Home Courses Articles Watch! Tools Downloads Request ----------------------------------------------------- Soil Mechanics > Physical Properties of Soil > Soil Phase Relationships > Lateral Earth Pressure > At-Rest State > Rankine's Lateral Earth Pressure > Coulomb's Lateral Earth Pressure > Slope Stability > Effects of Water on Slope Stability > Infinite Slope Analysis > Circular Arc Failure of Slope Analysis > Critical Failure Surface Foundation Analysis and Design > Settlement of Shallow Foundations > Settlement types, definitions, and general equation > Immediate settlement computations > Primary Consolidation > Secondary Compression > Bearing Capacity of Shallow Foundations > Terzaghi's Method > Meyerhof's Method > Brinch Hansen's Method > Bearing from SPT Number > Effect of Ground Water Table > Bearing Capacity of Piles (Deep Foundations) > Ultimate Tip Resistance of Piles > Shaft Resistance of Piles > Sheet-pile Walls: Cantilevered and Anchored > Cantilever Sheet Pile Walls Penetrating Sandy Soils > Anchored Sheet Pile Walls Penetrating Sandy Soils > Factors of Safety for Cantilevered Sheet Pile Walls Load Calculation > Structural Loading > Dead Load vs Live Load > Load Combinations Reinforced Concrete Design > General Topics > What Is Concrete? > Concrete Properties > Section Properties of Reinforcing Bars & Cement Types > Load Combinations of Concrete Design > Design of Concrete Members > Reinforced Concrete Beam Design > Flexural Design of Reinforced Concrete Beams > Serviceability of Reinforced Concrete Beams > Shear Design of Reinforced Concrete Beams Structural Steel Design Construction > Elements of construction > Construction Site Layout Planning Elements > All Types of Roofs And Their Details > Types of Foundations From Construction Point of View > All Types of Foundation Materials Timber Design > Design of Timber Members > Design of Sawn Timber Beams or Joists > Design of Sawn Timber Columns and Compressive Members Masonry Design Finite Elements Method > Basics of Finite Elements > Introduction to Finite Elements And the Big Picture > One-dimensional Bars/Springs > Plane Trusses Introduction Concepts & Formulas Videos Solved problems Download Files Bearing from SPT Number Courses > Foundation Analysis and Design > Bearing Capacity of Shallow Foundations > Bearing from SPT Number

Introduction on Bearing from SPT Number :

One of most common methods for determining allowable soil bearing capacity is from standard penetration test (SPT) numbers. It is simply because SPT numbers are readily available from soil boring. The equations that are commonly used were proposed by Meyerhof based on one inch of foundation settlement. Bowles revised Meyerhof’s equations because he believed that Meyerhof’s equation might be conservative.

Concepts and Formulas of Bearing from SPT Number:

Meyerhof’s equations:
For footing width, 4 feet or less:

Qa = (N/4) / K

For footing width, greater than 4 ft:

Qa = (N/6)[(B+1)/B]^{2} / K

Bowles’ equations:
For footing width, 4 feet or less:

Qa = (N/2.5) / K

For footing width, greater than 4 ft:

Qa = (N/4)[(B+1)/B]^{2} / K

Where

Qa: Allowable soil bearing capacity, in kips/ft^{2} .

N: SPT numbers below the footing.

B: Footing width, in feet

K = 1 + 0.33(D/B) £ 1.33

D: Depth from ground level to the bottom of footing, in feet.

Watch! (Videos):
Solved sample problems of Bearing from SPT Number:

Example 1: Determine soil bearing capacity by SPT numbers (English units)
Given

Requirement :

Estimate allowable soil bearing capacity based on.

Solution:

Meryerhof's equation

K = 1+0.33(D/B) = 1+0.33*(2/3) = 1.22

Qa = (N/4) / K = (10 /4) /1.22 = 2 kips/ft^{2}

Bowles’ equation:

Qa = (N/2.5) / K = (10 /2.5) /1.22 = 3.3 kips/ft^{2}

Example 2: Determine soil bearing capacity by SPT numbers (English units)
Given:

Requirement :

Estimate allowable soil bearing capacity based on Meyerhof’s equation.

Solution:

Meyerhof’s equation

K = 1+0.33(D/B) = 1+0.33*(4/8) = 1.17

Qa = (N/6)[(B+1)/B]2 / K = (20/6)[(8+1)/8]2 /1.17 = 3.6 kips/ft^{2}

Bowles’ equation:

Qa = (N/4)[(B+1)/B]2 / K = (20/4)[(8+1)/8]2 /1.17 = 5.4 kips/ft^{2}

Download Files: Read also: Share:

Follow our official Facebook page (@civilengineeringbible) and Twitter page (@CivilEngBible) and do not miss the best civil engineering tools and articles!