Soil and Rock Anchors for Mobile Homes

A State of the Art Report

by

William D. Kovacs and Felix Y. Yokel

Available anchor hardware is surveyed and evaluated and pull-out capacity data are compared with hypotheses for predicting anchor pull-out capacity based on soil mechanics principles. The evidence suggests that our ability to predict anchor pull-out capacity by soil mechanics principles is inadequate, and that there is a need for the standardization of test procedures and soil classification and for further test data. Suggestions for future research are presented.

Key words: Anchors; mobile home foundations; soil anchors; soil mechanics; wind upset

Cover: Due to the widespread use of
mobile homes, the safety of their con-
struction is a growing problem in the
U.S.

3.3 Review of the Theoretical Aspects of Anchor

Holding Capacity .

14

14

14

3.4 Review of Available Field and Laboratory Test

4.2 Anchors Developed for Military Applications

4.2.1 General . .

4.2.2 Triangular or Arrowhead Ground Anchors

4.2.3 Other Government Studies on Anchor Types

15

16

16

15

21

24

4.4

4.3.7 Tie-Down Systems Other than Soil Anchors

Hardware Available from Telephone and Power Cables

5.

6.

Theoretical Prediction of Anchor Pull-Out Capacity

5.1 Introduction . .

5.2 Definitions of Terms Used in Soil Classification

5.3 Theoretical Prediction of Pull-Out Capacity

45

46

51

51

59

65

69

71

5.3.6 Effects of Cyclic Loading on Pull-Out Capacity.

5.3.7 Effect of the Angle of Pull On Pull-Out

Empirically Based Methods of Predicting Anchor Pull-Out

Capacity

6.1

General

6.2 Correlation of Pull-Out Capacity with In-Situ Tests

6.2.1 Soil and Rock Class Types and In-Situ Tests .

6.2.2 Correlation of STP Measurement with the Shear

Strength of Soils . . .

6.2.3 Correlation of Pull-Out Capacity with Soil Class.

6.3 Use of Local Experience

Available Load Test Data on Soil Anchors

7.1

8.

Load Test Data from Helix Anchor Tests

7.2 Load Test Data from Triangular Shaped Anchors

7.3 Load Test Data from Expanding Plate Anchors

7.4 Load Test Data from Rock Anchors

Table 5.3

Qualitative and Quantitative Measures for Consistency
of Clays [83] .

43

Table 5.4

Degree of Saturation of Sand in Various States [93]. .

44

Table 5.5

Tabulated Values of Ultimate Pull-out Resistance for
Triangular Shaped Anchors [66] .

Table 7.1

Summary of Pull-out Test Data for 4 inch Arrowhead
Anchors [85] .

105

Table 7.2

Table 7.3

Table 7.4

Summary of Percent Strength Increase due to Angular
Pull-out, Depth Change, and Switch from Single to
Double Anchor Installation for 4 inch Arrowhead
Anchors (Sand) [85]

Summary of Percent Strength Increase Due to Angular
Pull-out, Depth Change, and Shift from Single to
Double Anchor Installation for 4 inch Arrowhead
Anchors (Gravel) [85]

Summary of Data on Arrowhead Anchor Installation
Defects [30] .

108

111

114