اکبر چشمی

The present study has investigated the effect of vinyl acrylic polymer emulsion (VA) on the shear strength of aeolian sands in the Khuzestan plain. For this purpose, after sampling the aeolian sands of the mentioned area, a standard compaction test was performed and the optimum water content and maximum dry density of the aeolian sand were determined. Then, solutions with percentages of 10, 20 and 30% of polymer material were made and added to the aeolian sand in such a way that it reached the optimum water content. The prepared soil with maximum dry density was placed in square metal molds kept in the laboratory for 1, 7, 14 and 21 days and then subjected to direct shear test. The results of the direct shear test on the stabilized samples showed that by increasing the curing time and the concentration of the polymer solution, cohesion and the shear strength increase and the angle of internal friction decreases. So the polymer solution with a concentration of 30% has caused a 146% increase in shear strength aeolian sand. Electron microscope images (SEM) show the creation of bridges between sand grains in the stabilized samples, which is the reason for the increased cohesion and shear strength of the samples.

 One of the subjects of geotechnical engineering is soil bearing capacity, which is a function of the engineering properties of subsurface deposits and foundation characteristics. In this study, the results of 78 exploratory boreholes drilled in Mahshahr Special Economic Zone and Bandar-e-Imam were used to produce engineering geological maps with the aim of determining the soil bearing capacity in that area. The result from the boreholes shows that the sediment of the area is mainly clay and to a lesser extent silty clay and silty sand. After determining the soil classification, engineering parameters were determined based on laboratory test results. Then by using Hansen's formula and considering the allowable settlement of the foundation, bearing capacity was calculated for square foundation (1×1) and (2×2) meters, strip foundation with buried unit depth and a mat foundation (10×20) meters with buried depth one and two meters. By using the ArcGIS software, the load capacity map of the study area was produced and result shows that the allowable bearing capacity in this area varies between 0.40 to 0.98 (kg /cm2) and the northern area has higher load capacity than other area.

The engineering properties of geomaterials are determined by laboratory and In-situ testing. Problems associated with sampling, especially in coarse-grained soils, limit the laboratory testing applications to determine the engineering properties of these types of soils. Engineering geological studies would help in-situ test selection as well as managing of the coast and the validity of test results. To increase the height of the Gotvand regulatory dam, determining deformation modules of subsurface material is needed, so a multistage method has been suggested and done. For this purpose, a multi-step method was proposed and performed. In the first stage, the engineering geological properties of subsurface materials have been investigated by using geological study and exploration borehole data. The subsurface materials are gravel with some sand, silt, and clay. At this stage, to determine the modulus of deformability, pressuremeter (PMT), downhole and crosshole tests were performed. Due to the coarse texture and, heterogeneity of the materials, good results were not obtained from the pressurmeter test. in the second stage and with reference to data in first stage, the extension of same strata beneath the dam has specified in river’s left bank and the measurement of deformation modules has done by plate loading test (PLT) using circular plates of 60 cm diameter. In the last stage, to investigate the effect of plate dimensions and particle size, PLT using circular plates of 120 cm diameter has been done. By changing the loading plate diameter from 60 to 120 cm, the average measured modulus decreases from 2868 to 1075 kg/cm2. In this paper, while expressing the importance of engineering geology studies in selecting suitable in situ tests, the results obtained from various tests have been reviewed.

Description and Understanding the sedimentary environment helps a lot in the initial estimation of the engineering properties of materials and planning of geotechnical studies. Most of the quaternary sediments (coarse and fine grained) of the Isfahan city were deposited by the Zayandehrood river. Understanding the geotechnical characteristics and subsurface development of these sediments are essential in the old sedimentary environment for a couple of reasons. Firstly, it is difficult to determine the geotechnical characteristics of coarse-grained sediments and there is uncertainty in the subsurface development of these sediments at distant locations from the Zayandehrood river. Secondly, it is development of construction and the necessity of digging underground spaces Therefore, in this study, using the geotechnical data of 384 boreholes, maps of the approximate range of coarse-grained sediments of the Zayandehrood River were prepared at depths of 5, 10, 20 and 30 m and their geotechnical characteristics were statistical analyzed by the results of laboratory and in situ tests. The results show that the geotechnical characteristics of coarse-grained sediments do not change significantly with the change of depth and the approximate range of subsurface expansion of this river has been in the past in places other than the present river route.

Investigation of the effect of temperature on soil strength is one of the issues which has been considered by many researchers in recent decades. In this study to investigate the effect of temperature on the undrained shear strength (Cu) of clay soils, a cell with the capability of both changing and keeping fixed the temperature of sample, was designed and constructed. After determining the index properties of samples for Kaolinite clay soil, undrained shear strength (Cu) test was carried out on saturated clay soil at 10, 20, 30, 40, 50, 60 and 70 ° C. Repeatability of the results was confirmed by repeating tests on samples with the same properties a given temperature. The results showed that by increasing the temperature, the Cu values decreased so that, as the temperature raised from 10 ° C to 70 ° C, the values Cu were reduced from 26.6 to 10.94 kPa. Accordingly, in the studied temperature range, an empirical relationship between temperature and Cu (with R2= 0.96) was proposed. The general shape of the stress–strain curves of the samples in different temperature was the same and in strain level of 20% was linear. Increasing the temperature caused to decline in the range of elastic deformation and enhancement in the range of plastic deformation of the samples; in addition, by increasing the temperature, the angle of the failure plane was decreased. The measurement of axial expansion stress (AES) indicated enhancement of the stress by increasing the temperature.

The increasing amount of demolition and construction waste (D&CW) materials has created many problems in large cities. Recycling waste materials helps to protect the environment. D&CW can be used in many projects, especially in road construction, retaining walls, landscaping and pavements. In this research, a project in which, D&CW used as fill materials to stabilize a deep excavation is investigated. The project site is located at the southwest of Tehran and the west of the Kan River. Site soil is basically composed of the C alluvium of Tehran. Strength parameters of soil were determined using recursive stability analysis. By performing an experimental embankment of D&CW (500 m length, 8 m width and 0.5 m height) and compacting it, in-situ density, plate load and dynamic probing tests were implemented and parameters of D&CW were obtained. Then stability analysis of excavation was performed under different conditions using Geo-Slope and the results showed that the D&CW embankment is capable to provide factor of safety. Finally, in order to control the quality of execution, according to the field observations, the guidelines were suggested to use D&CW. The results of this study show that D&CW can be significantly usable in engineering applications.

When the metal is in contact with the soil, there is the possibility of sticking soil to the metal surface. For determining the tension stress for soil separating from metal surface the cone pullout device designed. In this apparatus, a cone penetrates into the soil, stopping it for a specific time and, then, separating from the soil. In the present research, according to previous studies and ideas about this subject, cone pullout test device is designed and manufactured. By performing 90 tests on a montmorillonite clay soil with different values for stope time and separation speed, the effect of these variables was studied. The results showed optimum stope time (t =5 min), and separation speed cone (15 mm /min) was determined. To evaluate the reproducibility of the results, by performing other 60 tests on two other kaolinite clay soils, coefficient of variation (14.49\geqCv\geq1.4) and accuracy index (1.22\geqP\geq1.01) were determined. these values showed which results were reputable and acceptable. Because of the effect of moisture content on the engineering properties of fine-grained soil, the effect of moisture changes on tensile stress for separation of metal from soil was studied. The results of the study showed that with an increase in water content, the tension stress decreased. Accordingly, linear relationships were proposed between soil moisture content and tensile stress for montmorillonite and kaolinite clay soils. Slope of the curve moisture content versus tension stress for montmorillonite clay soil and kaolinite clay soil are 1.25 and 0.82 respectively. Therefore, it can be concluded that the slope of the curve corresponds to the soil type; increasing plastic index increases tension stress.

Different methods have been introduced for estimating the performance of tunneling boring machines (TBMs) for each area; therefore, their use in other projects may lead to errors in different geological conditions. Therefore, it is necessary for each project to use models that have similar geological conditions with the project. In this paper, using the actual machine data in the Zagros Water conveyance Tunneling Project, the machine's performance has been predicted by conventional models. Then, the results obtained from the common models including the empirical models of NTNU, Palmestrom (1995) and the theoretical model of CSM compared with the results obtained from Hassnpour et al. (2009, 2011) model, which has been developed based on data from projects with similar geological conditions, and the differences between them are quantitatively explained. The results of this study indicate that the empirical model of Hassanpour et al., due to the compatibility of the database with internal projects, shows the results closer to reality than the other models. Then, empirical models of NTNU and RMi provide more reliable results than CSM model due to consideration of different geological parameters, especially rock masses.

The proposed classification based on the combination of geological variables and geotechnical parameters provides the possibility of using geological knowledge in estimating the geotechnical parameters. The city of Tehran is one of the metropolises that founded on Quaternary alluvium. The alluvium is divided into four groups, A, B, C, and D, based on age and formation conditions. Some researchers have proposed a new classification using the combination of geological variables and geotechnical parameters for A and C Tehran's alluvia. The aim of this study is to sub-classification of unit B of Tehran alluvia based on combination of geological variables and geotechnical parameters. In this research, based on geological findings in 66 locations of Tehran's alluvia, the geological variables affecting the geotechnical parameters of the coarse-grained B alluvia including grain size, grain form, grain contact, cement between grain, homogeneity and layering were identified and based on these variables, unit B was divided into four units of Bn1, Bn2, Bn3 and Bn4. Using the results of 27 performed direct shear test and 70 plate loading tests in specified units, the geotechnical parameters of these four units, including the internal friction angle, cohesion, and modulus of deformability were determined. With combination of geological variables and geotechnical parameters, new classification of unite B was proposed that make it is possible to estimate the geotechnical parameters based on the geological variables for this alluvium.

Soil classification is one of the major parts of geotechnical studies. So assessment of existing methods for soil classification in different areas is important. For soil classification is used in situ and laboratory test results. Sampling and identification tests are laboratory methods for soil classification. CPTu test is in situ method for soil identification and classification, due to accuracy and speed, this test is used widely in geotechnical study today. Many researchers are proposed some charts for soil classifications based on the parameters measured in CPTu test. In this paper for evaluation the performance of these methods, 58 CPTu test results have been used. These tests are related to four areas in southern Iran. The soils are classified by CPTu methods and then they are compared with 372 laboratory soil classification. Research results show the chart proposed by Robertson (1990) which based on Qt, Ft and Bq variables has the best adaptation with the laboratory soil classification in these studied areas. Then according to data obtained from research, proposed a modified charts based on Rf, qt-u0/σ΄ v , that show 90% adaptation with laboratory soil classification.

Coefficient of consolidation (CV) is one of the important parameters used in geotechnical design. This parameter is usually achieved from one dimensional consolidation test in laboratory. Cone penetration Test (CPT) is an in situ test, in this test can be measure pore water pressure with time this test has previously been introducing dissipation test. Teh (1987), Houlsby and Teh (1988), Teh and Houlsby (1991) and Jones and Rust (1995) have been proposed different methods to determine CV from CPTu results. In this paper, have been used 43 dissipation tests and 35 one dimension laboratory consolidation tests that were conducted in three areas in southern Iran and are compared CV are obtained from CPTu test by from 4 methods listed above with each other’s and one dimensional laboratory consolidation test. The results show that CV obtained from laboratory test is higher than the value obtained by from Teh & Houlsby (1991) method and lower than the value obtained from others methods. The similarity of results obtained from laboratory test in terms of amount and trend are closer to results obtained from Teh & Houlsby (1991) method. The empirical relationships between laboratory and in situ CV are proposed. For all equations, coefficient of correlation is higher than 0.7. The highest value is belong to Houlsby & Teh (1988) method and the least value is belong to the Jones & Rust (1995) method.
Once the empirical equation is proposed for each site indecently, coefficient of correlation in all methods is high but while the empirical equation is proposed for all sites together coefficient of correlation is decrease. Thus these empirical equations are influenced by the characteristics of each area so for each area must be independently evaluated and empirical equation are proposed.

Clogging occurs during mechanical tunneling with a Tunnel Boring Machine (TBM) because of adhesion of clayey soils to the cutter head and conveyor system. The present study examined the effects of water and sand contents on clogging in Montmorillonite clayey soil. Testing was carried out using an adhesion test device on 28 samples with different water and sand contents to determine adhesion stress and degree of clogging. The results indicate that the consistency index (Ic) of the samples decreases as the sand and water content increases. The results for variation of adhesion stress versus water content at different sand contents formed similar bellshaped curves. In all graphs، an increase in sand content decreased adhesion stress. Adhesion stress increased until the water content increased to 138%، at which point it began to decrease. The results show that adhesion of the soil to the surface of the metal piston did not occur in samples having a sand content of >40% and in samples with >133% water content having a sand content of <40%، Ic>0. 5 adhesion occurred.

Measuring of uniaxial compressive strength (UCS) of intact rocks is necessary in many engineering projects. In deep well drilling for petroleum production or exploration drilling in deep tunnels، because depth wells، obtain suitable core samples for UCS test is too extensive and sometimes impossible. Therefore indirect method for UCS determine (for example using rock particles) is common. One of these methods is known as indentation test. In this test an indenter that is hard penetrate in to rock particle which surrounded by resin is used. In this paper، 11 microcrystalline limestone block samples from carbonate Zagros formation outcrops is prepared and UCS test in laboratory is performed. Then cores are crushed and 720 rock particle samples with 2، 3 and 4 millimeters size is prepared. Indentation test with indenter 0. 6، 0. 8 and 1 millimeters diameter is done and critical transitional force (CTF) for each particles is determined. Empirical equation between UCS and CFT for different samples and indenter with R2≥0. 78 is suggested. Using multiple regression general equation between UCS، CFT، particle size (D) indenter diameter (I) with R2=0. 85 is proposed. Verification of the proposed equations with 135 indentation tests on 3 microcrystalline limestone samples and comparing measuring UCS in laboratory with estimate UCS are evaluated. This comparison showed that 88% they are similar.

One of the major issues in dam construction is water seepage، post impounding. Assessment and prediction of the amount of water leakage can be useful in preventing such events. The Seymareh dam has been constructed on the Seymareh River in Ilam province، Southwest of Iran. The dam controls the floods and generates hydroelectric power. It is already under impoundment and the seepage problem is being considered. Grout curtains have been employed in two directions at the right abutment of the dam to control the seepage. The normal reservoir level is 720 m and it has been impounded at the 660 m level up to the point. The purpose of this study is to predict the amount of water seepage through the right abutment of the dam by using numerical modeling. For this purpose، a new GW finite element code was used for a two-dimensional simulation of the water seepage. The Levels of the observations wells and the discharges of the downstream springs on the right river bank are used as the main data for this modeling and its verification. Assessments show that if the dam impoundment rises to the normal level، significant seepage may occur through the right abutment.

The adhesion of clay minerals to metal surfaces leads to clogging of equipment during mechanized tunneling through clay-bearing formations. Among proposed methods to measure adhesion and evaluate clogging potential, Piston Separation Device is found practical and capable to be developed. The Device was designed based on literature and built in this study. Performance of test device was investigated by natural and synthetic materials (water, honey, stick and clayey soil). Statistical study confirmed accuracy and reproducibility of test results. Study of wetness effect in adhesion of Montmorillonite showed adhesion increases with decrease in moisture to twice as much Plasticity Limit (=2PL). Also it is perceived that clogging will occur in wetness much than twice as much Plasticity Limit but in less not.

One of the methods for evaluation mechanical characteristics of intact rock is studying on rock single particle strength. In these paper, single particles loading apparatus was introduced then design stage and component this apparatus was described. Repeatability test results from static and penetration test on homogeny particles were investigated and behavior charts this samples were drawn. Samples photographs before and after tests were taken and particles fracture mechanism were described. For investigation repeatability test results, collective behavior graphs were drawn and were compared to each other and validation degree of results by using small sampling theory were evaluated. For evaluation the performance apparatus and results in estimating the UCS, 480 single particle loading (SCSI) of micro-crystalline limestone determined and compared with UCS, then presented relationship between them with correlation of coefficient larger than 0.83. This subject shows the ability apparatus in UCS indirect prediction.

Determination of uniaxial compressive strength (UCS) of intact rock is an important mechanical parameter required for many engineering projects. In some engineering projects for example well drilling for production petroleum because of more deep well exist limitation for obtain rock core sample and determination UCS. On the other hand determination this parameter is essential in order to analysis well wall stability and wells development program. Because of this, the idea of using drilling cuttings is proposed for determination UCS. In this paper in order to develop relationship between UCS and single compressive strength (SCS) were used from 7 block sample microcrystalline limestone from Asmari formation outcrops. Then UCS test was performed and was determined uniaxial compressive strength. Next these samples were crushed and were prepared 420 single particles. Then SCS for each particle is determined. Since shape of particles effect on particle strength therefore shape of particles has been modified and total particles that used for determination SCS was spherical. In order to study effect size of particle, particles with diameters 2, 3 and 4 millimeter is prepared and determined SCS for each particles. With increase diameter of particle, increase SCS. In order to eliminate effect of size particles is defined variable size and strength and is proposed chart between them. Coefficient of correlation between SCS and UCS is more than 0.91 that present exist good correlation between them.

Determination of geotechnical parameter in coarse grained alluvia is important subject in geotechnical study. The paper presented a method that can be used to determine the angle of friction with use from particle shape for coarse grained alluvia. In this paper from 9 location in Tehran alluvia prepared soil samples. The angle of friction was determined based on the results of a number of laboratory test (Classification, triaxial and direct shear tests). Then, images of the grains forming the samples were taken and compared with the chart presented by Krumbein and Sloss (1963). In this manner determined shape grains variable (Sphericity and Roundness). In order to 2520 grains were taken images with use by microscope and without microscope. A relationship between the angles of friction was determined with laboratory tests and shape grains variable is investigated and proposed. With increase of angularity and decrease roundness, angles of friction increases.

City of Tehran is founded on Quaternary alluvium. During the last years, several researchers have studied characteristics of this alluvium. Amongst them, Rieben classification has been the most widely used classification rather than others. Rieben (1955) divided Tehran alluvium to four categories, A, B, C and D which are ranged from old to young, respectively, in terms of geologic age. In Rieben study, age and general characteristics of alluviums are considered rather than geotechnical and engineering applications. Study of alluvium based on age can give useful information about history of basin sedimentation and relevant change's trends and even it may help geotechnical engineers for preparing study plan and making sound conclusions over undertaken studies. For doing so, it is required to evaluate alluvium classifications with respect to sedimentation types. In order to evaluate Rieben classification capabilities for geotechnical studies of Tehran alluvium, following subjects are studied in this research: (A) Description of Rieben and other classifications that are presented based on age and specification of geology. (B) Discussing advantages and disadvantages of existing classifications in geotechnical studies. (C) Analysis of Tehran geological maps with consideration of alluvium formation and making comparison of these maps with some boreholes, test pits and site visit results. (D) Discussing geological factors affecting on geotechnical specifications of Tehran alluvium.