Geotechnical Engineering 2 Lecture Correspondence PDF

MODULE IN GEOTECHNICAL ENGINEERING 2...

MODULE IN GEOTECHNICAL ENGINEERING 2 CE 422 CIVIL AND GEODETIC ENGINEERING DEPARTMENT SCHOOL OF ENGINEERING AND ARCHITECTURE Propertyofofand Property andfor forthe theexclusive exclusiveuse useofofSLU. SLU.Reproduction, Reproduction,storing storingininaaretrieval retrievalsystem, system,distributing, distributing,uploading uploadingororposting postingonline, online,orortransmitting transmittingininany anyform formororby byany any i means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited. prohibited.  CE 422 COURSE LEARNING OUTCOMES At the end of the module, you should be able to: 1. Calculate the stresses transferred to underlying soils applied by the super structural loads 2. Apply the different methods to estimate compressibility and settlement of soils for shallow foundations. 3. Demonstrate proficiency in conducting the different methods and procedures in the determination of soil shear strength and how to interpret GEOTECHNICAL these data necessary for solving other related problems to civil ENGINEERING 2 engineering. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any ii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  “Successful and unsuccessful people do not vary greatly in their abilities. They vary in their desires to reach their potential” – John Maxwell COURSE GUIDE COURSE OVERVIEW In this course, you will learn about soil as part of the design parameters. This course will enable you to identify and determine the stresses through different loading conditions, settlement, and shear strength of soil. As a result of your educational experiences in the course CE 422, you should be able to: 1. Calculate the stresses transferred to underlying soils applied by the super structural loads 2. Apply the different methods to estimate compressibility and settlement of soils for shallow foundations. 3. Demonstrate proficiency in conducting the different methods and procedures in the determination of soil shear strength and how to interpret these data necessary for solving other related problems to civil engineering. Your academic experience as a Civil Engineering student will be utilized in this course. To ensure that you will demonstrate the above cited course learning outcomes at the end of the semester, this module is divided into the following: MODULE 1: In Situ Stresses – This aims to give you an overview of the components of stress determination through different condition of soil strata. This module includes the concept of effective stress, stresses in saturated soil with different seepage conditions, seepage force, conditions for heaving, use of filters, and capillary rise in soils. MODULE 2: Normal and Shear Stresses on a Plane – This aims to give you an overview of the stresses on a plane. It will enable you to determine the normal and shear stresses on an inclined plane with known stresses on a two-dimensional stress element. This module includes the use of derived equation, Mohr’s Circle, and Pole-Method. MODULE 3: Stresses in a Soil Mass – This aims to give you an overview of the increase in the soil stress. It will enable you to analyze and determine the net increase due to different loading conditions. This module includes the determination of increase in vertical stress at a certain depth due to the application of load on the surface, the loading type includes: point load, line load, uniformly distributed load, linearly increasing vertical loading, embankment loading, uniformly loaded circular and rectangular area. MODULE 4: Compressibility of Soil – This aims to give you an overview of the fundamentals of settlement. It will enable you to analyze and compute the compression of soil under foundations or other loading conditions. This module includes the different broad categories: Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any iii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  elastic settlement, primary consolidation settlement, and secondary consolidation settlement. MODULE 5: Shear Strength of Soil – This aims to give you an overview of the parameters used to analyze soil stability problems. This module includes the different methods to estimate the shear strength parameters of the soil. Review the course study guide and study schedule for your guidance. COURSE STUDY GUIDE Finishing this course successfully relies heavily on your self-discipline and time management skills. The course modules were prepared for you to learn diligently, intelligently, and independently. Keeping yourself motivated to follow the schedules specified in the learning plan, maintaining excellence in the expected student outputs, and mastering the different technologies and procedures required in the delivery and feedback for this course, will instill in you important qualities you will need in the future as a civil engineer practicing your profession. The following course guides and house rules are designed for you to practice decorum consistent with standards expected within a formal academic environment. These guides shall lay the groundwork for consistency, coherence, cooperation, and clear communication among learners and instructors throughout the conduct of this course: 1. MANAGE YOUR MINUTES. Create a study routine and stick to it. Keep requirement deadlines and study schedules always in mind by providing visual cues posted in your place of study or listed in your reminders (electronically, online, or on paper). Remember that there are other daily activities that take up your time, not to mention other courses you may be concurrently taking. Choose a time of day when you are most likely to maximize learning. Communicate your schedule to other members of your household so they could help you keep it. It would also help to prepare a dedicated space in your residence conducive for learning. 2. MIND YOUR MANNERS. Treat the distance learning environment as an academic space not too different from a physical classroom. Do not do in the distance learning environment, acts you would not normally do in a face-to- face classroom set up. Avoid asking questions that have already been answered in the lessons or in the instructions previously discussed or provided. Acts like these will reflect your poor focus and uninspired preparation for this course. Practice Electronic Conversation Etiquette in group chats, open forums, and similar electronic venues. a. Use appropriate language and tone, correct grammar and spelling, and complete sentences acceptable in an academic forum. Avoid Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any iv means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  text-speak, slang, all caps, and other informal expressions in your posts. b. Express your opinions politely and do not dominate the conversation. c. Avoid lengthy as well as offensive posts by sticking to the topic of the discussion. d. Take time to understand the salient points of the discussion, and provide a meaningful and well-thought response to the posts of other participants. e. For a live meeting or video/voice conferencing set-up, mute your microphone when you are not speaking to keep the focus on the main speaker. 3. MASTER THE MEDIUM. The distance learning courses will be delivered making use of the institutional Google Suite account of Saint Louis University. It would be worthwhile on your part to devote some time and effort to learn the applications you will need to access your course materials, interact with me and your classmates, and submit course requirements. Applications of note are Google Classroom, Google Drive, and Google Meet. There are also available alternatives to Microsoft Office tools you might want to explore. Certain requirements will require you to take a video on your smart phone, save it, and submit it electronically. Work on this skill as well. If you are offline, identify the most convenient means for express mail correspondence and inform me as early as possible so we can make the necessary arrangements ahead of time. 4. MAKE MASTERPIECES. Go beyond minimum requirements. The course learning outcomes will serve as a guide to the minimum expected competencies you are to acquire at the end of this course. It does not limit you from performing beyond it. Keep in mind that the quality of your work reflects the amount of thought and care you put into the process of completing it. It provides a very tangible measure of how much of the competencies you have developed and fully obtained throughout this course. 5. CONNECT CONSTANTLY. There are more than sufficient online and offline modes to ensure that you are well informed and provided on time with the needed learning materials, instructions, requirements, and feedback either from me or from your classmates. Exhaust all means possible to keep in touch and updated. My contact details can be found at the latter part of this document and will be made available and widely disseminated to enrollees of this course. 6. OBSERVE ORIGINALITY. Your course outputs will largely be submitted in electronic form. It is going to have a highly traceable and comparable digital footprint that can be easily checked for originality. Cite your sources properly for referenced statements you decide to use in your own work. Attribute statements by persons other than you by using terms like according to, he said/she said, and the like. 7. INSTIGATE INDEPENDENCE. You are the focus of this course. Nobody else. All assessment and evaluation tools in this course are designed to measure your Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any v means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  competence and not anybody else’s. You may use all resources at your disposal, and ask other people for advice. In the end however, it is going to be your independent work that will be judged against the standards set for this course. The only way for you to maximize this course to your advantage is to learn as much from it as an individual. Make it count. 8. RESPECT THE ROUTINE. There are traditionally respected routines we follow in the conduct of our everyday lives. Please be mindful of universally accepted norms of courtesy attached to regular schedules of personal and family time. Unless of utmost importance, please refrain from any form of communication between 8:30 PM and 7:30 AM every day and the whole day on Sundays and official holidays. You shall expect me to adhere to this guideline myself. This will allow us all to dedicate personal time and space to other aspects of our life and maintain a healthy work-life/study-life balance. 9. FINISH THE FIVE. To be able to help you build your own understanding from experience and new ideas, the modules in this course are designed based on the 5E Instructional Model (Engage, Explore, Explain, Elaborate, and Evaluate). The following icons will help you find some of the most critical areas in the units of the learning modules: Part of module unit that is designed to pique your interest in the topics to be discussed by accessing your prior knowledge and build up your curiosity to learn more. Part of the module unit that presents the main lesson through materials that will give you a general picture of the topics to be discussed, introducing you to new concepts and ideas. Part of the module unit that contains detailed discussions of topics and provide you the definition of the smaller pieces of the general picture you encountered in the previous stage. Part of the module unit that expounds on the ideas of the previous stage and allows you to extrapolate into a broader field or delve deeper into the finer details of the topics. Part of the module unit that gives us the opportunity to gauge your attainment of the learning outcomes using formative and evaluative assessment tools. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any vi means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Additional Guidelines for Offline Students: If you are a student opting for the correspondence-based learning (CBL) mode, you will be tasked to send back the accomplished requirements at given stages of the course through express mail correspondence to me, on or before the scheduled date. I will provide you with the feedback on your submissions at the soonest possible time through any of the available means of communication. While waiting for my feedback of your accomplished requirements, continue doing the tasks in the succeeding units of the module. If needed, do not hesitate to keep in touch with me through any available means. STUDY SCHEDULE TOPIC LEARNING WEEK ACTIVITIES OUTCOME MODULE 1: In Situ Stresses Engage: Determine the distribution of stress throughout an identified cross-section of soil Explore: In Situ Stresses (pp. 271-300) Explain: Understand the Concept of effective stress theoretical August 19- Stresses in saturated soil with different concept of September seepage conditions effective stress and 16, 2020 Seepage force apply it in different Conditions for heaving site scenario. Use of filters Capillary rise in soils Elaborate: Problem Solving Evaluate: Answer assessment questions MODULE 2: Normal and Shear Stresses on a Plane Engage: Determine the normal and shear stresses on a plane Exhibit proficiency Explore: Normal and Shear Stresses on a Plane in using the pole (pp. 306-311) September method to Explain: 17-24, 2020 determine the Normal and Shear Stresses using equations normal and shear Mohr’s Circle stress in a plane. Pole-Method Elaborate: Problem Solving Evaluate: Answer assessment questions September Summative Assessment: PRELIM QUIZ 25, 2020 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any vii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  September Summative Assessment: PRELIM EXAMINATION 28, 2020 SUBMIT YOUR ACCOMPLISHMENTS TO YOUR COURSE LEARNING FACILITATOR ON OR BEFORE OCTOBER 3, 2020 MODULE 3: Stresses in a Soil Mass Engage: Determine the increase in vertical stress due to application of various loadings Explore: Stresses in a Soil Mass (pp. 312-345) Explain: Stresses Caused by Point Load Vertical Stress Caused by a Vertical and Horizontal Line Load Exhibit proficiency Vertical Stress Caused by a Vertical Strip in determining the Load (Finite Width) October 5 - vertical stress in soil Linearly Increasing Vertical Loading on an November under different Infinite Strip 9, 2020 loading conditions Vertical Stress due to Embankment and using different Loading methods. Vertical stress below a Uniformly Loaded Circular Area Vertical stress below a Uniformly Loaded Rectangular Area Influence Chart for Vertical Pressure Elaborate: Problem Solving Evaluate: Answer assessment questions November Summative Assessment: MIDTERM QUIZ 10, 2020 November Summative Assessment: MIDTERM EXAMINATION 12, 2020 SUBMIT YOUR ACCOMPLISHMENTS TO YOUR COURSE LEARNING FACILITATOR ON OR BEFORE NOVEMBER 18, 2020 MODULE 4: Compressibility of Soil Engage: Determine the settlement due to stress Exhibits proficiency increase caused by additional loads in understanding Explore: Compressibility of Soil (pp. 353-420) November the principles of Explain: 19 – consolidation and Elastic Settlement December the step-by-step Primary Consolidation Settlement 2, 2020 process of Secondary Consolidation Settlement computing soil Elaborate: Problem Solving settlements. Evaluate: Answer assessment questions MODULE 5: Shear Strength of Soil Proficiency in the Engage: Determine the shear resistance December determination of parameters of soils which will be used to analyze 3-11, 2020 shear strength soil stability problems determination Explore: Shear Strength of Soil (pp. 429-484) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any viii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  using laboratory Explain: procedures with Mohr-Coulomb Failure Criterion indexes. Direct Shear Test Triaxial Test Unconfined Compression Test Elaborate: Problem Solving Evaluate: Answer assessment questions December Summative Assessment: FINAL QUIZ 14, 2020 December Summative Assessment: FINAL EXAMINATION 15, 2020 SUBMIT YOUR ACCOMPLISHMENTS TO YOUR COURSE LEARNING FACILITATOR ON OR BEFORE DECEMBER 21, 2020 Saint Louis University Calendar for the First Semester AY 2020-2021 Online Registration: August 5-13, 2020 Start of Classes: August 17, 2020 Ninoy Aquino Day: August 21, 2020 (No Classes) National Heroes Day: August 31, 2020 (No Classes) Baguio Foundation Day: September 1, 2020 (No Classes) All Saints’ Day: November 1, 2020 University Foundation Week: November 26 – December 1, 2020 CICM Day: November 26, 2020 Bonifacio Day: November 30, 2020 (No Classes) Immaculate Conception: December 8, 2020 (No Classes) EVALUATION TO PASS THE COURSE, YOU MUST: 1. Read all course readings and answer the pre-assessment quizzes, self-assessment activities and problem sets. 2. Submit two graded quizzes for midterms and finals. 3. Take the Midterm and Final Examination. ASSESSMENT ACTIVITIES Formative Assessment Formative assessments such as self-assessment activities and problem sets aim to enhance and deepen your understanding of the course. The requirements are written after each module and you are expected to submit your output by the scheduled due dates. The honor pledge shall always be a part of all requirements submitted. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any ix means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Summative Assessment Quizzes and Examination – the two graded quizzes will be posted one week before its scheduled date through courier/sms or Google classroom. Midterm and Final Individual assessments will be conducted as scheduled. You will be assigned problems to be answered. The problems will be given through courier/sms or through Google Classroom on the scheduled date of examination. You will have to compile all course requirements including the midterm/final exam and then send it via courier (if printed or saved in USB memory stick or both) or through Google classroom (if electronic file) on or before the deadline. The honor pledge shall always be a part of all requirements submitted. TECHNOLOGICAL TOOLS To be able to accomplish all the tasks in this course, you will be needing the following software applications: Word Processing, Presentation, Publication, and Spreadsheet. These are applications that are available in your desktop or laptops that will not require internet connection for you to use them. Feedback system will be facilitated through text messaging; hence, you need to have with you a cellphone. If you need to call, or you want to talk to me, send me a message first and wait for me to respond. CONTACT INFORMATION OF THE FACILITATOR Engr. Eleazar H. Santiago, MSCE FB account/messenger: Eleazar Hipol Santiago E-mails: [email protected], [email protected] Cellphone No.: 09177169696 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any x means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  TABLE OF CONTENTS TITLE PAGE i COURSE GUIDE............................................................................................................................. iii COURSE OVERVIEW.................................................................................................................................... iii COURSE STUDY GUIDE................................................................................................................. iv STUDY SCHEDULE....................................................................................................................................... vii EVALUATION................................................................................................................................................ ix TECHNOLOGICAL TOOLS........................................................................................................................... x CONTACT INFORMATION OF THE FACILITATOR...................................................................................... x TABLE OF CONTENTS.................................................................................................................... xi MODULE 1: IN - SITU STRESSES (ON - SITE STRESSES).............................................................. 1 ENGAGE................................................................................................................................................. 1 EXPLORE................................................................................................................................................. 1 UNIT 1: TOTAL VERTICAL STRESS FOR SATURATED SOIL (NO SEEPAGE)................................................ 2 EXPLAIN.................................................................................................................................................. 2 ELABORATE............................................................................................................................................ 6 UNIT 2: STRESSES IN SATURATED SOIL WITH SEEPAGE............................................................................. 7 EXPLAIN.................................................................................................................................................. 7 ELABORATE.......................................................................................................................................... 13 UNIT 3: SEEPAGE FORCE........................................................................................................................... 14 EXPLAIN................................................................................................................................................ 14 ELABORATE.......................................................................................................................................... 15 UNIT 4: HEAVING IN SOIL DUE TO FLOW AROUND SHEET PILES.......................................................... 15 EXPLAIN................................................................................................................................................ 15 ELABORATE.......................................................................................................................................... 19 UNIT 5: CAPILLARY RISE IN SOILS............................................................................................................. 19 EXPLAIN................................................................................................................................................ 19 ELABORATE.......................................................................................................................................... 22 EVALUATE............................................................................................................................................. 22 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any xi means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  MODULE 2: NORMAL AND SHEAR STRESSES ON A PLANE.................................................. 23 ENGAGE............................................................................................................................................... 23 EXPLORE............................................................................................................................................... 23 UNIT 1: STRESS EQUATIONS....................................................................................................................... 24 EXPLAIN................................................................................................................................................ 24 ELABORATE.......................................................................................................................................... 29 UNIT 2: MOHR’S CIRCLE............................................................................................................................ 29 EXPLAIN................................................................................................................................................ 29 ELABORATE.......................................................................................................................................... 36 UNIT 3: POLE METHOD............................................................................................................................... 36 EXPLAIN................................................................................................................................................ 36 ELABORATE.......................................................................................................................................... 42 EVALUATE............................................................................................................................................. 42 MODULE 3: STRESSES IN A SOIL MASS.................................................................................... 43 ENGAGE............................................................................................................................................... 43 EXPLORE............................................................................................................................................... 43 UNIT 1: STRESSES CAUSED BY POINT LOAD............................................................................................ 44 EXPLAIN................................................................................................................................................ 44 ELABORATE.......................................................................................................................................... 47 UNIT 2: VERTICAL STRESS CAUSED BY A VERTICAL LINE LOAD............................................................ 47 EXPLAIN................................................................................................................................................ 47 ELABORATE.......................................................................................................................................... 50 UNIT 3: VERTICAL STRESS CAUSED BY A HORIZONTAL LINE LOAD...................................................... 50 EXPLAIN................................................................................................................................................ 50 ELABORATE.......................................................................................................................................... 52 UNIT 4: VERTICAL STRESS CAUSED BY A VERTICAL STRIP LOAD (FINITE WIDTH AND INFINITE LENGTH)...................................................................................................................................................... 52 EXPLAIN................................................................................................................................................ 52 ELABORATE.......................................................................................................................................... 57 UNIT 5: LINEARLY INCREASING VERTICAL LOADING ON AN INFINITE STRIP..................................... 57 EXPLAIN................................................................................................................................................ 57 ELABORATE.......................................................................................................................................... 62 UNIT 6: VERTICAL STRESS DUE TO EMBANKMENT LOADING................................................................ 63 EXPLAIN................................................................................................................................................ 63 ELABORATE.......................................................................................................................................... 70 UNIT 7: VERTICAL STRESS BELOW THE CENTER OF A UNIFORMLY LOADED CIRCULAR AREA.......... 72 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any xii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  EXPLAIN................................................................................................................................................ 72 ELABORATE.......................................................................................................................................... 74 UNIT 8: VERTICAL STRESS AT ANY POINT BELOW A UNIFORMLY LOADED CIRCULAR AREA........... 74 EXPLAIN................................................................................................................................................ 74 ELABORATE.......................................................................................................................................... 77 UNIT 9: VERTICAL STRESS CAUSED BY A RECTANGULAR LOADED AREA........................................... 78 EXPLAIN................................................................................................................................................ 78 ELABORATE.......................................................................................................................................... 83 UNIT 10: VERTICAL STRESS BELOW THE CENTER OF A RECTANGULAR LOADED AREA..................... 84 EXPLAIN................................................................................................................................................ 84 ELABORATE.......................................................................................................................................... 85 UNIT 11: INFLUENCE CHART FOR VERTICAL PRESSURE (NEWMARK’S CHART).................................. 86 EXPLAIN................................................................................................................................................ 86 ELABORATE.......................................................................................................................................... 92 EVALUATE............................................................................................................................................. 92 MODULE 4: COMPRESSIBILITY OF SOIL................................................................................... 93 ENGAGE............................................................................................................................................... 93 EXPLORE............................................................................................................................................... 93 UNIT 1: SETTLEMENT.................................................................................................................................... 94 EXPLAIN................................................................................................................................................ 94 UNIT 2: ELASTIC SETTLEMENT (Se)............................................................................................................. 97 EXPLAIN................................................................................................................................................ 97 ELABORATE........................................................................................................................................ 104 UNIT 3: FUNDAMENTALS OF CONSOLIDATION.................................................................................... 104 EXPLAIN.............................................................................................................................................. 104 ELABORATE........................................................................................................................................ 113 UNIT 4: PRIMARY CONSOLIDATION (SC)............................................................................................... 113 EXPLAIN.............................................................................................................................................. 113 ELABORATE........................................................................................................................................ 116 UNIT 5: SECONDARY CONSOLIDATION (SS)........................................................................................ 116 EXPLAIN.............................................................................................................................................. 116 ELABORATE........................................................................................................................................ 119 UNIT 6: TIME RATE OF CONSOLIDATION............................................................................................... 119 EXPLAIN.............................................................................................................................................. 119 ELABORATE........................................................................................................................................ 125 EVALUATE........................................................................................................................................... 125 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any xiii means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  MODULE 5: SHEAR STRENGTH OF SOIL................................................................................. 126 ENGAGE............................................................................................................................................. 126 EXPLORE............................................................................................................................................. 126 UNIT 1: MOHR – COULOMB FAILURE CRITERION................................................................................. 127 EXPLAIN.............................................................................................................................................. 127 UNIT 2: DIRECT SHEAR TEST..................................................................................................................... 130 EXPLAIN.............................................................................................................................................. 130 ELABORATE........................................................................................................................................ 135 UNIT 3: TRIAXIAL SHEAR TEST-GENERAL................................................................................................ 135 EXPLAIN.............................................................................................................................................. 135 UNIT 4: CONSOLIDATED-DRAINED (CD) TRIAXIAL TEST...................................................................... 137 EXPLAIN.............................................................................................................................................. 137 ELABORATE........................................................................................................................................ 142 UNIT 5: CONSOLIDATED-UNDRAINED (CU) TRIAXIAL TEST................................................................. 142 EXPLAIN.............................................................................................................................................. 142 ELABORATE........................................................................................................................................ 145 UNIT 6: UNCONSOLIDATED-UNDRAINED (UU) TRIAXIAL TEST............................................................ 145 EXPLAIN.............................................................................................................................................. 145 UNIT 7: UNCONFINED COMPRESSION TEST ON SATURATED CLAY................................................... 146 EXPLAIN.............................................................................................................................................. 146 ELABORATE........................................................................................................................................ 148 EVALUATE........................................................................................................................................... 148 REFERENCE................................................................................................................................ 149 ASSIGNMENT GUIDE................................................................................................................ 149 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any xiv means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  MODULE 1: IN - SITU STRESSES (ON - SITE STRESSES) ENGAGE For various geotechnical engineering problems, we need to analyze and determine the nature of stress distribution along an identified soil profile cross-section. As described from the course CE 412: Geotechnical Engineering 1, the soil is a multiphase system. Recall your learnings and answer the following questions by writing your answers in the space provided. 1. What are the different components of soil? 2. What are the different weight and volume relationship parameters in determining the soil unit weight? 3. What are the different types of soil unit weight? 4. What might be the impact of layers of soil in total weight? This module includes the concept of effective stress, stresses in saturated soil with different seepage conditions, seepage force, conditions for heaving, use of filters, and capillary rise in soils. EXPLORE Read: In Situ Stresses (pp. 271-299) Das B.M., and Sobhan, K. (2014) Principles of Geotechnical Engineering, 8th ed. United States: Cengage Learning Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 1 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 1: TOTAL VERTICAL STRESS FOR SATURATED SOIL (NO SEEPAGE) EXPLAIN Total Stress, σ - Total weight of the soil column - It includes all the components, such as weight of soil solids and water (weight of air is negligible) σ = Σ(γH) (1.1) where: γ = unit weight of the material, H = height/depth of the material The total stress therefore for point A along the section a – a for Figure 1.1. is: σA = γw H + γsat (HA − H) (1.2) Components of total stress: σ = u + σ′ (1.3) 1. Water in the void space, u - hydrostatic pressure - pore water pressure - neutral stress u = γw h (1.4) where: γw = unit weight of water sample from Figure 1.1.: Figure 1.1. Saturated soil column uA = γw HA (1.5) without seepage 2. Soil solids at their points of contact, σ’ - effective vertical stress σ′ = σ − u (1.6) For the effective stress at sample point A, using equation 1.6, substitute equations 1.2 and 1.5: σ′A = γw H + γsat HA − γsat H − γw HA (1.7) σA uA Consider terms with same type of unit weight and extract -1 for γw group: σ′A = γsat (HA − H) − γw ( HA − H) (1.8) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 2 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Extract (H-HA): σ′A = (γsat − γw )(HA − H) (1.9) Effective Soil Unit Weight Depth of the soil Effective Soil Unit Weight, γ’ - submerged unit weight γ′ = γsat − γw (1.10) Effective Vertical Stress, σ’ σ′ = Σ(γ′H) (1.11) Notes: - The stress acting for a certain point is the weight above it - For layers of soil (total and effective), apply summation of stresses from free surface (sample: ground level) to the sample point - For dry soil, consider effective unit weight = dry unit weight - Better to present computations in table form Sample Problems: 9.3 A soil profile consisting of three layers is shown in Figure 1.2. Calculate the values of σ, ] 300 u, and σ’ at points A, B, C, and D. In each case, plot the variations of σ, u, and σ’ with depth. Figure 1.2 Solution: Processes: 1. In table form, identify the different points (at the surface/interface of different layers) 2. Use equations 1.1 for σ, 1.4 for u, and 1.6 (or 1.11) for σ’ Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 3 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  σ u σ' Points (Eq. 1.1) (Eq. 1.4) (Eq. 1.6) (Eq. 1.11) 0 (no load above A 0 (no ground 0 0 (no load above A) A) water present kN kN (16 3 ) (3m) above the (16 ) (3m) B m 48 kPa m3 sample point) = 48 kPa = 48 kPa 48 kPa kN kN kN (9.81 ) (6m) 48 kPa + (18 − 9.81) (6m) C + (18 3 ) (6m) m3 97.14 kPa m3 m = 58.86 kPa = 97.14 kPa = 156 kPa 156 kPa kN 97.14 kPa kN (9.81 3 ) (8.5m) 115.115 kN D + (17 3 ) (2.5m) m + (17 − 9.81) (2.5m) m kPa m3 = 83.385 kPa = 198.5 kPa = 115.115 kPa Must be equal Stress Diagrams: σ u σ′ 0 0 0 48 kPa 0 48 kPa 156 kPa 58.86 kPa 97.14 kPa 198.5 kPa 83.385 kPa 115.115 kPa z z z Figure 1.3 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 4 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  9.5 Consider the soil profile shown in Figure 1.4: ] 301 a. Calculate the effective stress at C (modified requirement). b. How high should the groundwater table rise/drop so that the effective stress at C is 111 kN/m2? Figure 1.4 Solution: Determine first the unit weight of the two layers: - Dry Sand: kN Gs γw (2.66) (9.81 m3 ) kN γd = = = 16.208 3 1+e 1 + 0.61 m - Saturated Sand kN Gs γw + eSγw (Gs + eS)γw (2.67 + 0.48) (9.81 m3 ) kN γsat = = = = 20.879 3 1+e 1+e 1 + 0.48 m a. Effective Stress at C: Method 1: Total Stress at C (Eq. 1.1): kN kN σC = Σ(γH) = (16.208 m3 ) (4m) + (20.879 m3 ) (5m) = 169.227 kPa Pore water pressure at C (Eq. 1.4): kN uC = γw h = (9.81 m3 ) (5m) = 49.05 kPa Effective stress at C (Eq. 1.6): σ′C = σC − uC = 169.227 kPa − 49.05 kPa = 120.177 kPa Method 2: Effective stress at C (Eq. 1.11): kN kN σ′C = Σ(γ′ H) = (16.208 3 ) (4m) + (20.879 − 9.81 3 ) (5m) = 120.177 kPa m m Note for the changes of effective stress value: - If the effective stress increases (↑) = the ground water table surface drop (↓) - If the effective stress decreases (↓) = the ground water table surface rise (↑) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 5 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  b. Rise/drop in the depth of the ground water table, x Comparing the initial effective stress with the new effective stress: initial effective stress ? new effective stress 120.177 kPa > 111 kPa - decreases, therefore ground water table surface rise Solve the unit weight of the portion of Layer 1 converted from dry to saturated condition: x γsat = Gs γw + eSγw (Gs + eS)γw = 1+e 1+e kN (2.66 + 0.61) (9.81 3 ) = m 1 + 0.61 kN = 19.925 3 m Figure 1.5 Effective stress at C (Eq. 1.11): σ′C = Σ(γ′ H) kN kN kN kN 111 2 = (16.208 3 ) (4m − x) + (19.925 − 9.81 3 ) (x) + (20.879 − 9.81 3 ) (5m) m m m m x =1.506 m ELABORATE Try solving the following problems: Practice Problem 1: Consider the soil profile shown in Figure 1.4: How high should the groundwater table rise/drop so that the effective stress at C is 130 kN/m2? Practice Problem 2: A soil profile consisting of three layers is shown in Figure 1.6. Calculate the values of σ, u, and σ’ at points A, B, C, and D. In each case, plot the variations of σ, u, and σ’ with depth. Figure 1.6 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 6 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 2: STRESSES IN SATURATED SOIL WITH SEEPAGE EXPLAIN Effect of Seepage: - Effective stress will change at any point (increase or decrease) depending on the direction of seepage o Due to the increase or decrease of pore water pressure Upward Seepage Without Seepage (a) (b) Figure 1.7. Layer of soil in tank with upward seepage The impact of seepage will be analyzed using the concept of: Hydraulic Gradient head loss h 𝐢= = (1.12) distance between points H2 - the modification will be for the value of the pore water pressure - same computation for total and effective stresses Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 7 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Table 1.1. Variations of Stresses for Soil with Upward Seepage 𝛔 𝐮 𝛔′ Points (Eq. 1.1) (Eq. 1.4) (Eq. 1.6) A γw H1 γw H1 0 γsat z − γw z − γw iz B γw H1 + γsat z γw (H1 + z + iz) = (γsat − γw )z − γw iz = γ′ z − γw iz γsat H2 − γw H2 − γw h C γw H1 + γsat H2 γw (H1 + H2 + h) = (γsat − γw )H2 − γw h = γ′H2 −γw h Boiling or Quick Condition  When the rate of seepage and hydraulic gradient gradually are increased  Limiting condition will be reached  Soil stability is lost For critical condition: effective stress, σ’ = 0, thus σ = u σ′c = γ′ z − γw icr z = 0 (1.13) γ′ icr = (1.14) γw for most soils: icr ≈ 0.9 – 1.1, with average of 1 failure if: i > icr Factor of Safety, Fs For critical condition: effective stress, σ’ = 0, thus σ = u strength or resisting value (downward force/load) Factor of Safety = (1.15) stress or generator of failure (upward force) σ Fs = (1.16) u Fs > 1 (safe), Fs = 1 (critical), Fs < 1 (unsafe) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 8 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Downward Seepage Without Seepage (a) (b) Figure 1.8. Layer of soil in tank with downward seepage The impact of seepage will be analyzed using the concept of Hydraulic Gradient using Eq.1.12 - the modification will be for the value of the pore water pressure - same computation for total and effective stresses Table 1.2. Variations of Stresses for Soil with Downward Seepage 𝛔 𝐮 𝛔′ Points (Eq. 1.1) (Eq. 1.4) (Eq. 1.6) A γw H1 γw H1 0 γsat z − γw z − γw iz B γw H1 + γsat z γw (H1 + z − iz) = (γsat − γw )z − γw iz = γ′ z + γw iz γsat H2 − γw H2 − γw h C γw H1 + γsat H2 γw (H1 + H2 − h) = (γsat − γw )H2 − γw h = γ′H2 +γw h Note for the soil with seepage as shown in Tables 1.1 and 1.2: - upward seepage (↑) = the effective stress decreases (↓) - downward seepage (↓) = the effective stress increases (↑) Sample Problems: 9.7 An exploratory drill hole was made in a stiff saturated clay having a moisture content ] 301 of 29% and Gs = 2.68 as shown in Figure 1.9a. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 6 m Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 9 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  above the top of sand layer. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom heaves. (a) (b) Figure 1.9 Required: H (safe cut) Solution: Determine the unit weight of the stiff saturated clay: Gs w = eS, (S = 1 for saturated soils) e = Gs w = 2.68(0.29) = 0.7772 kN Gs γw + eSγw (Gs + eS)γw (2.68 + 0.7772) (9.81 m3 ) kN γsat = = = = 19.083 3 1+e 1+e 1 + 0.7772 m Total Stress at the bottom of the stiff soil (Eq 1.1): kN σ = Σ(γH) = (19.083 ) (10m − H) m3 Pore water pressure at the bottom of the stiff soil (Eq. 1.4): kN u = γw h = (9.81 m3 ) (6m) = 58.86 kPa For critical condition: effective stress, σ’ = 0, thus σ = u kN (19.083 3 ) (10m − H) = 58.86 kPa m H < 6.916 m (if the problem asks determine the maximum/critical depth of excavation, then the answer must be H = 6.916m) 9.8 A 10-m-thick layer of stiff saturated clay is underlain by a layer of sand as shown in ] 302 Figure 1.10. The sand is under artesian pressure. A 5.75-m-deep cut is made in the clay. Determine the factor of safety against heaving at point A. Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 10 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  Figure 1.10 Required: Fs Solution: Determine the saturated unit weight: kg m N kN γsat = ρsat (g) = 1925 3 (9.81 2 ) = 18884.25 3 = 18.884 3 m s m m Factor of safety (Eq. 1.16): kN σ γsat H (18.884 m3 ) (10m − 5.75m) Fs = = = = 1.363 > 1 (safe) u γw h kN (9.81 3 ) (6m) m 9.9 Refer to the Figure 1.10. What would be the maximum permissible depth of cut before ] 302 heaving would occur? Required: H (maximum/critical) Solution: Total Stress at the bottom of the stiff soil (Eq 1.1): kN σ = Σ(γH) = (18.884 3 ) (10m − H) m Pore water pressure at the bottom of the stiff soil (Eq. 1.4): kN u = γw h = (9.81 3 ) (6m) = 58.86 kPa m For critical condition: effective stress, σ’ = 0, thus σ = u kN (18.884 3 ) (10m − H) = 58.86 kPa m H = 6.883 m Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 11 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  9.10 Refer to Problem 9.9. Water may be introduced into the cut to improve the stability ] 302 against heaving. Assuming that a cut is made up to the maximum permissible depth calculated in Problem 9.9, what would be the required height of water inside the cut in order to ensure a factor of safety of 1.5? Required: hw inside the cut (infiltration is not permitted because the soil is stiff clay/impermeable) Solution: Total Stress at the bottom of the stiff soil (Eq 1.1): kN kN σ = Σ(γH) = (18.884 3 ) (10m − 6.883m) + (9.81 3 ) (hw ) m m Pore water pressure at the bottom of the stiff soil (Eq. 1.4): kN u = γw h = (9.81 3 ) (6m) = 58.86 kPa m Factor of safety (Eq. 1.16): kN kN σ (18.884 m3 ) (10m − 6.883m) + (9.81 m3 ) (hw ) Fs = 1.5 = = u 58.86 kPa hw ≈ 3 m 9.12 Refer to Figure 1.7b. If H1 = 0.91 m, H2 = 1.37 m, h = 0.46 m, γsat = 18.67 kN/m3, area of ] 302 the tank = 0.58 m2, and hydraulic conductivity of the sand (k) = 0.16 cm/sec, a. What is the rate of upward seepage of water (m3/min)? b. If the point C is located at the middle of the soil layer, then what is the effective stress at C? Solution: a. rate of upward seepage, q = kiA (from CE 412) Hydraulic gradient (Eq. 1.12): loss h (head gain) 0.46 m i= = = 0.336 L (distance travelled by water particle through the soil medium) 1.37 m cm 1m 60 sec m3 q = (0.16 ) (0.336)(0.58 m2 ) ( )( ) = 0.019 sec 100cm 1 min. min b. Effective Stress at point C, using the equation from Table 1.1: kN 1.37m kN 1.37m σ′C = γ′ z − γw iz = (18.67 − 9.81) 3 ( ) − (9.81 3 ) (0.336) ( ) = 3.811 kPa m 2 m 2 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 12 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  ELABORATE Try solving the following problems: Practice Problem 1: An exploratory drill hole was made in a stiff saturated clay having a moisture content of 15% and Gs = 2.8 as shown in Figure 1.11. The sand layer underlying the clay was observed to be under artesian pressure. Water in the drill hole rose to a height of 8 m above the top of sand layer. If an open excavation is to be made in the clay, determine the safe depth of excavation before the bottom heaves. Figure 1.11 Practice Problem 2: Refer to Figure 1.12. If H1 = 1.5 m, H2 = 2.5 m, h = 1.5 m, e =0.49, Gs = 2.66, area of the tank = 0.62 m2, and hydraulic conductivity of the sand (k) = 0.21 cm/sec. a. What is the rate of upward seepage of water (m3/min)? b. Will boiling occur when h = 1.5 m? c. What would be the critical value of h to cause boiling? Figure 1.12 Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 13 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  UNIT 3: SEEPAGE FORCE EXPLAIN Seepage Force  Force is equal to the soil stress multiplied to the area no seepage P’1 = with upward seepage P’2 = with downward seepage Figure 1.13. Force on a volume of soil due to (a) no seepage, (b) upward seepage, and (c) downward seepage From Figure 1.13a: P1′ = zγ′ A (1.17) From Figure 1.13b: P2′ = (zγ′ − izγw )A (1.18) The seepage force = decrease (or increase) in the total force due to seepage: P1′ − P2′ = γ′ zA − (γ′ z − γ𝑤 iz)A = γ𝑤 𝑖𝑧𝐴 (1.19) Property of and for the exclusive use of SLU. Reproduction, storing in a retrieval system, distributing, uploading or posting online, or transmitting in any form or by any 14 means, electronic, mechanical, photocopying, recording, or otherwise of any part of this document, without the prior written permission of SLU, is strictly prohibited.  If vol. = volume of the contri