Long-term settlement behaviour of metro tunnels in the soft deposits of Shanghai

Experimental study on performance of geosynthetic-reinforced soil model walls on rigid foundations subjected to static footing loading

Scour is a process of soil erosion, which can occur around the foundations of bridges or offshore structures through the action of flowing water; it can, therefore, reduce the capacity of the foundations and sometimes lead to the failure of structures. During an analysis of scour effects on laterally loaded piles, scour hole geometry is often ignored. Instead, scour effects are considered by simply removing the whole soil layer to the scour depth. However, a scour hole has not only depth, but also width and a slope. At present, the widely used p-y method for analyzing laterally loaded piles cannot consider three-dimensional scour hole dimensions. For this reason, a simplified method was developed herein for the analysis of laterally loaded piles in sand under a scour condition. The p-y curves in this method were based on a wedge type of failure. The effects of the scour hole dimensions on the response of laterally loaded piles in sand were evaluated using this simplified method. The computed resul...

Analysis of Laterally Loaded Piles in Sand Considering Scour Hole Dimensions

To consider the benefit of geosynthetic reinforcement in a mechanistic-empirical pavement design method, the resilient modulus and permanent deformation behavior of a geosynthetic-reinforced unbound granular material (UGM) must be considered. Many researchers conducted repeated-load triaxial (RLT) tests to investigate the resilient and permanent deformation behavior of the geosynthetic-reinforced UGM. However, these tests are difficult to perform, and the results are often interpreted empirically. Thus, implementation of the research results is limited. In this study, an analytical model was developed to predict the resilient modulus and permanent deformation of the geosynthetic-reinforced UGM in RLT tests. The analytical model is compatible with the resilient modulus and permanent deformation models in the current mechanistic-empirical pavement design guide. Both planar and three-dimensional geosynthetics can be analyzed using this model. RLT test results from two published studies were selected ...

Analytical Model for Resilient Modulus and Permanent Deformation of Geosynthetic-Reinforced Unbound Granular Material

The deformation of a Geosynthetic reinforced soil (GRS) structure is a key factor in designing this type of retaining structures. On the other hand, the feasibility of artificial intelligence techniques in solving geotechnical engineering problems is underlined in literature. This paper is aimed to show the workability of two soft computing techniques in predicting the deformation of GRS structures. For this reason, first a relevant case study was modelled into ABAQUS, a finite element (FE) software. Then, the FE results (GRS deformations) were checked against the recorded deformations of the full-scale test. Subsequently, 166 finite element analyses were performed for dataset construction. Then, two predictive models of GRS deformations were constructed. For intelligent model construction, two artificial neural networks (ANN) were coupled with Gravitational Search Algorithm (GSA) and Particle Swarm Optimization (PSO), respectively. It was found that both GSA-based ANN and PSO-based ANN predictive models work good enough. However, the correlation coefficient (R) of 0.981 as well as the system error of 0.0101 for testing data suggest that the GSA-based ANN predictive model outperforms the PSO-based ANN model with R value of 0.973 and system error of 0.0127. Overall, findings recommend that the proposed models can be implemented in assessing the performance of geosynthetic reinforced soil structures.

An efficient optimal neural network based on gravitational search algorithm in predicting the deformation of geogrid-reinforced soil structures

Refined numerical modeling of a laterally-loaded drilled shaft in an MSE wall

Numerical analysis of a laterally loaded shaft constructed within an MSE wall

Design of laterally loaded cast-in-place shafts that pass through the reinforcement behind a mechanically stabilized earth (MSE) wall often requires isolation of the shafts from the MSE mass and socketing of the shafts into the underlying stable foundation material, such as bedrock. Sizeable cost and time savings could be realized, while maintaining stability if the shaft could be supported by the MSE mass alone with no rock socket. Construction, instrumentation, and testing of multiple 0.9-m-diameter shafts solely supported by the geogrid-reinforced mass behind a 6-m-high MSE block wall were conducted for the Kansas Department of Transportation (KDOT). This paper describes the design, construction, and instrumentation of the wall and shafts and the results from the lateral load tests of three shafts tested together as a group compared with shafts that were tested individually. This testing protocol was adopted to evaluate the shaft group effect and the effect of shaft distance from the back of the wall f...

Laterally Loaded Shaft Group Capacities and Deflections behind an MSE Wall

Mechanically stabilized earth (MSE) walls are an inexpensive and aesthetically attractive means of retaining soil. While the design principles for MSE structures have been accepted for several decades, space restrictions at MSE wall sites have led to new demands on MSE wall structures to support laterally loaded deep foundation elements constructed within the reinforced mass. Current design procedures for such configurations are by necessity based on very conservative design assumptions due to the lack of test data. This report contains estimates of the capacity of concrete columns, commonly referred to as drilled shafts, constructed behind the facing of a mechanically stabilized earth wall within the reinforced mass. This is the first of two reports on this topic and contains design capacity recommendations for 36-in. diameter shafts constructed behind an MSE wall with a height of 20 ft based on full scale field testing. It also contains recommendations for P-Y curve analyses for similar wall-shaft configurations. These recommendations and a discussion of their development were prepared by Dan Brown and Associates and are presented in Appendix B. The second report will contain capacity recommendations for walls and shafts with a range of heights and diameters based on computer models calibrated with the field data reported herein. A 20-ft tall, 140-ft long MSE block wall was built in accordance with AASHTO and Kansas Department of Transportation (KDOT) specifications using the Mesa system developed by Tensar International. The wall supported eight 36-in. diameter vertical shafts constructed at four different distances from the back of the facing to the center of the shaft. These shafts were then loaded toward the wall facing using a displacement control method. The shafts and wall were monitored using multiple methods as each shaft was loaded to failure. Shafts were determined to have substantial lateral capacity, with capacity and width of shaft influence increasing as the distance of the shaft from the wall increased. The wall facing was very effective at concealing large deformations. Cracks appeared at the back of the reinforcement, suggesting that additional capacity may be achieved by lengthening the reinforcement. Recommendations for design lateral shaft capacities based on ultimate shaft load and on allowable deformations are presented in Chapter Five of this report.

Behavior of Laterally Loaded Shafts Constructed Behind the Face of a Mechanically Stabilized Earth Block Wall

Current practice for designing laterally loaded shafts that pass through a mechanically stabilized earth (MSE) wall often involves isolating the shaft from the MSE mass and anchoring the shaft into rock with a rock socket. Sizeable cost and time savings could be realized, along with continued effective performance and reliability, if a method were available to evaluate the lateral load capacity of a shaft supported by the MSE mass alone without a rock socket. The Kansas Department of Transportation assembled a team to develop such design methods: the construction, instrumentation, and loading of multiple 36-in. (0.914-m) diameter shafts supported within the reinforced mass of a 20-ft (6-m) tall MSE block wall designed according to existing FHWA procedures without consideration of lateral loads. The design and construction of the wall and the shafts, which were designed as drilled shafts, and the results from the lateral load tests of four shafts are described. These shafts had lengths equal to the full height of the wall and had spacings from the back of the wall facing to the center of each shaft of one, two, three, and four shaft diameters. Results for both load and displacement of the shafts, the width of shaft influence, and the relative displacements of the shafts and the wall facing during loading are presented, along with design recommendations.

Matthew C. Pierson

Papers

Refined numerical modeling of a laterally-loaded drilled shaft in an MSE wall

Numerical analysis of a laterally loaded shaft constructed within an MSE wall

Laterally Loaded Shaft Group Capacities and Deflections behind an MSE Wall

Behavior of Laterally Loaded Shafts Constructed Behind the Face of a Mechanically Stabilized Earth Block Wall

Capacities and Deflections of Laterally Loaded Shafts Behind Mechanically Stabilized Earth Wall