| Test Information | |
| Year | 2001 |
| Test Location | Taipao, Taiwan |
| Test Type | Large Scale |
| Reference | Huang, A. B., Hsueh, C. K., O’Neill, M. W., Chern, S., and Chen, C. _2001_. “Effects of construction on laterally loaded pile groups.” J. Geotech. Geoenviron. Eng., 127_5_, 385–397. |
| Purpose | Investigation of the construction effect on laterally loaded pile groups. Note: for BORED PILES see Huang et al. (a); for DRIVEN PILES Huang et al. (b). |
| Keywords | p-y curves;pile groups; p-multipliers; group efficiency; lateral loads; construction effects; driven piles |
| Soil Information | |
| Soil Type | Sand |
| Soil Description | The soils within 80 m depth were classified as silty sand or silt, depending on the fines content, with occasional layers of silty clay. Uniform soil conditions at the test site. The ground-water table was located at 1 m below the ground surface. Note: for further information about soil properties see Huang et al. (a): Soil Information's attachments. |
| Soil Classification | SM-ML |
| Type of Soil Investigations | BEFORE PILE INSTALLATION: boreholes, CPT, SCPT, DMT; AFTER PILE INSTALLATION: DMT, CPT |
| Pile Information | |
| Pile Material | Concrete |
| Pile Placement Method | 13 precast concrete driven piles |
| Material Properties | DRIVEN PILES: Length= 34.0 m, concrete compressive strength= 78.5 (precast)-20.6 (infill) MPa; reinforcement yield stress= 1226 (precast)-471 (infill) MPa, intact flexural rigidity= 0.79 GN-m^2. |
| Pile Cross Section | Circular |
| Outside Section | DRIVEN PILES: D= 80 (outside)-56 (inside) cm |
| Test Configuration | |
| Test Configuration | Pile Group |
| Pile Spacing | 3D |
| Group Arrangement | 12 driven piles in Box Arrangement; 1 single pile test |
| Test Columns | 3 |
| Test Rows | 4 |
| Head Boundary Condition | Fixed |
| Loading | |
| Type of Loading | Static One-Way Cyclic |
| Axial Load | N/A |
| Load Application | Axial compression load tests were performed on single piles P3, P4, and P9. Results of the axial load test on P3 was used to define the axial load-displacement curves in the analysis of laterally loaded pile groups. Lateral load test was conducted on single pile P7, by loading the pile against the adjacent pile cap. Load tests on the two pile groups, 6 bored piles in one group and 12 driven piles in another, were performed by pushing the two pile caps away from each other. |
| Test Results | |
| Max Top Displacement | 13 cm (Note: for further information about load-deflection curves and comparisons with bored piles, see Huang et al. (a): Test Results' attachments). |
| Deflection | 0.16 diam |
| Analysis Method | |
| Software Used | LPILE (Reese and Wang 1993); GROUP (Reese and Wang, 1996) |
| Group Efficiency Factor | 0.72-0.89 |
| P-Multipliers (lead, 2nd, 3rd, n-th rows) | 0.89, 0.61, 0.61, 0.66 |
| P-Y Curves Model | Matlock (1970); Robertson et al. (1989) |
| P-Y Curves Derivation | SINGLE PILES: Derivation of pre-post construction p-y curves from DMT data; PILE GROUPS: Derivation of pre-post construction p-y curves from DMT data and GROUP software |
| Conclusions | |
| Comparisons | SINGLE PILES: The resulting analyses did not match the measurements because the initial p-y curves based on preconstruction DMT were apparently not completely appropriate for the site and construction conditions.The DMT preconstruction p-y curves were adjusted by multiplying all the p values by a single pile adjustment factor Pms. GROUP PILES: To account for the group effects and to facilitate matching between the computed and measured pile group deflection-load relations, two modification factors Fm (=costant for piles in a given row, recommended by Reese and Wang, 1996) and Pmga (= factor that takes into account construction effect (a) pre construction, (b) post construction) were introduced into the group-pile p-y curves.For bored piles, Pmgb /Pmga = 1.19, indicating that the installation of the bored pile group softened the soil surrounding the piles. For the driven pile group, Pmgb /Pmga = 0.70, indicating that the effects of the driven pile group installation was to stiffen the soil surrounding the piles. |
| Outcomes | 1. Bored pile group construction appeared to loosen the soil surrounding the piles, whereas the driven pile group construction apparently caused a densifying effect (construction effects were limited to the top 15 m from ground surface, where soil conditions have the greatest effect on the behavior of laterally loaded piles). 2. The lateral soil resistance against piles in a group can be highly dependent on the type of pile installation (driven or bored) and preconstruction soil conditions. 3. Separation of mechanical effects from installation effects is likely to result in more consistent p multipliers. Specific p multipliers Pm for concrete piles are also likely a function of how the nonlinear bending of the piles is modeled, how the axial stiffness is modeled, and how the connectivity between the piles and pile cap is simulated. |
