Chapter 17 Subsoil Exploration Soil Substructure Interaction Lab

Chapter 17 Subsoil Exploration 연세대학교 지반공학연구실 Soil Substructure Interaction Lab.

Subsoil Exploration ▶ The purpose of subsoil exploration include the following : 1. Determining the nature of soil at the site and its stratification 2. Obtaining disturbed and undisturbed soil samples for visual identification and appropriate laboratory test 3. Determining the depth and nature of bedrock, if and when encountered Soil Substructure Interaction Lab.

Subsoil Exploration 4. Performing some in situ field test, such as permeability tests (Chapter 5), vane shear tests (Chapter 9), and standard penetration tests 5. Observing drainage conditions from and into the site 6. Assessing any special construction problems with respect to the existing structure (s) nearby 7. Determining the position of the water table Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration ▶ A soil exploration program : 1. Compilation of the existing information regarding the structure 2. Collection of existing information for the subsoil condition – Geologic survey maps – County soil survey maps prepared by the U. S. Department of Agriculture and the Soil Conservation Service Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration – Soil manuals published by the state highway department – Existing soil exploration reports prepared for the construction of nearby structure 3. Reconnaissance of the proposed construction site 4. Detailed site investigation Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration TABLE 17. 1 Spacing of Borings Sowers & Sowers (1970) provided a rough estimate of. Min. depth of borings for multistory building Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration ▶ Light steel or narrow concrete buildings (17. 1 a) (17. 1 b) ▶ Heavy steel or wide concrete buildings (17. 2 a) (17. 2 b) Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration ▶ ASCE (1972) recommended the rules of thumb for estimating the boring depths for buildings : 1. 1. Estimate the variation of the net stress increase, , 2. that will result from the construction of the proposed structure with depth. This variation can be estimated by using the principles outlined in Chapter 7. Determine the depth, , at which the value of is equal to 10% of the average load per unit area of the structure. Soil Substructure Interaction Lab.

17. 1 Planning for Soil Exploration 2. Plot the variation of the effective vertical stress, , in the soil layer with depth. Compare this with the net stress increase variation, with depth as determined in step 1. Determine the depth, , at which. , 3. The smaller of the two depths, and , is the approximate minimum depth of the boring Soil Substructure Interaction Lab.

17. 2 Boring Methods ▶ The test boring can be advanced in the field by several methods : • • Use of augers (Fig 17. 1) Rotary drilling Wash boring (Fig 17. 4) Percussion drilling Soil Substructure Interaction Lab.

17. 2 Boring Methods FIGURE 17. 1 Hand augers: (a) Iwan auger; (b) Slip auger Soil Substructure Interaction Lab.

17. 2 Boring Methods TABLE 17. 2 Dimensions of Commonly Used Hollow-Stem Augers Soil Substructure Interaction Lab.

17. 2 Boring Methods FIGURE 17. 2 Drilling with flight augers (courtesy of Danny R. Anderson, El Paso, Texas) Soil Substructure Interaction Lab.

17. 2 Boring Methods FIGURE 17. 3 Schematic diagram of hollow-stem auger with removable plug Soil Substructure Interaction Lab.

17. 2 Boring Methods FIGURE 17. 4 Wash boring Soil Substructure Interaction Lab.

17. 3 Common Sampling Methods ▶ Methods of sample collection : • Sampling by Standard Split Spoon (Fig 17. 5, Fig 17. 6) • Sampling by Thin Wall Tube (Fig 17. 7) • Sampling by Piston Sampler (Fig 17. 8) Soil Substructure Interaction Lab.

17. 3 Common Sampling Methods FIGURE 17. 5 Diagram of standard split-spoon sampler Soil Substructure Interaction Lab.

17. 3 Common Sampling Methods FIGURE 17. 6 Split-spoon sampler, unassembled (courtesy of Soil test, Inc. , Lake Bluff, Illinois) Soil Substructure Interaction Lab.

17. 3 Common Sampling Methods FIGURE 17. 7 Thin wall tube sampler Soil Substructure Interaction Lab.

17. 3 Common Sampling Methods FIGURE 17. 8 Piston sampler: (a) sampler lowered to bottom of borehole; (b) pressure released through hole in piston rod Soil Substructure Interaction Lab.

17. 4 Sample Disturbance ▶ The degree of disturbance of the sample ; area ratio, (17. 3) where outside diameter of the sampler inside diameter of the sampler ▶ A soil sample can generally be considered undisturbed if the area ratio is less than or equal to 10% Soil Substructure Interaction Lab.

17. 4 Sample Disturbance ▶ Standard split-spoon sampler : ▶ Shelby tube sampler : Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ The unconfined compression strength of clay soils can be approximately correlated to the standard penetration number, N TABLE 17. 3 Approximate Correlation of Standard Penetration Number and Consistency Clay Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ For clays of a given geology, a reasonable correlation between can be obtained FIGURE 17. 9 Correlation between and (based on Djoenaidi, 1985) Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ Note that the notation is the atmospheric pressure (in the same unit as ) ▶ Based on data shown in Fig 17. 9, the reported regression (17. 4) Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ Empirical relationships has proposed to convert to a standard effective overburden pressure of (17. 5) where corrected standard penetration number correction factor field standard penetration number Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ Correlation of Liao and Whitman (1986) where (SI unit) (17. 6) (SI unit) (17. 8) effective overburden pressure in ▶ Correlation of Skempton (1986) ▶ Correlation between and Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test Table 17. 4 Approximate Relationship Between Correlated Standard Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test Cubrinovski and Ishihara (1999) (17. 10) ▶ The angle of friction of granular soils, has been correlated to the standard penetration number (Peck, Hanson, and Thornburn) (deg) (17. 11) Soil Substructure Interaction Lab.

17. 5 Correlations for Standard Penetration Test ▶ Kulhawy and Mayne (1990) provided a correlation for versus (17. 12) Example 17. 1 17. 2 Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶ Vane Shear Test (see Chapter 11) ▶ Borehole Pressure Meter Test FIGURE 17. 10 Schematic diagram for pressure meter test Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests FIGURE 17. 11 Relationship between measuring pressure and measuring volume for Menard pressure meter Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶ For the pseudoelastic zone (17. 13) where modulus of elasticity of soil Poisson’s ratio Cell volume corresponding to pressure (that is, the cell pressure corresponding to the beginning of zoneⅡ) Slope of straight-line plot of zoneⅡ (17. 14) Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶ Relationship between the (17. 12) where shear modulus of soil (17. 16) ▶ The at-rest earth pressure coefficient, (17. 17) where, represents the in situ lateral pressure Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶ Cone Penetration Test FIGURE 17. 12 Dutch cone penetrometer with friction sleeve [After American Society of Testing and Materials (1991). Copyright ASTM. Reprinted with permission. ] Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶The relationship between and can be approximated (after Kulhawy and Mayne, 1990) as (17. 18) ▶ Schmertmann (1970) gave a simple correlation for sand as ; (17. 19) Soil Substructure Interaction Lab.

17. 6 Other In Situ Tests ▶ Trofimenkov (1974) gave correlations for modulus in sand & sand ; (for sands) (17. 20) (for clays) (17. 21) Soil Substructure Interaction Lab.

17. 7 Rock Coring ▶ It may be necessary to core rock if bedrock is encountered at a certain depth during drilling. ▶ It is always desirable that coring be done for at least 3 m. Soil Substructure Interaction Lab.

17. 7 Rock Coring FIGURE 17. 13 Rock coring: (a) single-tube core barrel; (b) double-tube core barrel Soil Substructure Interaction Lab.

17. 7 Rock Coring 1. 1. 2. (17. 22) 2. (17. 23) Soil Substructure Interaction Lab.

17. 7 Rock Coring TABLE 17. 5 Details of Core Barrel Designations, Bits, and Core Samples Soil Substructure Interaction Lab.

17. 7 Rock Coring TABLE 17. 6 Qualitative Description of Rocks Based on RQD Soil Substructure Interaction Lab.

17. 8 Soil Exploration Report ▶ Exploration report : 1. Scope of investigation 2. General description of the proposed structure for which the exploration has been conducted 3. Geologic conditions of the site 4. Drainage facilities at the site 5. Details of boring 6. Description of subsoil conditions as determined from the soil and rock samples collected 7. Groundwater table as observed from the boreholes 8. Details of foundation recommendations and alternatives 9. Any anticipated construction problems 10. Limitations of the investigation Soil Substructure Interaction Lab.

17. 8 Soil Exploration Report ▶ Graphic presentation also need to be attached to the soil exploration report ; 1. Site location map 2. Location of borings with respect to the proposed structure 3. Boring logs 4. Laboratory test results 5. Other special presentations Soil Substructure Interaction Lab.

17. 8 Soil Exploration Report FIGURE 17. 14 Typical boring log. Note: SS=split-spoon sample; ST=Shelby tube sample Soil Substructure Interaction Lab.