This Consulting Engineer has been retained to develop, and administer the test program developed herein and to interpret the test results. Five concrete screw piles were installed and tested at various
sites located within Jefferson Parish. The concrete screw piles were load tested in accordance with ASTM D 1143-94 Standard Test Method for Piles Under Static Axial Compressive Load. These tests were conducted by Citywide Testing and Inspection, Inc. an independent testing laboratory. The test pile locations are indicated on Table 4 below, and are as follows:
Table 4-Test Pile Locations and lengths
Pile No.
Location
Length
Soil Type
Report
1
Emerson St., Terrytown, La.
20’
3
PL-00007
2
E. Claiborne Parkway, Westwego, La.
20’
3
PL-00008
3
Vintage & Iowa, Kenner, La.
25’
11
PL-00001
4
Dead End, Harvard Dr., Metairie, La.
20’
11
PL-00006
5
31st & Washington, Kenner, La
30’
11
PL-00005
Soil classifications indicated in the table above were obtained utilizing soil maps from the Soils Survey of Jefferson Parish Louisiana, prepared by the United States Department of Agriculture, Soil Conservation Service. Test piles were loaded in increments of 1 ton, with each increment being held for one-hour, prior to the application of each succeeding increment. The pile was loaded to failure, in accordance with the Jefferson Parish Building Code. Upon failure, the load was released in three equal decrements; each decrease in load being held for ¼ hour before release of each succeeding decrement. The test pile driving records, and load test results are also included in Table 5, the test pile results are summarized below and are as follows:
Table 5-Test Pile Load Results and Allowable Pile Loads (tons)
Test Pile # Length
Yield Load
1/2 Yield Load
Load @ 1/2” Settlement
1/2” Load @ Settlement
Allowable Pile Load
#1 - 20’
9.0 tons
4.50 tons
9.0 tons
4.50 tons
4.50 tons
#2 - 20’
9.0 tons
4.50 tons
8.0 tons
4.00 tons
4.00 tons
#3 - 25’
11.0 tons
5.50 tons
11.0 tons
5.50 tons
5.50 tons
#4 - 20’
9.0 tons
4.50 tons
7.4 tons
3.70 tons
3.70 tons
#5 - 30’
5.0 tons
2.50 tons
5.6 tons
2.80 tons
2.50 tons
The test results indicate, that for a given soil type, a 20’ long concrete screw pile can be expected to provide approximately equal allowable load capacity to that of a Class 5 timber pile of greater (30’)
length. Similarly, a concrete screw pile can be expected to significantly outperform a Class 9 timber pile of greater length. Recommended allowable loads for single screw piles, in various soil types found
within Jefferson Parish, or compiled in the tables following; for soil/pile interactions not specifically tested, values have been extrapolated based upon the test data and comparisons of piles surface area/unit
length. For ease of comparison, these tables present allowable pile capacities in the same format as Tables #1 and #2 found in section 1300 of the Building Code of Jefferson Parish:
Table 7 - Allowable Single Pile Loads, East Bank of Jefferson Parish
Soil Type
Pile Type
Pile Tip
Maximum Pile Capacity w/o Load Test
11
Class 9
30’
2.5 tons
Class 5
30’
3.0 tons
Class 5
35’
4.0 tons
Class 5
40’
5.0 tons
Screw Pile
20’
4.0 tons
Screw Pile
25’
5.5 tons
1, 3, 5, 20
Class 9
30’
3.0 tons
Class 5
30’
4.0 tons
Class 5
35’
5.0 tons
Screw Pile
20’
4.0 tons
13
Class 9
30’
4.0 tons
Class 5
30’
5.5 tons
Screw Pile
25’
5.0 tons
Adapted from Table #1, section 1300, Building Code of Jefferson Parish
