基金support from"Preliminary Research on natural gas hydrates production"from SINOPEC(No.P06070)
文摘The shear strength of gas-hydrate-bearing reservoirs is one of the most important parameters used to study mechanical properties of gas-hydrate-bearing reservoirs. The shear strength of gas-hydrate- bearing reservoirs changes with filling and cementation of gas hydrates, which will affect the wellbore and reservoir stability. Traditional shear tests could not be conducted on gas-hydrate-bearing core samples because the gas hydrates exist under a limited range of temperature and pressure conditions. This paper describes a novel shear apparatus for studying shear strength of gas-hydrate-bearing core samples under original reservoir conditions. The preparation of gas-hydrate-bearing core samples and subsequent shear tests are done in the same cell. Cohesion and internal friction angle of the core samples with different saturations of gas hydrates were measured with the apparatus. The effect of gas hydrates on the shear strength of reservoirs was quantitatively analyzed. This provides a foundation for studying wellbore and reservoir stability of gas-hydrate-bearing reservoirs.
文摘The method to calculate rock pressure to which the lining structure of tunnel with shallow depth is subjected in geologically inclined bedding strata is analyzed and put forward. Both the inclination angle of bedding strata as well as the internal friction angle of bedding plane and its cohesion all exert an influence upon the magnitude of the asymmetric rock pressure applied to tunnel. The feature that rock pressure applied to tunnel structure varies with the incUnation angle of bedding strata is discussed, At last, the safety factor, which is utilized to evaluate the working state of tunnel lining structure, is calculated for both symmetric and asymmetric lining structures. The calculation results elucidate that the asymmetric tunnel structure can be more superior to bear rock pressure in comparison with the symmetric one and should be adopted in engineering as far as possible.
基金financially supported by the National Natural Science Foundation of China (51275250)
文摘Following a rice or wheat harvest, a large amount of crop residue （straw） is retained in fields. The straw is often incorporated into the soil in order to increase the soil organic carbon storage and to reduce soil erosion. However, it has become apparent that the incorporated straw can significantly alter soil shear properties, which can dramatically affect energy inputs for tilling and other soil management practices. In this study, laboratory-remolded wheat straw-soil samples were compared with field-collected straw-soil samples; we found high correlations for the cohesion （R2=0.9084） and internal friction angle （R2=0.9548） properties of the samples. Shear tests on rice and wheat straw with different moisture content levels clearly demonstrated the relatively higher shear strength of wheat straw compared to rice straw. The cohesion of remolded rice and wheat straw-soil samples exhibited an increasing linear trend with an increase in densities, whereas the internal friction angle data for these samples exhibited a quadratic trend. Overlapping the cohesion curves revealed that the wheat straw-soil and rice straw-soil samples had the same cohesion at a straw density of 0.63%. Similar results were obtained when the internal fraction angle curves overlapped; the resultant point of intersection was observed at a straw density of 0.46%. As a whole, the remolded sample methodology was found suitable to simulate the shear properties of soils sampled directly from fields.
文摘<span style="font-family:Verdana;">This paper proposes a numerical simulation of the mechanical behavior of a reinforced concrete pile foundation under an axial load. In fact, the foundation of a structure represents the essential structural part of it, because it ensures its bearing capacity. Among the types of foundation, </span><span style="font-family:Verdana;">deep</span><span style="font-family:Verdana;"> foundation is the one for which from a mechanical point of view, the justification takes into account the isolated or combined effects of base resistance offered by the soil bed and lateral friction at the soil-pile interface;the latter being the consequence of a large contact surface with the surrounding soil;hence the need to study the interaction between the soil and the pile in service, in order to highlight the characteristics of soil which influence the mechanical behavior of pile and therefore the stability of the structure. In this study,</span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">the reinforced concrete pile is supposed to be </span><span style="font-family:Verdana;">elastic,</span><span style="font-family:Verdana;"> and characterized by a young’s modulus (</span><i><span style="font-family:Verdana;">E</span></i><span style="font-family:Verdana;">) and a Poisson’s ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">ν</span></i></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">). The soil obeys to a Camclay model characterized by </span><span style="font-family:Verdana;">a cohesion</span><span style="font-family:Verdana;"> (</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;">), an initial voids ratio (</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Ver
文摘One of the important issues for geotechnical engineers is the characterization of soil properties such as cohesion and internal friction angle by means of soil testing. A new experimental method of soil characterization based on the surface displacement of strip loaded soils is proposed. The theory to relate the soil deformation/displacement to soil strength properties is presented and compared with a series of conventional soil characterization techniques with direct shear tests. The proposed/developed strip loading tests provide reasonably accurate results compared with traditional direct shear tests. The new strip loading physical simulation and testing devices are helpful for understanding soil strength concepts and also provide an effective bridge connecting with engineering mechanics and foundation engineering courses instructions wherein derivation of bearing capacity theory equations is based on the same MohrCoulomb soil strength parameters. The advantages, limitations, and use of the strip loading modeling/testing technique in engineering education and further more in depth researches are discussed in the concluding remarks part.
文摘Conjunction occupies an important part in discourse analysis, especially in the connecting analysis. The application of conjunction can achieve cohesion. However, according to the definition of register and genre, it is hard to find the total or completed function of these conjunctions in press release. The reason why this kind of phenomenon comes cross should be discussed in this paper. For doing this research, the researcher chooses one discourse which was found at www. globaleducationfirst.com as the material and select the conjunction out to prove the function of connection in application. As a kind of research, the aim or target is more important because as all paper goes, the purpose should be concentrated on. Why a style like news broadcasting or press release has so little conjunction functions as, for example, addition, means and, or contradictive but, however, and yet, or condition/f and so on. Some of them functions as internal, but others external. Whether it is the deliberate consideration or free formation by the editor is finally should be discussed, and from this point of view, conjunction＇ s function in press release reaches the target of cohesion
