The unconfined compression test is a type of unconsolidated-undrained test used for clay specimens. It involves compressing a cylindrical clay sample axially without lateral confinement. The major principal stress is the axial stress, while the minor principal stresses are zero. This allows measuring the unconfined compressive strength, sensitivity, shear strength parameters, and cohesion of cohesive soils. The test procedure involves extruding and trimming a soil specimen, measuring it, and compressing it at a controlled strain rate between loading plates while recording the load and stress. Parameters are calculated based on the failure load and specimen dimensions.
The document discusses soil consolidation and laboratory consolidation testing. It begins with an introduction to consolidation and describes the three types of soil settlement: immediate elastic settlement, primary consolidation settlement, and secondary consolidation settlement. It then discusses consolidation in more detail, including the spring-cylinder model used to demonstrate consolidation principles. Finally, it describes the process and components of a laboratory oedometer consolidation test.
The document discusses shear strength of soils. It defines shear strength as the soil's resistance to shearing stresses and deformation from particle displacement. Shear strength depends on cohesion between particles and frictional resistance, as modeled by the Mohr-Coulomb failure criterion. Laboratory tests like direct shear and triaxial shear tests are used to determine the shear strength parameters (c, φ) that describe a soil's failure envelope.
1. The standard penetration test (SPT) involves driving a split-spoon sampler into the ground using a 63.5 kg hammer dropped from a height of 0.76 m. The number of blows required to drive the sampler over two intervals of 150 mm each is recorded as the SPT N-value.
2. The SPT N-value provides an approximate measure of soil resistance and a disturbed soil sample. It can be used to estimate soil strength parameters and bearing capacity through empirical correlations.
3. However, the SPT is highly dependent on the equipment and operator used, as factors like hammer efficiency, drill rod length, and borehole diameter can affect the N-value. Corrections are required
The document discusses effective stress in soils. It defines total stress, pore water pressure, and effective stress. Total stress is the load carried by the soil grains and water. Pore water pressure depends on depth and water flow conditions. Effective stress is the difference between total stress and pore water pressure, and represents the stress carried by the soil skeleton. Effective stress applies to saturated soils and influences properties like compressibility and consolidation. It is an imaginary parameter that cannot be directly measured but is important in soil mechanics analyses.
This document discusses soil mechanics concepts related to lateral earth pressure. It defines active and passive earth pressures and describes Rankine's theory and assumptions for calculating lateral pressures on retaining walls. Equations are provided for determining active and passive earth pressure coefficients and distributions for cohesionless and cohesive soils. The effects of groundwater, surcharges, and sloping backfills are also examined. Sample problems are included to calculate lateral earth pressures and forces on retaining walls for different soil and loading conditions.
This document is a series of lecture slides from Assistant Professor Khalid R. Mahmood at the University of Anbar in Iraq-Ramadi on the topic of effective stress concepts in soil mechanics. It introduces key concepts such as effective stress, total stress, pore water pressure, and their relationships. It also discusses effective stress in saturated soil with and without seepage, seepage forces, filter requirements, capillary rise in soil, and two example problems calculating stresses with depth.
Compaction of soil involves mechanically rearranging soil particles to reduce voids and increase dry density, which improves engineering properties like strength and reduces settlement. Standard compaction tests determine the optimum water content and maximum dry density for a given soil and compactive effort. Factors like water content, compactive effort, soil type, and method of compaction influence the engineering behavior of compacted soils.
The document discusses soil consolidation and laboratory consolidation testing. It begins with an introduction to consolidation and describes the three types of soil settlement: immediate elastic settlement, primary consolidation settlement, and secondary consolidation settlement. It then discusses consolidation in more detail, including the spring-cylinder model used to demonstrate consolidation principles. Finally, it describes the process and components of a laboratory oedometer consolidation test.
The document discusses shear strength of soils. It defines shear strength as the soil's resistance to shearing stresses and deformation from particle displacement. Shear strength depends on cohesion between particles and frictional resistance, as modeled by the Mohr-Coulomb failure criterion. Laboratory tests like direct shear and triaxial shear tests are used to determine the shear strength parameters (c, φ) that describe a soil's failure envelope.
1. The standard penetration test (SPT) involves driving a split-spoon sampler into the ground using a 63.5 kg hammer dropped from a height of 0.76 m. The number of blows required to drive the sampler over two intervals of 150 mm each is recorded as the SPT N-value.
2. The SPT N-value provides an approximate measure of soil resistance and a disturbed soil sample. It can be used to estimate soil strength parameters and bearing capacity through empirical correlations.
3. However, the SPT is highly dependent on the equipment and operator used, as factors like hammer efficiency, drill rod length, and borehole diameter can affect the N-value. Corrections are required
The document discusses effective stress in soils. It defines total stress, pore water pressure, and effective stress. Total stress is the load carried by the soil grains and water. Pore water pressure depends on depth and water flow conditions. Effective stress is the difference between total stress and pore water pressure, and represents the stress carried by the soil skeleton. Effective stress applies to saturated soils and influences properties like compressibility and consolidation. It is an imaginary parameter that cannot be directly measured but is important in soil mechanics analyses.
This document discusses soil mechanics concepts related to lateral earth pressure. It defines active and passive earth pressures and describes Rankine's theory and assumptions for calculating lateral pressures on retaining walls. Equations are provided for determining active and passive earth pressure coefficients and distributions for cohesionless and cohesive soils. The effects of groundwater, surcharges, and sloping backfills are also examined. Sample problems are included to calculate lateral earth pressures and forces on retaining walls for different soil and loading conditions.
This document is a series of lecture slides from Assistant Professor Khalid R. Mahmood at the University of Anbar in Iraq-Ramadi on the topic of effective stress concepts in soil mechanics. It introduces key concepts such as effective stress, total stress, pore water pressure, and their relationships. It also discusses effective stress in saturated soil with and without seepage, seepage forces, filter requirements, capillary rise in soil, and two example problems calculating stresses with depth.
Compaction of soil involves mechanically rearranging soil particles to reduce voids and increase dry density, which improves engineering properties like strength and reduces settlement. Standard compaction tests determine the optimum water content and maximum dry density for a given soil and compactive effort. Factors like water content, compactive effort, soil type, and method of compaction influence the engineering behavior of compacted soils.
- Soils fail primarily in shear when the shear stress along a failure plane reaches the soil's shear strength.
- The shear strength of soils is governed by the Mohr-Coulomb failure criterion, which consists of cohesive and frictional components that can be determined through laboratory tests such as direct shear and triaxial shear tests.
- These laboratory tests aim to simulate the in-situ stress conditions on soil samples and measure the shear stress and normal stress at failure to establish the shear strength parameters (c, φ) from the failure envelope.
This document provides an overview of slope stability and analysis. It defines different types of slopes as natural, man-made, infinite and finite. Common causes of slope failure like erosion, seepage, drawdown, rainfall, earthquakes and external loading are described. Key terms used in slope stability are defined, including slip zone, slip plane, sliding mass and slope angle. Types of slope failures are identified as face/slope failure, toe failure and base failure. Methods for analyzing finite slope stability, like Swedish circle method, Bishop's simplified method and Taylor's stability number are introduced. Infinite slope analysis is described for cohesionless, cohesive and cohesive-frictional soils. Example tutorial problems on slope stability calculations are
This document discusses the consolidation of soil. It defines important terms like compression, compressibility, and consolidation. It outlines the differences between compaction and consolidation. The importance of consolidation theory is that it provides information on total settlement, time for settlement, and types of settlement. Terzaghi's spring analogy is described to explain the consolidation process. A one-dimensional consolidation test procedure is outlined. Important definitions related to consolidation like compression index, swelling index, and coefficients are provided. The document also discusses normally, under, and over consolidated soils and how to determine preconsolidation pressure. Terzaghi's one-dimensional consolidation theory and solution are presented. Methods to determine degree of consolidation and coefficient of consolidation from laboratory test data are
The document provides information about shear strength of soil. It defines shear strength and its components of cohesion and internal friction. It discusses Mohr's circle of stress and Mohr-Coulomb theory for shear strength. The types of soil are classified based on drainage conditions during shear testing. Common shear strength tests like direct shear test, triaxial test, unconfined compression test and vane shear test are also explained. Sample calculations for shear strength determination from test results are presented.
Bearing capacity of shallow foundations by abhishek sharma ABHISHEK SHARMA
elements you should know about bearing capacity of shallow foundations are included in it. various indian standards are also used. Bearing capacity theories by various researchers are also included. numericals from GATE CE and ESE CE are also included.
SHEAR STRENGTH THEORY
the shear strength of any material is the load per unit area or pressure that it can withstand before undergoing shearing failure.
The standard penetration test (SPT) involves driving a split spoon sampler into the ground using a 140 lb hammer dropped 30 inches. The number of blows required to penetrate each 6 inch interval is recorded, and the penetration resistance value N is the sum of the blows over the second and third intervals. This test is commonly used to obtain bearing capacity and estimate soil properties like density and shear strength. It is performed whenever the soil stratum changes and at intervals of no more than 1.5 meters.
- Soils fail primarily in shear when the shear stress along a failure plane reaches the soil's shear strength.
- The shear strength of soils is governed by the Mohr-Coulomb failure criterion, which consists of cohesive and frictional components that depend on effective stresses.
- Laboratory tests like direct shear and triaxial tests are used to measure the shear strength parameters (c, φ) of soils by simulating the in-situ stress conditions.
Class notes of Geotechnical Engineering course I used to teach at UET Lahore. Feel free to download the slide show.
Anyone looking to modify these files and use them for their own teaching purposes can contact me directly to get hold of editable version.
This document discusses subsoil exploration, which involves collecting soil data through field and laboratory investigations to assess soil properties at a site. The main objectives are to determine the nature, depth, thickness, and extent of soil strata, as well as groundwater depth and properties. Exploration methods include direct techniques like test pits and borings, and indirect techniques like sounding tests and geophysical methods. Standard penetration tests are commonly used to determine properties of cohesionless soils by counting blows required to penetrate the soil. Corrections are applied to penetration values to account for overburden pressure and sample dilatancy.
Best numerical problem group pile capacity (usefulsearch.org) (useful search)Make Mannan
A circular well with an external diameter of 4.5m and steel thickness of 0.75m is embedded 12m deep in uniform sand. The sand has an angle of internal friction of 30 degrees and submerged unit weight of 1 t/m3. The well is subjected to a horizontal force of 50t and bending moment of 400tm at the scour level. Assuming the well acts as a lightweight retaining wall, the allowable total equivalent resting force due to earth pressure with a safety factor of 2 is calculated.
A group of 16 square piles extends 12 m into stiff clay soil, underlain by rock at 24 m depth. Pile dimensions are 0.3 m x 0.3 m. Undrained shear strength of clay increases linearly from 50 kPa at surface to 150 kPa at rock. Factor of safety for group capacity is 2.5. Determine group capacity and individual pile capacity.
The group capacity is calculated to be 1600 kN. The individual pile capacity is determined to be 100 kN. The factor of safety of 2.5 is then applied to determine the safe load capacity.
- There are four main methods to measure the load carrying capacity of piles: static methods, dynamic formulas, in-situ penetration tests, and pile load tests.
- The ultimate load capacity (Qu) of an individual pile or pile group equals the sum of the point resistance (Qp) at the pile tip and the shaft resistance (Qs) developed along the pile shaft through friction between the soil and pile.
- Meyerhof's method is commonly used to calculate Qp in sand based on the effective vertical pressure at the pile tip multiplied by the bearing capacity factor Nq.
Lecture 11 Shear Strength of Soil CE240Wajahat Ullah
Shear Strength of Soil
Shear strength in soils
Introduction
Definitions
Mohr-Coulomb criterion
Introduction
Lab tests for getting the shear strength
Direct shear test
Introduction
Procedure & calculation
Critical void ratio
This document discusses lateral earth pressure and provides details on Rankine's theory and graphical methods for determining active and passive earth pressures. It explains that lateral earth pressure is exerted by soil on retaining structures and depends on whether the structure is stationary or moving towards/away from the soil mass. Rankine's theory assumes dry, homogeneous soil and a vertical wall. Rebhann and Culmann's graphical methods can be used to locate the failure plane and determine the magnitude and direction of lateral earth pressures based on the soil's friction angle and the structure's orientation.
This document discusses settlement of structures. It defines settlement as the vertical downward movement of a structure resulting from deformation of the supporting soil. Settlement includes three components: immediate/elastic settlement occurring within 7 days; primary consolidation settlement over time as pore water is expelled from saturated soils; and secondary compression of the soil skeleton. Differential settlement occurs when different parts of a structure settle by different amounts, potentially causing tilting. Common causes of settlement include excessive structural loads, weak soil compaction, changing groundwater levels, transpiration by plants, earthquakes, and drainage issues. Foundations must be designed to support dead loads, live loads, wind loads, and seismic loads without exceeding the soil's safe bearing capacity.
This document provides 10 examples of problems related to bearing capacity of foundations. The examples calculate bearing capacity using Terzaghi's analysis for different soil and foundation conditions, including cohesionless and cohesive soils, square and strip footings, and considering the water table depth. One example compares results to field plate load tests. The solutions show calculations for determining soil shear strength parameters, factor of safety, and safe bearing capacity.
This document summarizes bearing capacity theory for shallow foundations. It defines key terms like ultimate, net ultimate, and safe bearing capacities. It describes Terzaghi's bearing capacity equation, which considers soil shear strength parameters (c, φ), surcharge loads, and bearing capacity factors (Nc, Nq, Nr). It outlines the failure geometry Terzaghi assumed, with five distinct failure zones. It also distinguishes between general shear, local shear, and punching shear failures based on soil properties and characteristics. Empirical modifications are suggested for local shear failures. Charts summarize the bearing capacity equations for different shaped footings based on experimental results.
This document discusses preconsolidation pressure in soils. It defines preconsolidation pressure as the maximum effective vertical overburden stress a soil sample has experienced in the past. Though it cannot be directly measured, it can be estimated using methods like analyzing the curvature of a consolidation curve. A soil is considered normally consolidated if the current vertical effective stress is equal to or greater than the preconsolidation pressure. The document also lists factors that can cause a soil to approach its preconsolidation pressure, such as changes in total stress, pore water pressure, soil structure, or environmental conditions. Finally, it states that knowing the preconsolidation pressure is important for predicting settlement, site preparation for construction, and determining appropriate
This presentation includes Definition of Permeability, measurement of Permeability, Validity of Darcy's law, Darcy's Law, Methods of Finding Permeability, factors affecting permeability, Permeability of Stratified Soil
FIELD TEST FOR BEARING CAPACITY-revised for BC.pptxsbarai0802
This document discusses various field tests used to determine bearing capacity of soils, including the standard penetration test (SPT), plate load test, cone penetration test (CPT), and pressure meter test. The SPT involves driving a split spoon sampler into the ground using a hammer and measuring the blow counts, while corrections are applied to the observed value. The plate load test applies incremental loads to a steel plate in a pit until a maximum settlement is reached to determine ultimate bearing capacity. The CPT provides continuous measurements of cone resistance with depth to assess soil properties. The pressure meter test measures volume changes in a probe under increasing gas pressure to identify elastic and plastic soil behavior.
1) The document provides notes on soil mechanics topics written by Saqib Imran, a civil engineering student in Peshawar, Pakistan.
2) It includes definitions of soil mechanics, descriptions of soil testing methods like the unconfined compression test, and explanations of soil mechanics concepts like active earth pressure on retaining walls.
3) The notes are intended to help other students and engineers working in the field to gain knowledge on soil mechanics subjects. Saqib provides his contact information for anyone with questions.
- Soils fail primarily in shear when the shear stress along a failure plane reaches the soil's shear strength.
- The shear strength of soils is governed by the Mohr-Coulomb failure criterion, which consists of cohesive and frictional components that can be determined through laboratory tests such as direct shear and triaxial shear tests.
- These laboratory tests aim to simulate the in-situ stress conditions on soil samples and measure the shear stress and normal stress at failure to establish the shear strength parameters (c, φ) from the failure envelope.
This document provides an overview of slope stability and analysis. It defines different types of slopes as natural, man-made, infinite and finite. Common causes of slope failure like erosion, seepage, drawdown, rainfall, earthquakes and external loading are described. Key terms used in slope stability are defined, including slip zone, slip plane, sliding mass and slope angle. Types of slope failures are identified as face/slope failure, toe failure and base failure. Methods for analyzing finite slope stability, like Swedish circle method, Bishop's simplified method and Taylor's stability number are introduced. Infinite slope analysis is described for cohesionless, cohesive and cohesive-frictional soils. Example tutorial problems on slope stability calculations are
This document discusses the consolidation of soil. It defines important terms like compression, compressibility, and consolidation. It outlines the differences between compaction and consolidation. The importance of consolidation theory is that it provides information on total settlement, time for settlement, and types of settlement. Terzaghi's spring analogy is described to explain the consolidation process. A one-dimensional consolidation test procedure is outlined. Important definitions related to consolidation like compression index, swelling index, and coefficients are provided. The document also discusses normally, under, and over consolidated soils and how to determine preconsolidation pressure. Terzaghi's one-dimensional consolidation theory and solution are presented. Methods to determine degree of consolidation and coefficient of consolidation from laboratory test data are
The document provides information about shear strength of soil. It defines shear strength and its components of cohesion and internal friction. It discusses Mohr's circle of stress and Mohr-Coulomb theory for shear strength. The types of soil are classified based on drainage conditions during shear testing. Common shear strength tests like direct shear test, triaxial test, unconfined compression test and vane shear test are also explained. Sample calculations for shear strength determination from test results are presented.
Bearing capacity of shallow foundations by abhishek sharma ABHISHEK SHARMA
elements you should know about bearing capacity of shallow foundations are included in it. various indian standards are also used. Bearing capacity theories by various researchers are also included. numericals from GATE CE and ESE CE are also included.
SHEAR STRENGTH THEORY
the shear strength of any material is the load per unit area or pressure that it can withstand before undergoing shearing failure.
The standard penetration test (SPT) involves driving a split spoon sampler into the ground using a 140 lb hammer dropped 30 inches. The number of blows required to penetrate each 6 inch interval is recorded, and the penetration resistance value N is the sum of the blows over the second and third intervals. This test is commonly used to obtain bearing capacity and estimate soil properties like density and shear strength. It is performed whenever the soil stratum changes and at intervals of no more than 1.5 meters.
- Soils fail primarily in shear when the shear stress along a failure plane reaches the soil's shear strength.
- The shear strength of soils is governed by the Mohr-Coulomb failure criterion, which consists of cohesive and frictional components that depend on effective stresses.
- Laboratory tests like direct shear and triaxial tests are used to measure the shear strength parameters (c, φ) of soils by simulating the in-situ stress conditions.
Class notes of Geotechnical Engineering course I used to teach at UET Lahore. Feel free to download the slide show.
Anyone looking to modify these files and use them for their own teaching purposes can contact me directly to get hold of editable version.
This document discusses subsoil exploration, which involves collecting soil data through field and laboratory investigations to assess soil properties at a site. The main objectives are to determine the nature, depth, thickness, and extent of soil strata, as well as groundwater depth and properties. Exploration methods include direct techniques like test pits and borings, and indirect techniques like sounding tests and geophysical methods. Standard penetration tests are commonly used to determine properties of cohesionless soils by counting blows required to penetrate the soil. Corrections are applied to penetration values to account for overburden pressure and sample dilatancy.
Best numerical problem group pile capacity (usefulsearch.org) (useful search)Make Mannan
A circular well with an external diameter of 4.5m and steel thickness of 0.75m is embedded 12m deep in uniform sand. The sand has an angle of internal friction of 30 degrees and submerged unit weight of 1 t/m3. The well is subjected to a horizontal force of 50t and bending moment of 400tm at the scour level. Assuming the well acts as a lightweight retaining wall, the allowable total equivalent resting force due to earth pressure with a safety factor of 2 is calculated.
A group of 16 square piles extends 12 m into stiff clay soil, underlain by rock at 24 m depth. Pile dimensions are 0.3 m x 0.3 m. Undrained shear strength of clay increases linearly from 50 kPa at surface to 150 kPa at rock. Factor of safety for group capacity is 2.5. Determine group capacity and individual pile capacity.
The group capacity is calculated to be 1600 kN. The individual pile capacity is determined to be 100 kN. The factor of safety of 2.5 is then applied to determine the safe load capacity.
- There are four main methods to measure the load carrying capacity of piles: static methods, dynamic formulas, in-situ penetration tests, and pile load tests.
- The ultimate load capacity (Qu) of an individual pile or pile group equals the sum of the point resistance (Qp) at the pile tip and the shaft resistance (Qs) developed along the pile shaft through friction between the soil and pile.
- Meyerhof's method is commonly used to calculate Qp in sand based on the effective vertical pressure at the pile tip multiplied by the bearing capacity factor Nq.
Lecture 11 Shear Strength of Soil CE240Wajahat Ullah
Shear Strength of Soil
Shear strength in soils
Introduction
Definitions
Mohr-Coulomb criterion
Introduction
Lab tests for getting the shear strength
Direct shear test
Introduction
Procedure & calculation
Critical void ratio
This document discusses lateral earth pressure and provides details on Rankine's theory and graphical methods for determining active and passive earth pressures. It explains that lateral earth pressure is exerted by soil on retaining structures and depends on whether the structure is stationary or moving towards/away from the soil mass. Rankine's theory assumes dry, homogeneous soil and a vertical wall. Rebhann and Culmann's graphical methods can be used to locate the failure plane and determine the magnitude and direction of lateral earth pressures based on the soil's friction angle and the structure's orientation.
This document discusses settlement of structures. It defines settlement as the vertical downward movement of a structure resulting from deformation of the supporting soil. Settlement includes three components: immediate/elastic settlement occurring within 7 days; primary consolidation settlement over time as pore water is expelled from saturated soils; and secondary compression of the soil skeleton. Differential settlement occurs when different parts of a structure settle by different amounts, potentially causing tilting. Common causes of settlement include excessive structural loads, weak soil compaction, changing groundwater levels, transpiration by plants, earthquakes, and drainage issues. Foundations must be designed to support dead loads, live loads, wind loads, and seismic loads without exceeding the soil's safe bearing capacity.
This document provides 10 examples of problems related to bearing capacity of foundations. The examples calculate bearing capacity using Terzaghi's analysis for different soil and foundation conditions, including cohesionless and cohesive soils, square and strip footings, and considering the water table depth. One example compares results to field plate load tests. The solutions show calculations for determining soil shear strength parameters, factor of safety, and safe bearing capacity.
This document summarizes bearing capacity theory for shallow foundations. It defines key terms like ultimate, net ultimate, and safe bearing capacities. It describes Terzaghi's bearing capacity equation, which considers soil shear strength parameters (c, φ), surcharge loads, and bearing capacity factors (Nc, Nq, Nr). It outlines the failure geometry Terzaghi assumed, with five distinct failure zones. It also distinguishes between general shear, local shear, and punching shear failures based on soil properties and characteristics. Empirical modifications are suggested for local shear failures. Charts summarize the bearing capacity equations for different shaped footings based on experimental results.
This document discusses preconsolidation pressure in soils. It defines preconsolidation pressure as the maximum effective vertical overburden stress a soil sample has experienced in the past. Though it cannot be directly measured, it can be estimated using methods like analyzing the curvature of a consolidation curve. A soil is considered normally consolidated if the current vertical effective stress is equal to or greater than the preconsolidation pressure. The document also lists factors that can cause a soil to approach its preconsolidation pressure, such as changes in total stress, pore water pressure, soil structure, or environmental conditions. Finally, it states that knowing the preconsolidation pressure is important for predicting settlement, site preparation for construction, and determining appropriate
This presentation includes Definition of Permeability, measurement of Permeability, Validity of Darcy's law, Darcy's Law, Methods of Finding Permeability, factors affecting permeability, Permeability of Stratified Soil
FIELD TEST FOR BEARING CAPACITY-revised for BC.pptxsbarai0802
This document discusses various field tests used to determine bearing capacity of soils, including the standard penetration test (SPT), plate load test, cone penetration test (CPT), and pressure meter test. The SPT involves driving a split spoon sampler into the ground using a hammer and measuring the blow counts, while corrections are applied to the observed value. The plate load test applies incremental loads to a steel plate in a pit until a maximum settlement is reached to determine ultimate bearing capacity. The CPT provides continuous measurements of cone resistance with depth to assess soil properties. The pressure meter test measures volume changes in a probe under increasing gas pressure to identify elastic and plastic soil behavior.
1) The document provides notes on soil mechanics topics written by Saqib Imran, a civil engineering student in Peshawar, Pakistan.
2) It includes definitions of soil mechanics, descriptions of soil testing methods like the unconfined compression test, and explanations of soil mechanics concepts like active earth pressure on retaining walls.
3) The notes are intended to help other students and engineers working in the field to gain knowledge on soil mechanics subjects. Saqib provides his contact information for anyone with questions.
The document discusses various field and laboratory testing methods for geotechnical investigations. It describes common in-situ tests like the Standard Penetration Test (SPT), Cone Penetration Test (CPT), Dynamic Cone Penetration Test (DCPT), Vane Shear Test (VST), Dilatometer Test (DMT), and Pressuremeter Test (PMT). It also discusses procedures, components, interpretations and limitations of these tests. The document then briefly covers rock testing methods like Unconfined Compression Test, Brazilian Test, Point Load Test, and Schmidt Rebound Hardness Test.
Analysis and design of embedded pipes: pipelines, vertical hollow piles.Soil-structure reactions for applied displacements of horizontally embedded systems at serviceability and ultimate limit states.
The design of a Buried Steel Pipeline with straight pressure under a road, within a ditch trench. Checking the ULS & SLS conditions both in the plane of the pipeline section & in the vertical plane along pipeline axis.
This document summarizes in-situ methods for determining soil properties, specifically the vane shear test and pressure meter tests.
The vane shear test directly measures the undrained shear strength of soft clays in the field by inserting a rotating vane and measuring the torque. Pressure meter tests measure the soil's stress-strain response by expanding a membrane probe against the soil and recording the resulting pressures and strains. Self-boring pressure meters can test undisturbed soil by drilling into the ground, while displacement pressure meters push into pre-drilled boreholes. Both provide fundamental soil properties with minimal empirical corrections needed.
1. Foundation settlement includes immediate, primary consolidation, and secondary consolidation settlements. Immediate settlement occurs after construction, primary consolidation is due to pore pressure dissipation and water expulsion, and secondary consolidation is long-term rearrangement of soil particles under constant effective stress.
2. Vertical stress distribution in soil must be determined to calculate settlement. Several methods are described to calculate stress, including Boussinesq analysis and Westergaard's method. Simplified methods and charts like Newmark's can also be used.
3. Settlement is calculated using soil properties like compression index, preconsolidation pressure, and void ratio. Methods are described for cohesive and cohesionless soils using parameters from tests like
This experiment aims to determine the undrained shear strength of remolded cohesive soil using a vane shear test. The vane shear test involves pushing a four-bladed vane into a soil sample and rotating it until shear failure occurs along a cylindrical surface. The torque required to cause failure is measured and converted to a unit shear resistance. This test is suitable for soft soils where other shear tests may not work accurately, and it can be used to find both the undisturbed and remolded shear strengths to estimate soil sensitivity. The procedure involves filling a container with soil at a set density and water content, inserting the vane, and rotating it until failure while recording the applied torque and calculated shear strength.
This document outlines procedures for performing an unconfined compression test to determine the shear strength of cohesive soils. It describes the objectives of the test as measuring the shearing resistance and shear strength parameters (c and φ) of undisturbed or remolded cohesive soil specimens. The theory section explains that the unconfined compressive strength is the load per unit area at which a soil cylinder fails in compression and is used to calculate the soil's undrained shear strength as one half the unconfined compressive strength. The document provides details on required equipment, procedures for specimen preparation and testing, methods for data analysis and calculation of stress and strain, and conclusions regarding determination of unconfined compressive strength and undrained
The document discusses different methods for determining the shear strength of soils, including direct shear tests, triaxial shear tests, and unconfined compression tests. Direct shear tests apply a normal stress and increase the shear stress until failure to determine the soil's cohesion (c) and angle of internal friction (φ). Triaxial tests confine a soil sample and then apply additional stress to determine c and φ under drained or undrained conditions. Unconfined compression tests determine c for cohesive soils by compressing an unconfined sample.
The document discusses different types of triaxial tests used to determine the shear strength parameters of soils, including consolidated drained (CD), consolidated undrained (CU), and unconsolidated undrained (UU) tests. It focuses on the UU test, explaining the test procedure, data analysis, and determination of shear strength parameters. Key points include the use of Skempton's pore water pressure parameters B and A, the effect of saturation and drainage conditions, and practical applications of UU analysis such as modeling embankment and footing construction on soft clays.
This document discusses different types of triaxial tests used to determine shear strength parameters of soils, including consolidated drained (CD), consolidated undrained (CU), and unconsolidated undrained (UU) tests. It provides details on conducting UU triaxial tests, including applying cell pressure and deviator stress, and measuring resulting pore water pressure changes. UU tests are useful for modeling short-term undrained loading conditions in the field, such as rapid embankment construction. Both drained and undrained conditions depend on soil type, loading rate, and other factors. While undrained strength is not a fundamental property, it can be used to analyze total stresses under undrained loading.
The document discusses soil strength and different methods for measuring it. The Mohr-Coulomb failure criterion describes soil strength in terms of effective stresses. Laboratory tests like shear box and triaxial tests are used to measure soil strength parameters. The triaxial test can measure both drained (effective) and undrained strengths under controlled stress conditions. Interpretation of test results requires using concepts like effective and total stress Mohr circles.
The document summarizes the standard penetration test (SPT), a common in situ geotechnical testing method. It describes the basic procedure, which involves driving a split spoon sampler into subsurface soils using a hammer, and recording the number of blows required for each increment of penetration. Corrections are made to SPT values to account for overburden pressure and dilatancy. Empirical correlations are presented relating SPT values to properties like density, shear strength, and consistency of cohesionless and cohesive soils. Both advantages like being inexpensive and quick, and limitations like lack of precision are discussed.
This document provides procedures for conducting normal consistency, set time, compressive strength, tensile strength, and flexural strength tests on cement paste and mortar samples. It defines key terms and outlines the steps to prepare and test samples using a Vicat apparatus and universal testing machine. The results from 7-day compressive strength tests on cement mortar cubes met the ASTM C52 specification of 83.6 psi. Running additional tests at 1, 3, and 28 days would have shown how strength increases over time.
1) The experiment determines the unconfined compressive strength (qu) of soil, which is the maximum load per unit area at which an unconfined cylindrical soil specimen fails during compression testing.
2) A cylindrical soil specimen is prepared at optimum moisture content and maximum dry density, and compressed axially between loading plates at a controlled strain rate while measuring load and deformation.
3) The stress-strain curve is plotted, and qu is taken as either the peak stress or stress at 20% axial strain. Shear strength S of the soil is then calculated as qu/2, assuming the soil's angle of shearing resistance φ is 0.
This document provides an overview and summary of key concepts from a PE refresher course on geotechnical engineering. It covers soil classification methods including the USCS and AASHTO systems. It also discusses important soil properties like grain size, plasticity, compaction, permeability, consolidation, and shear strength. Applications covered include settlement analysis, slope stability, shallow and deep foundations, and retaining structures. Calculation of stresses, settlements, and determining appropriate soil parameters for analysis are also summarized.
The document discusses shear strength of soils and describes the triaxial shear test. It explains that the triaxial test subjects a soil specimen to three compressive stresses in perpendicular directions to measure its mechanical properties. Direct shear and triaxial tests are described and compared. The triaxial test apparatus and procedures for unconsolidated-undrained, consolidated-undrained, and consolidated-drained triaxial tests are outlined. Advancements in triaxial testing options and conclusions on benefits of the triaxial test are presented.
For full course visit our website :
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This test (IS: 2131 – 1981) is performed in a clean hole, 100 to 150 mm in diameter.
A casing or drilling mud is used to support the sides of the hole.
This test is most commonly used for cohesionless soil which can not be easily sampled.
Useful for determining the relative density and the angle of shear resistance.
It can also be used to determine the unconfined compressive strength of cohesive soil.
The test shall be made,…
At every change in stratum
At intervals not more than 1.5 m
If the number of blows for 150mm exceeds 50 it is taken as a refusal and the test is discontinuous
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The Standard Penetration Test (SPT) involves driving a thick-walled sampler into the ground using blows from a hammer. The number of blows required for each 150mm of penetration is recorded. Higher blow counts indicate denser soil. SPT results provide an indication of soil strength properties and relative density, especially in granular soils where undisturbed samples are difficult to obtain. However, SPT results have limitations as the test can disturb soils and the blow count data has low resolution. Correlations are used to interpret SPT results but depend on soil type.
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2. Introduction:-
Unconfined Compression Test is a special type of Unconsolidated –
Undrained (UU) test that is commonly used for clay specimens. It is special
case of a triaxial compression test.
In this test the confining pressure (𝜎3) is 0. In this, cylindrical soil
specimen (with height to diameter ratio of 2 to 2.5) is loaded axially by a
compressive force until failure takes place. No rubber membrane is
necessary to encase the specimen. The vertical compressive stress is the
major principal stress (𝜎1) and the other two principal stresses are zero.
This test may be conducted on undisturbed or remoulded cohesive
soils. It cannot be conducted on coarse-grained soils such as sands and
gravels as these cannot stand without lateral support. Also the test is
essentially a quick or Undrained one because it is assumed that there is no
loss of moisture during the test, which is performed fairly fast.
3. Required apparatus for Unconfined compression test:-
o Compression Machine
o Proving Ring of capacity 500 N & 1000 N ( with least count 1.0 & 0.2 resp.)
o Dial gauge of least count of 0.01 mm.
o Split mould of internal dia. 38 mm & length 76mm.
o Sampling tube of internal dia. 38mm & length 200mm.
o Balance of accuracy 0.1 gm.
o Sample extractor
o Stop watch
o Scale
o Knife
o Grease / oil
5. The main question is how to perform unconfined compression test ????
Procedure:-
→ Push the sampling tube into the sample, remove the sampling tube
along with the soil.
→ Saturated the soil sample in sampling tube.
→ Coat the inside of the split mould with a thin layer of grease/oil to
prevent adhesion of the soil.
→ Extrude the specimen from the sampling tube to the split mould with
the help of sample extractor and knife.
→ Trim the two ends of the mould.
→ Weight the soil sample and mould.
→ Remove the sample from the mould by spliting it in two parts.
→ Measure the length and dia. of the specimen.
→ Place the specimen on the bottom plate of the compression machine.
→ Raise the bottom plate of the machine to make contact of the
specimen with the upper plate.
6. → Adjust the strain dial gauge and proving ring dial gauge to read zero.
→ Apply the compression load by raising the bottom plate of the machine to
produce axial strain at a rate of
1
2
to 2% per minute.
→ Record the strain and proving ring dial gauges readings every 30 seconds.
→ Compress the specimen till it fails or 20% vertical deformation is reached,
whichever is earlier.
→ Note the least count of strain gauge and load dial gauge.
7. From the recorded value of strain and proving ring dial gauge reading(after
every 30 sec. interval, before failure), we will draw a stress stain curve
8. Due to this test we can check the various parameters of the soil, like
• Unconfined compressive strength
• Sensitivity of soil
• Shear parameters of the soil, etc.
The Unconfined Compressive Strength (qu) is defined as the ratio of
failure load to the cross sectional area of the soil sample, if it is not
subjected to any lateral pressure.
Where:-
𝑞 𝑢 = Unconfined Compressive Strength
P = Failure Load
AC = Corrected Area at failure.
𝑞 𝑢 =
𝑃
𝐴 𝑐
9. Ac =
Ao
1−e
Ao = Initial Area
e = Strain
Again, ∆𝐿 = Change in length
𝐿 𝑂 = Initial Length of the sample
Water content of the soil is assumed to remain constant during
the duration of the test which generally takes only a few minutes.
e =
∆L
LO
qu, kN/m2 Consistency
<25 Very soft
25-50 Soft
50-100 Medium
100-200 Stiff
200-400 Very stiff
>400 Hard
Relationship between consistency of clays and qu
10. Sensitivity (St), is defined is the ratio unconfined compressive strength of
undisturbed soil sample to the unconfined compressive strength of
remoulded soil sample at constant moisture content.
Sensitivity =
Unconfined compressive strength of Undisturbed soil sample
Unconfined compressive strength of Remoulded soil sample
Soil classification on the basis of sensitivity
Sensitivity St
Nature of clay
1 Insensitive clays
1-2 Low-sensitive clays
2-4 Medium sensitive clays
4-8 Sensitive clays
8-16 Extra-sensitive clays
>16 Quick clays
11. Cohesion of the soil sample may be calculated by using the following
relations
Where:- 𝜎1 = Major principal stress at failure
𝜎3 = Minor principal stress at failure
α = Failure angle with major principal plane
𝜎1 = 𝜎3 𝑡𝑎𝑛2 𝛼 + 2C 𝑡𝑎𝑛. 𝛼
𝛼 = 45 +
∅
2
Where:- ∅ = Angle of internal friction
In unconfined compression test, 𝜎3 = 0
𝜎1 = qu
12. Hence,
∴
If the soil sample is fully saturated and no drainage is allowed, then ∅ = 0,
∴
qu = 2C tan (45 +
∅
2
)
C =
𝑞 𝑢
2 𝑡𝑎𝑛(45+
∅
2
)
C =
qu
2
Shear Strength of the soil is estimated from coulomb's equation :
Where:- 𝜏𝑓 = Shear strength
𝜎 𝑒𝑓 = Effective normal stress
If ∅ = 0, then
𝜏𝑓 = C + 𝜎 𝑒𝑓 tan ∅
𝜏𝑓 = C
13. The Mohr circle can be draw for stress conditions at
failure. As the minor principal stress is zero, the Mohr circle passes through
the origin .The failure envelop is horizontal. The cohesion intercept is equal to
the radius of the circle.
Mohr Circle for Unconfined Compression Test
14. VISUAL VIEW OF UNCONFINED COMPRESSIVE STRENGTH OF COHESIVE SOIL
15. Problems:-
In an unconfined compression test, a sample of sandy clay 8 cm long and 4 cm in
diameter fails under a load of 120 N. Compute the cohesion & shearing resistance
taking into account the effect of change in cross-section of the sample.
a) Sample fail at 10% strain
b) Sample fail at 30% strain, Also draw the Mohr circle.
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