SOIL MECHANICS Assignment #2: Soil Classification Solution.

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Clare Walsh
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Geotechnical Engineering Research Laboratory One University Avenue Lowell, Massachusetts 01854 Edward L. Hajduk, D.

1 Geotechnical Engineering Research Laboratory One University Avenue Lowell, Massachusetts Edward L. Hajduk, D.Eng, PE Lecturer PA105D Tel: (978) Fax: (978) e mail: Edward_Hajduk@uml.edu web site: DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING PROBLEM #1 (60 Points): GIVEN: SOIL MECHANICS Assignment #2: Soil Classification Solution. Table 1. Soil Index Testing Summary. Sample D422 D4318 Sieve Number % Retained LL PL Pan Pan Pan 9.8 NA NA REQUIRED: Determine USCS and AASHTO soil classifications for each soil sample Assignment 2 Solution Page 1 of 10

2 SOLUTION: USCS Classification: Plot grain size distribution for all soils and determine D 60, D 30, and D 10 when necessary for Soil Samples #1, #2, and #3. Figure A. Grain Size Distributions and D 60, D 30, and D 10 for Samples #1, #2, and #3. Calculate C c and Cu using information in Figure A for Samples #1 and #3 and the equations shown below. See Table A for summary of C u and C c calculations. Coefficient of Uniformity = C u = D 60 D 10 Coefficient of Curvature (a.k.a. Gradation) = C c = (D 30 ) 2 (D 60 xd 10 ) Assignment 2 Solution Page 2 of 10

3 Table A. Summary of C u and C c calculations. Parameter Sample #1 Sample #3 D 60 (mm) D 30 (mm) D 10 (mm) C c C u Knowing that PI = LL-PL, LL vs. PI was plotted for Samples #2 and #3 on Figure B. Figure B. Atterberg Limits Test Results Plotted on Casagrande s Chart. Since each soil sample has a % Passing a #200 sieve < 50%, use Figure 3 of ASTM D2487 to classify soil. See Figures C thru E for soil classification using ASTM D2487 Figure 3 for Soil Samples #1 thru 3, respectively Assignment 2 Solution Page 3 of 10

4 No Gravel FC = 3% C u = 1.23 SP - Poorly Graded Sand Figure C. USCS Soil Classification of Sample #1 (using Figure 3 of ASTM D2487). No Gravel FC = 18% SC-SM- Silty, Clayey Sand Figure D. USCS Soil Classification of Sample #2 (using Figure 3 of ASTM D2487) Assignment 2 Solution Page 4 of 10

5 No Gravel FC = 10% C u = 1.37 MH SP-SM - Poorly Graded Sand with Silt Figure E. USCS Soil Classification of Sample #3 (using Figure 3 of ASTM D2487). AASHTO Classification: Use Table 2 from ASTM D3282. Determine % Passing #10, #40, and #200 sieves (see Figure A for grain size distribution plots). See Figure F for soil classification using ASTM D3282 Table 2 for Samples #1 thru 3. General Classification Group classification TABLE 2 Classification of Soils and Soil-Aggregate Mixtures Granular Materials Sample (35 % or less #1passing No. 200 (75 µm)) A-1 A-2 Sample #3 A-3 A-4 A-5 A-6 A-1-a A-1-b A-2-4 A-2-5 A-2-6 A-2-7 Silt-Clay Materials (More than 35 % passing No. 200 (75 µm)) Sieve analysis, % passing: No. 10 (2.00 mm) 50 max No. 40 (425 µm) 30 max 50 max 51 min No. 200 (75 µm) 15 max 25 max 10 max 35 max 35 max 35 max 35 max 36 min 36 min 36 min 36 min Characteristics of fraction passing No. 40 (425 µm): Liquid limit Plasticity index... 6max... N.P. 40 max 10 max 41 min 10 max 40 max 11 min 41 min 11 min 40 max 10 max 41 min 10 max 40 max 11 min 41 min 11 min A Usual types of significant constituent materials Stone Fragments, Gravel and Sand Fine Sand Sample #2 A-7 A-7-5, A-7-6 Silty or Clayey Gravel and Sand Silty Soils Clayey Soils General rating as subgrade Excellent to Good Fair to Poor A Plasticity index of A-7-5 subgroup is equal to or less than LL minus 30. Plasticity index of A-7-6 subgroup is greater than LL minus 30 (see Fig. 1). Reprinted with permission of American Association of State Highway and Transportation Officials. Figure F. AASHTO Soil Classification of Sample #1, #2, and #3 (using Table 2 of ASTM D3282) Assignment 2 Solution Page 5 of 10

6 Problem #1 Summary: Sample Soil Classification USCS Group Symbol & Name AASHTO #1 (SP) Poorly Graded Sand A-3 #2 (SC-SM) Silty, Clayey Sand A-2-4 #3 (SP-SM) Poorly Graded Sand with Silt A-2-7 PROBLEM #2 (40 Points): GIVEN: Soil #2 Soil #3 Soil #1 Figure 1. Mechanical Sieve and Hydrometer Results for Problem #2. Table 3. Atterberg Limits (ASTM D4318) for Problem #2. Soil LL PL # #2 NA NA # Assignment 2 Solution Page 6 of 10

7 REQUIRED: Classify the soils in accordance with the Unified Soil Classification System (USCS) and AASHTO. USCS Classification: Calculate % Gravel, % Sand, and % Fines from Figure 1. A summary of these percentages is provided in Table B. Table B. Summary of % Gravel, % Sand, and % Fines from Figure 1. Soil % Gravel % Sand % Fines Soil Fine Grained Coarse Grained Fine Grained Knowing that PI = LL-PL, PI vs. LL was plotted for Soils #1 and #2 on Figure G. Figure G. Atterberg Limits Test Results Plotted on Casagrande s Chart. Therefore, use Figure 1 from ASTM D2487 for Soils #1 and #3 and Figure 3 from ASTM D2487 for Soil #2 to classify the soils. See Figures H thru J for soil classification using ASTM D2487 Figures for Soils #1 thru #3, respectively Assignment 2 Solution Page 7 of 10

8 0% Plus #200 CH Fat Clay LL = 61 Figure H. USCS Soil Classification of Soil #1 (using Figure 1 of ASTM D2487). For Soil #2 (Using Figure 3, ASTM D2487): C c (D (D 60 ) D ;C ) u D D Soil D 10 (mm) D 30 (mm) D 60 (mm) # C c C u Assignment 2 Solution Page 8 of 10

9 2% Gravel FC = 0% C u = 2.7, C c = 1.1 SP Poorly Graded Sand Figure J. USCS Soil Classification of Sample #2 (using Figure 3 of ASTM D2487). 50% Plus #200 CL Sandy Lean Clay LL = 39 Figure I. USCS Soil Classification of Soil #3 (using Figure 1 of ASTM D2487) Assignment 2 Solution Page 9 of 10

10 AASHTO Classification: Use Table 2 from ASTM D3282. Determine % Passing #10, #40, and #200 sieves (see Figure 1 for grain size distribution plots). See Figure K for soil classification using ASTM D3282 Table 2 for Soils #1 thru 3. Soil #1 Soil #2 Soil #3 Figure K. AASHTO Soil Classification of Soils #1, #2, and #3 (using Table 2 of ASTM D3282). Problem #2 Summary: Sample Soil Classification USCS Group Symbol & Name #1 (CH) Fat Clay AASHTO A-7 (Acceptable) A-7-5 #2 (SP) Poorly Graded Sand A-1-b #3 (CL) Sandy Lean Clay A-6 EXTRA CREDIT (+5 Points): Which discipline of civil engineering you would like to work in when you graduate? Write a paragraph or two why you have selected this discipline. Use Guest Lecture assignment guidelines. Self-explanatory Assignment 2 Solution Page 10 of 10

SOIL CLASSIFICATION BASICS Commonly based on grain size and soil consistency. Several classification systems exist:

SOIL CLASSIFICATION BASICS Commonly based on grain size and soil consistency. Several classification systems exist: 1. Unified System (USCS) (ASTM D2487-11). 2. American Association of State Highway and