Standard Test Methods for Deep Foundation Elements Under Static Lateral Load

Importancia y uso:

5.1 Field tests provide the most reliable relationship between the static lateral load applied to a deep foundation and the resulting lateral movement. Test results may also provide information used to assess the distribution of lateral resistance along the element and the long-term load-deflection behavior. The foundation engineer may evaluate the test results to determine if, after applying the appropriate factors, the element or group of elements has an ultimate lateral capacity and a deflection at service load satisfactory to satisfy specific foundation requirements. When performed as part of a multiple-element test program, the foundation engineer may also use the results to assess the viability of different sizes and types of foundation elements and the variability of the test site.

5.2 The analysis of lateral test results obtained using proper instrumentation helps the foundation engineer characterize the variation of element-soil interaction properties, such as the coefficient of horizontal subgrade reaction, to estimate bending stresses and lateral deflection over the length of the element for use in the structural design of the element.

5.3 If feasible, without exceeding the safe structural load on the element or element cap (hereinafter unless otherwise indicated, “element” and “element group” are interchangeable as appropriate), the maximum load applied should reach a failure load from which the foundation engineer may determine the lateral load capacity of the element. Tests that achieve a failure load may help the designer improve the efficiency of the foundation by reducing the foundation element-length, quantity, or size.

5.4 If deemed impractical to apply lateral test loads to an inclined element, the foundation engineer may elect to use lateral test results from a nearby vertical element to evaluate the lateral capacity of the inclined element.

5.5 The scope of this standard does not include analysis for foundation lateral capacity, but in order to analyze the test data appropriately it is important that information on factors that affect the lateral load-deformation behavior are properly documented. These factors may include, but are not limited to the following:

5.5.1 Subgrade condition and preparation near ground surface.

5.5.2 Height at which lateral load is applied above ground surface.

5.5.3 Changes in pore water pressure in the soil caused by element driving, construction fill, and other construction operations which may influence the test results for frictional support in relatively impervious soils such as clay and silt.

5.5.4 Differences between conditions at time of testing and after final construction such as changes in grade or groundwater level.

5.5.5 Potential loss of soil supporting the test element from such activities as excavation and scour.

5.5.6 Possible differences in the performance of an element in a group or of an element group from that of a single isolated element.

5.5.7 Effect on long-term element performance of factors such as creep, environmental effects on element material, negative friction loads not previously accounted for, and strength losses.

5.5.8 Type of structure to be supported, including sensitivity of structure to deflections and relation between live and dead loads.

5.5.9 Special testing procedures which may be required for the application of certain acceptance criteria or methods of interpretation.

5.5.10 Requirement that non-tested element(s) have essentially identical conditions to those for tested element(s) including, but not limited to, subsurface conditions, element type, length, size and stiffness, and element installation methods and equipment, so that application or extrapolation of the test results to such other elements is valid. For concrete elements, it is sometimes necessary to use higher amounts of reinforcement in the test elements in order to safely conduct the test to the predetermined required test load. In such cases, the foundation engineer shall account for the difference in stiffness between the test elements and the non-tested elements.

Subcomité:

D18.11

Referida por:

D6230-21E01

Volúmen:

04.08

Número ICS:

93.020 (Earth works. Excavations. Foundation construction. Underground works)

Palabras clave:

field testing; jack; lateral static element capacity; load cell; loading procedure; reference beam ;