• Geotechnical Engineering
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• v.13 no.3
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• pp.33-52
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• 1997

A three dimensional nonlinear finite element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with the shell elements, and the soil with solid 3D nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation, and the placement and stressing of the anchors. The numerical model is calibrated against a full scale instrumented tieback wall at the National Geotechnical Experimentation Site (NGES) on the Riverside Campus of Texas A&M University. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior : location of the first anchor, length of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, stiffness of the wood lagging, and of the piles. The implications in design are discussed.

• Geotechnical Engineering
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• v.14 no.6
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• pp.81-92
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• 1998

A beam on elasto-plastic foundation modeling of soldier pile and woodlagging tieback walls or anchored walls was developed and tested. An instrumented full scale tieback wall in sand was constructed at the National Geotechnical Experimentation Bite located on Texas A&M University. The experimental earth pressure deflection relationship (p-y curves) was developed from the measurements. The construction sequence was simulated in the proposed method. The conceptual methodology of an anchored wall design was introduced by using the proposed method. The proposed method was evaluated with the measurements of case histories in sand and clay. A parametric research was performed to study the most influencing factors for the proposed method. It is concluded that the proposed method represents a significant improvement on the prediction of bending moments and deflections of the properly designed walls.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.193-200
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• 1999

An experimental study is described in which a 305-mm-diameter instrumented drilled shaft was installed in a moderately expansive clay soil during the dry season and monitored over a period of about 18 months. The purpose of the study was In investigate the effects of seasonal moisture changes in the soil on the shear stresses imposed on the sides of the drilled shaft and movements of the shaft head. The soil in the vicinity of the test shaft was instrumented to measure suction and ground surface movement and the relation between suction, total stress and shear strength of the soil at the test site was determined through laboratory triaxial compression testing. Daily rainfall and temperatures were also monitored at the test site, the National Geotechnical Experimentation Site at the University of Houston, where control on surface grading and vegetation existed. Over the course of the study induced unit side shear values of up to 54 kPa were measured in the test shaft. A simple computational model was developed that related observed suction changes to unit side shear induced by the expansion of the soil through the use of the laboratory suction-total stress-shear strength relation.

• Geotechnical Engineering
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• v.14 no.5
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• pp.111-128
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• 1998

An experimental study, which included four 305mm-diameter test shafts, one reference shaft with standard design and three test shafts with isolation tubes, is described. The soil was also soil heave and shrinkage that occur during suction changes at the field site. The test shafts were monitored for a period of about 18 months. Maximum ground movements exceeding 35mm were observed. Movements of only 1 to 2mm were observed in the test shafts with isolation tubes, while movements of 4 to 5mm were observed in the reference shaft. A simple computing model was developed to predict, based on suction changes, the maximum amount of ground heave. Relationship among suction. total stress, and volumetric strain was abtained in the laborstory. This relationship, used as inputs to the predictive model, enabled the computation of the maximum ground heave.