Soil Mechanics Lab. (LCIV 3151) Experiment No.3: Grain size analysis Part I: Sieve Analysis. Part II: Hydrometer analysis.

Transcription

1 Soil Mechanics Lab. (LCIV 3151) Experiment No.3: Grain size analysis Part I: Sieve Analysis. Part II: Hydrometer analysis. 1. Purpose: This test is performed to determine the percentage of different grain sizes contained within a soil. The mechanical or sieve analysis is performed to determine the distribution of the coarser, larger-sized particles, and the hydrometer method is used to determine the distribution of the finer particles. 2. Significance: The distribution of different grain sizes affects the engineering properties of soil. Grain size analysis provides the grain size distribution, and it is required in classifying the soil. Part I: Sieve Analysis: 3. Apparatus: 1- Sensitive balance. 2- Hot plate. 3- Set of sieves (No.4 (4.75mm) No.200 (0.075mm)). 4. Procedures: حضر ع ح ي انررتح و جففها و س ها جافح ن عرف وز انع ح انجافح انكه m. t غسم انع ح عه ي خم رقى 200 و ج ع انغثار وان اء ان ار ي ان خم ف وعاء و سر ر تانغسم حر ظهر قاء ان اء ان ار ي ان خم فركى انع ح قذ خهد ي انغثار و كى ذخهص ا ي ذالصق حث ثاخ انررتح. قىو ترجف ف انع ح تىاسطح قرص انرسخ و ضع انع ح ف ان اخم ان رذثح ي ي خم فرحح 4.75mm وحر ي خم 0.075mm و ثذأ تر خ م انع ح. سجم انىز ان رراكى ان رثق نكم ي خم و جر انحساتاخ انخاصح تانرجرتح Calculations: 1. Compute the percentage by the weight of various grain sizes, computing this on the basis of the weight of the entire sample. 2. Calculate the cumulative percentages of material passing each of the sieves. 3. Plot the grain size curve on semi-log paper 1

2 Sieve opening (mm) 4775 Mass of cum. Ret. (g) M1 % cum. Ret. M % 1 M t *100 %Passing 100-% cum. Ret Pan M2 M3 M4 M5 Mt %Gravel = %passing 76.2mm - %passing 4.75mm. %Sand = %passing %passing 0.075mm. % fine= % Gravel - % Sand. 4. Compute Coefficient of gradation and Uniformity coefficient. C z C u 2 D30 D D D D C z : Coefficient of gradation. C u : Uniformity coefficient. D10 D30 D60 : The corresponding diameter for 10% passing. : The corresponding diameter for 30% passing. : The corresponding diameter for 60% passing. Part II: Hydrometer Analysis: 3. Apparatus: 1- Sensitive balance. 2- Hydrometer. 3- Control cylinder. 4- Sedimentation cylinder. 5- Thermometer. 6- Mixer. 7- Stop watch. 2

3 4. Procedures: - 1 قىو ترجف ف انع ح ان ارج ي ي خم رقى 200 و أخذ ي ها 50grams تعذ انرجف ف. - 2 أل كىت ت قذار 125 ml ي ان اء يع إضافح عايم حفاز ن ع م عه ا رشار حث ثاخ انررتح. 5grams ت سثح %4 أ يا عادل Sodium hexametaphosphate - 3 أل اسطىا ح انضثظ Cylinder( )Control ت حرىي أحذ انكىت ثى ك م االسطىا ح تان اء حر عاليرها انعه ا أ ت ا أل.1000ml - 4 ذخم ان Hydrometer ف Control Cylinder و رظر قه ال حر سرقر و سجم قراءذه وانر س ها.Zero Correction - 5 ضع انررتح ف انكىب ا خر و قم انررتح انضحهح )Slurry( إن خالط ن ذج 5 دقائق تح ث ض ف ياء نهخالط كه ا احرج ا تح ث أل صف انخالط تان اء. - 6 قم خه ظ انررتح إن اسطىا ح انررس ة Sedimentation Cylinder و ض ف ياء حر عاليح االسطىا ح أ.1000ml - 7 غهق فىهح االسطىا ح و ع م عه ذقه ثها 30 يرج خالل دق قح واحذج و رظر قه ال ثى ذخم ي سا انحرارج و ان Hydrometer ف اسطىا ح انررس ة. - 8 سجم ق ح انحرارج وقراءج انه ذروي رر تعذ ) 1 دق قح ( حر ذصثح قراءج انه ذروي رر يساو ح إن.Zero correction 5. Calculations: 1- Calculate the equivalent particle diameter (D): L( cm) D k T (min) k : Factor depend on G s and temperature Given from table1. L : Distance between water surface and center of gravity of hydrometer bulb. This distance is related to hydrometer reading and given from table 2. T : Elapsed time (Cumulative). قثم انحصىل عه ق حL ي انجذول عه ا ذصح ح ق ح قراءج انه ذروي رر ت ا ر اسة يع انرىذر انسطح و انر ذكى غانثا تإضافح وحذج نقراءج انه ذروي رر )+1 ) R R 1 corrected min scus actual F m 3

4 2- Calculate the corrected hydrometer reading (Rc): R C R actual Zero Correction C C T : Correction factor for temperature, given from table Calculate the percent finer (%P): Rc a % P W S a: Correction factor given from table 4. W S : Total weight of soil sample =50grams. T 4- Calculate the adjusted percent finer as follow: P F P 200 A 100 F 200 : % Passing sieve No.200 Now, after finding D and P you can complete the grain size curve of sieve analysis exp. A (D (opening diameter for sieve analysis and equivalent particle diameter for hydrometer analysis) on the x-axis versus (% passing for sieve analysis and P for hydrometer analysis) on the y-axis. A 4

5 Date Hydrometer Test Data Mass of soil sample (Ms) 50 grams Specific gravity of soil solids 2.65 Dispersing Agent Sodium Hexametaphosphate Zero correction +9 Meniscus Correction +1 Time Elapsed Time (min) Temp ( C) 05/03/2011 4:22 pm /03/2011 4:23 pm /03/2011 4:24 pm /03/2011 4:26 pm /03/2011 4:30 pm /03/2011 4:38 pm /03/2011 4:52 pm /03/2011 5:22 pm /03/2011 6:52 pm /03/2011 4:22 pm /03/2011 4:22 am Ra 5

6 Table 1: Variation of K with G s Table 2: Variation of L with hydrometer reading 6

7 Table 3: Temperature correction factor. Table 4: Correction factor a for unit weight of solids. 7