Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

Journal Issue Information

Archive

Year

Volume(Issue)

Issues

مرکز اطلاعات علمی SID1
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    17-174
Measures: 
  • Citations: 

    0
  • Views: 

    598
  • Downloads: 

    197
Abstract: 

Considering the fact that the estimation of mode fracture toughness by testing is time-consuming and expensive. It might be associated with certain practical difficulties. Therefore, many researchers have attempted to propose experimental relationships in order to capture these problems. Gunsallus et al. (1984) and Bhagat (1985) experimentally found that mode fracture toughness is related to tensile strength. Whittaker et al. (1992) have also proposed a number of relationships between mode I fracture toughness, tensile strength, point load index, uniaxial compressive strength and the velocity of sound waves. Bearman (1999) obtained an experimental relationship between mode I fracture toughness and point load index, while Brown et al. (1997) presented an experimental relationship between this parameter and density. Up to now no significant research effort has been made in this field in Iran, only Ayatollahi and Fatehi addressed rock fracture toughness. Although, Ayatollahi has not presented any experimental relationships. In the present research the three-point bending test was used on a cylindrical specimen containing a straight crack in order to determine the mode fracture toughness, and the Brazilian test was employed to determine tensile strength. Materials and Methods The tests were carried out on six types of rocks, namely gray sandstone, tuff, lithic tuff, travertine, andesite, and limestone. Sandstone, travertine, and limestone are sedimentary rocks, while andesite is an extrusive igneous rock, and tuff and lithic tuff are pyroclastic rocks (pyroclastic rocks resulting from volcanic eruptions that harden by sedimentation). Therefore, the studied rocks have different origins. In order to carry out the Brazilian and the three-point bending test, cores were prepared from these blocks. In order to perform the three-point bending test, specimens with diameter of 73 mm with a thickness of 30 mm were used. The samples were cut in two semicircular by a cutting machine, and a notch with length of 15 mm is created by a diamond saw. Notch is vertical in the center of the semicircular samples. The Brazilian test was performed on disc shaped specimens. In order to perform the Brazilian test, specimens with diameter of 51 mm and thick of 25 mm were used. The specimens are carefully placed under the curved jaws of the machine and then loaded until fracture. Results and Discussion A summary of the Brazilian and the three-point bending test results are presented in Table 1. The average value of test result pertaining to each rock is reported in Table 1. Table 1. Summary of the Brazilian and the three-point bending test results Specimen Tensile Strength (MPa) Fracture Toughness (MPa√ m) Limestone 3. 74 1. 23 Sandstone 7. 14 1. 63 Tuff 16. 36 2. 17 Lithic Tuff 4. 34 1. 01 Andesite 13. 25 1. 86 Travertine 8. 27 1. 14 In this study, it was attempted to propose an experimental relationship between mode I fracture toughness and the tensile strength of the rock. In order to determine the relationship between the tensile strength and the fracture toughness, the tensile strength vs. fracture toughness diagram was plotted in Excel to obtain Eq. 1 and the coefficient of determination (R2) (Figure 1). The coefficient of determination (R2) in Eq. 1 shows that almost 80 percent of the mode I fracture toughness variations can be estimated using the linear relationship (Eq. 1). The relationship is applicable for determining the mode I fracture toughness resulting from the three-point bending test on semicircular specimens containing a straight crack. In the following, the results of this study are compared to those reported by Whittacker (1992) and Zhang (2002). In order to examine the accuracy of the presented relationships, the Root Mean Square Error (RMSE) measure was used which is computed from Eq. 2. In the best case, RMSE is zero. In the relationships, represents the fracture toughness obtained from testing while is the fracture toughness estimated using the relationships. Comparison of the obtained results indicate that the proposed relationship has the capability of precise estimation of the mode I fracture toughness of rocks. Conclusion Given the many difficulties associated with the direct estimation of fracture toughness, indirect estimation methods have been proposed. One of such methods is the estimation of mode I fracture toughness using tensile strength. A linear relationship with a coefficient of determination of 0. 7977 was proposed. The accuracy of this relationship has been verified by comparing its results to those from previous studies.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 598

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 197 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    175-200
Measures: 
  • Citations: 

    0
  • Views: 

    487
  • Downloads: 

    240
Abstract: 

In weak soils with low bearing capacity, the load transfer is done using piles. Therefore, by creating an interposed layer separating the pile from the raft, reactions between raft and pile head will be reduced and the load-bearing role of shallow soil will be more than contact pile situation. Normally, the pile head and shallow soil have a settlement equal to the raft. Thus, the relative settlement of pile and soil in pile head is equal to zero and at the bottom is high and the body friction mobilizes upward. In addition, a portion of load is tolerated by shallow soil and the other portion is tolerated by the pile head, which would be transferred to deeper soil layers. In noncontact state, with the formation of a hard soil layer on which the raft is located, soil mechanical parameters will be improved; while in contact state, the settlement will be decreased by reducing the amount of transferred load to the shallow soil. The transferred load to the shallow soil increases vertical and horizontal stress around piles, so bearing capacity of piles is increased....

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 487

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 240 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    201-224
Measures: 
  • Citations: 

    0
  • Views: 

    583
  • Downloads: 

    326
Keywords: 
Abstract: 

Introduction Soil nails are traditionally designed with uniform length and equal spacing to stabilize slopes which do not meet safety requirements. However, nails with uniform layout in a slope may not be the optimal design if the construction cost is taken into account. The optimal layouts lead to a minimum usage of nails and satisfies the allowable factor of safety and wall deformation. In this study a decreasing trend of nails length along the wall height was considered to investigate the stability and the performance of the wall in different nail patterns. Then nail density was introduced as an important factor on the overall stability and deformation of the wall. It can be beneficial in the preliminary estimation of the required nail length at the beginning of a project. Findings of this study are helpful for effective design of soil– nailed slopes....

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 583

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 326 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Author(s): 

TABARSA ALIREZA

Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    225-246
Measures: 
  • Citations: 

    0
  • Views: 

    917
  • Downloads: 

    352
Abstract: 

Soil has always been a major material in civil projects. Due to progress in science, different studies on the behavior of soil and its engineering characteristics have been conducted. As mentioned, there are different types of soil in nature; a small change in their structure and fabric under different environmental conditions or loading causes high deformation and settlements, which result in a reduction of strength and bonding between soil particles. Also, in this regard, some soft soils exist that are mostly composed of clay particles, with small shear strength and big settlement under low stress. With respect to the above-mentioned characteristics, these soils are referred to as problematic soils. The problematic soils consist of a silicate combination, whose major parts are clay minerals formed under weathering of rocks. Additionally, the precipitation of some soils and ground activity near the surface causes them to become problematic (Beckwith and Hansen [1]). Principally, in engineering, those soils on which construction is not safe, and which are affected...

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 917

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 352 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    247-276
Measures: 
  • Citations: 

    0
  • Views: 

    503
  • Downloads: 

    382
Abstract: 

Construction of highways and high weight structures on compressible soft soils requires planning and sufficient knowledge of geotechnical conditions of the site. Before construction of the desired structure on this type of soils, it is unavoidable to improve and modify these soils to prevent large unpredictable settlements resulting in damages to the structure. “ Preloading” is a method widely used in soil improvement that dates back to 1930s and earlier. It is a simple and economic method of increasing the strength parameters of saturated fine-grained soft soils. Easy implementation, monitoring and measuring the settlement of ground using instrumentation and checking the behavior of...

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 503

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 382 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    277-298
Measures: 
  • Citations: 

    0
  • Views: 

    540
  • Downloads: 

    186
Keywords: 
Abstract: 

Preparation of uniform and repeatable reconstituted sand specimens of required density is a prerequisite for obtaining reliable results from experimental studies. Among different methods of reconstituted specimens, sand pluviation technique is widely adopted by researchers because of its unique advantage. In this study, a new curtain traveling rainer (CTR) is developed for large model sand bed preparation in experimental studies. CTR is a simple and low-cost system which is worked on the principle of air pluviation of sand. It provides specimens with wide range of relative density of sand bed (viz, 30%-90%) and very high degree of spatial uniformity of density distribution while reducing the time of preparation the specimens. A series of laboratory tests is carried out in order to study the performance of the proposed system and the effect of...

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 540

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 186 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Issue Info: 
  • Year: 

    2017
  • Volume: 

    11
  • Issue: 

    2
  • Pages: 

    299-318
Measures: 
  • Citations: 

    0
  • Views: 

    865
  • Downloads: 

    292
Keywords: 
Abstract: 

Bentonite has been used industrially in various construction projects. This material is used, due to its limited hydraulic conductivity, in some cases such as landfill, sealing walls and nuclear waste disposal tanks. Recently, many researchers have investigated the use of bentonite slurry systems for injection into granular soils under static and dynamic loading conditions in order to improve soil engineering performance. In this condition, bentonite slurry is deposited in a loose soil with low pressure and without disturbance in the structure of the soil under injection. Due to the nature of the thixotropy of the bentonite slurry, the injected material is deposited in the form of gel structures in the soil and leads to increasing soil resistance to static and dynamic loads. For suitable soil engineering properties in granular soil, the use of concentrated bentonite slurry is appropriate; high concentrations will limit the penetration of bentonite due to low soil permeability. In order to overcome this limitation, slurry rheological properties such as viscosity must be corrected in order to increase the depth of sand penetration. Other researchers observed that with the reduction of viscosity in the cement slurry with micro-size particles, the amount of its penetration in the sand column significantly increased....

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 865

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 292 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0