Full scale lateral load testing was performed on four 12.75x0.375 pipe piles spaced at 3.9, 2.9, 2.8, and 1.7 pile diameters behind an MSE wall which was constructed for this research to determine appropriate reduction factors for lateral pile resistance based on pile spacing behind the back face of the wall. The load induced on eight soil reinforcements located at various transverse distances from the pile and at different depths was monitored to determine the relationship between lateral load on the pile and load induced in the reinforcement. Each pile was loaded towards the wall in 0.25 in. increments to a total deflection of 3.0 in. Additionally, wall panel displacement was also monitored to determine if it remained in acceptable bounds. The results of the research indicate that pile resistance tends to decrease as spacing decreases. P-multipliers for the 3.9, 2.9, 2.8, 1.7D tests were found to be 1.0, 1.0, 1.0, and 0.5, respectively using back-analysis with the computer model LPILE. However, these multipliers are higher than expected based on previous testing and research. Piles spaced further than 3.8D can be assumed to have no interaction with the wall. The resistance of piles spaced closer to the wall than 3.8D can be modeled in LPILE using a p-multiplier less than 1.0. The reinforced backfill can be modeled in LPILE using the API Sand (1982) method with a friction angle of 31º and a modulus of approximately 60 pci when a surcharge of 600 psf is applied. If no surcharge is applied, a friction angle of 39º and modulus of 260 pci is more appropriate. Maximum wall panel displacement was highest for the 2.8D test and was 0.35 in. at 3.0 in. of pile head displacement. For all the other tests, the maximum wall displacement at 3.0 in. of pile head displacement was similar and was approximately 0.15 inches. Induced load in the soil reinforcement increases with depth to the 2nd or 3rd layer of reinforcement after which it decreases. Induced load in the reinforcement increases as pile spacing decreases. Induced load in the reinforcement decreases rapidly with increased transverse distance from the pile. Induced load in the reinforcement can be estimated using a regression equation which considers the influence of pile load, pile spacing behind the wall, reinforcement depth or vertical stress, and transverse spacing of the reinforcement.

Installing load bearing piles within the reinforcement zone of mechanically stabilized earth (MSE) retaining walls is common practice in the construction industry. Bridge abutments are often constructed in this manner to adapt to increasing right-of-way constraints, and must be capable of supporting horizontal loads imposed by, traffic, earthquakes, and thermal expansion and contraction. Previous researchers have concluded that lateral pile resistance is reduced when pile are placed next to MSE walls but no design codes have been established to address this issue. Full –scale testing of statically applied lateral loads to four 24”x0.5” pipe piles, and cyclically applied lateral load to four 12.75”x0.375” pipe piles placed 1.5-5.3 pile diameters behind a 20-foot MSE wall was performed. The MSE wall was constructed using 5’x10’ concrete panels and was supported with ribbed strip and welded wire streel reinforcements. The computer software LPILE was used to back-calculate P-multipliers for the 24” piles. P-multipliers are used to indicate the amount of reduction in lateral resistance the piles experience due to their placement near the MSE wall. Previous researchers have proposed that any pile spaced 3.9 pile diameters (D) or more away from the MSE wall will have a P-multiplier of 1; meaning the pile experiences no reduction in lateral resistance due to its proximity to the wall. P-multipliers for piles spaced closer than 3.9D away from the wall decrease linearly as distance from the wall decreases. P-multipliers for the 24” piles spaced 5.1D, 4.1D, 3.0D, and 2.0D were 1, 0.84, 0.55, and 0.44 respectively. Lateral resistance of the 12.75” cyclically loaded piles decreased as the number of loading cycles increased. Lateral resistance of the piles when loads were applied in the direction of the wall was less than the lateral resistance of the piles when loads were applied away from the wall at larger pile head loads. The maximum tensile force experienced by the soil reinforcements generally occurred near the wall side of the pile face when the lateral loads were applied in the direction of the wall. Behind the pile, the tensile force decreased as the distance from the wall increased. Equation 5-4, modified from Rollins (2018) was found to be adequate for predicting the maximum tensile force experienced by the ribbed strip reinforcements during the static loading of the 24” pipe piles, particularly for lower loads. About 65% of the measured forces measured in this study fell within the one standard deviation boundary of the proposed equation.

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Full scale lateral load tests were performed on five piles located at various distances behind MSE walls. Three of the five test piles were production piles used to support bridges, and the other two piles were located behind a MSE wing walls adjacent to the bridge abutment. The objective of the testing was to determine the effect of spacing from the wall on the lateral resistance of the piles and on the force resisted by the MSE reinforcement. Tentative curves have been developed showing p-multiplier vs. normalized spacing behind wall for a length to height ratio of 1.1 and 1.6. The data suggest that with a L/H ratio of 1.6, a p-multiplier of 1 can be used when the normalized distance from the back face of the MSE wall to the center of the pile is at least 3.8 pile diameters. When the L/H ratio decreases to 1.1 a p-multiplier of 1 can be used when the pile is at least 5.2 pile diameters behind the wall. A plot showing the induced load in the reinforcement as a function of distance from the pile has been developed. The data in the plot is normalized to the maximum lateral load and to the spacing from the wall to the pile. The best fit curve is capped at a normalized induced force of approximately 0.15. The data show that the induced force on the reinforcement when a lateral load is applied to the piles decreases exponentially as the normalized distance from the pile increases. The plot is limited to the conditions tested, i.e. for the reinforcement in the upper 6 ft. of the wall with L/H values ranging from 1.1 to 1.6.

ABSTRACTLateral Resistance of Piles near 15 Foot Vertical MSE AbutmentWalls Reinforced with Ribbed Steel StripsJarell Jen Chou HanDepartment of Civil and Environmental Engineering, BYUMaster of ScienceA full scale MSE wall was constructed and piles were driven at various distances behind the wall. Lateral load tests were conducted to determine the effect of pile spacing from the wall on the lateral resistance of the piles and the force resisted by the MSE reinforcement. The piles used for this study were 12.75 inch pipe piles and the reinforcements were ribbed steel strips.Load-deflection curves were developed for piles located behind the wall at 22.4 inches (1.7 pile diameters), 35.4 inches (2.8 pile diameters), 39.4 inches (3.1 pile diameters) and 49.9 inches (3.9 pile diameters). Data results show that the lateral resistance of the pile decreases as the spacing behind the wall decreases. Measured load-deflection curves were used to compare with computed curves from LPILE with p-multiplier developed for the lateral resistance of piles closer to the wall. A curve was created showing the variation of p-multiplier with normalized pile spacing behind the wall. The curve suggests that a p-multiplier of 1 (no reduction in lateral resistance) can be used when a pile is placed at least four pile diameters from the back face of the wall.

Bridges often use pile foundations behind MSE walls to help resist lateral loading from seismic and thermal expansion and contraction loads. Overdesign of pile spacing and sizes occur owing to a lack of design code guidance for piles behind an MSE wall. However, space constraints necessitate the installation of piles near the wall. Full scale lateral load tests were conducted on piles behind an MSE wall. This study involves the testing of four HP12X74 H-piles and four HSS12X12X5/16 square piles. The H-piles were tested with ribbed strip soil reinforcement at a wall height of 15 feet, and the square piles were tested with welded wire reinforcement at a wall height of 20 feet. The H-piles were spaced from the back face of the MSE wall at pile diameters 4.5, 3.2, 2.5, and 2.2. The square piles were spaced at pile diameters 5.7, 4.2, 3.1, and 2.1. Testing was based on a displacement control method where load increments were applied every 0.25 inches up to three inches of pile deflection. It was concluded that piles placed closer than 3.9 pile diameters have a reduction in their lateral resistance. P-multipliers were back-calculated in LPILE from the load-deflection curves obtained from the tests. The p-multipliers were found to be 1.0, 0.85, 0.60, and 0.73 for the H-piles spaced at 4.5, 3.2, 2.5, and 2.2 pile diameters, respectively. The p-multipliers for the square piles were found to be 1.0, 0.77, 0.63, and 0.57 for piles spaced at 5.7, 4.2, 3.1, and 2.1 pile diameters, respectively. An equation was developed to estimate p-multipliers versus pile distance behind the wall. These p-multipliers account for reduced soil resistance, and decrease linearly with distance for piles placed closer than 3.9 pile diameters. Measurements were also taken of the force induced in the soil reinforcement. A statistical analysis was performed to develop an equation that could predict the maximum induced reinforcement load. The main parameters that went into this equation were the lateral pile load, transverse distance from the reinforcement to the pile center normalized by the pile diameter, spacing from the pile center to the wall normalized by the pile diameter, vertical stress, and reinforcement length to height ratio where the height included the equivalent height of the surcharge. The multiple regression equations account for 76% of the variation in observed tensile force for the ribbed strip reinforcement, and 77% of the variation for the welded wire reinforcement. The tensile force was found to increase in the reinforcement as the pile spacing decreased, transverse spacing from the pile decreased, and as the lateral load increased.

Made available in DSpace on 2014-12-17T14:48:16Z (GMT). No. of bitstreams: 1 ArthurGDA_DISSERT.pdf: 3193366 bytes, checksum: 6e05d0803e66a8ae37a24358be586be8 (MD5) Previous issue date: 2013-12-10 / An experimental study has been conducted to investigate the behavior of continuous flight auger (cfa) bored piles and metalic driven H-section piles under lateral loading in cohesionless soils. The piles were tested in two different areas at the same site. Both areas consisted of a 3-m thick compacted superficial fill of pure fine sand, underlain by layers of naturally occurring pure fine-thick sand. Fills are differentiated by the relative densities which were compressed, 45% e 70%, respectively. Each area received one identical pair of cfa piles and two identical pairs of H-piles. A static lateral loading test was performed in each pair of piles. In this work, the pile load test results are reported and interpreted. The horizontal coefficient of subgrade reaction was determined from the results of the loading tests and compared with values determined by correlations based on penetration resistance index of SPT tests (NSPT). p-y formulations describing the static behavior of the piles were applied to the problem under evaluation. Back Analyses were made through theoretical and experimental p-y curves for obtaining input parameters for the analytic models, among which the coefficient of horizontal reaction. The soil pile system horizontal loading at rupture was determined by the theoretical methods and the results were compared with the experimental results, checking its validity / Um estudo experimental foi realizado para investigar o comportamento de estacas escavadas h?lice cont?nua e estacas cravadas met?licas submetidas a carregamentos laterais em areia. As estacas foram ensaiadas em duas ?reas diferentes no mesmo local. Ambas as ?reas eram compostas por um aterro superficial de 3 m de espessura de areia fina, seguido de camadas naturais de areia fina a grossa. Os aterros diferenciam-se pela densidade relativa com que foram compactados, 45% e 70%, respectivamente. Cada ?rea recebeu um par id?ntico de estacas h?lice cont?nua e dois pares id?nticos de estacas met?licas com perfil H . Em cada par de estacas foi executada uma prova de carga est?tica. Neste trabalho, os resultados das provas de carga s?o apresentados e interpretados. O coeficiente de rea??o horizontal do solo foi determinado atrav?s dos resultados das provas de carga e comparado com valores obtidos a partir de correla??es baseadas no ?ndice de resist?ncia ? penetra??o do ensaio SPT (NSPT). Curvas p-y foram constru?das para prever o comportamento de estacas submetidas a carregamentos horizontais. Retro an?lises foram efetuadas atrav?s das curvas p-y te?ricas e experimentais para obten??o de par?metros de entrada para os modelos anal?ticos, dentre os quais o coeficiente de rea??o horizontal. A carga de ruptura do sistema solo estaca foi determinada atrav?s de m?todos te?ricos e os resultados foram comparados com os resultados experimentais, verificando sua validade