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Diaphragm and bored pile retaining walls are often used for the construction of basements, metro station boxes and cut-and-cover tunnels in urban areas. While diaphragm and secant pile walls are generally intended (and assumed in analysis) to be effectively impermeable, contiguous piles may allow through-the-wall seepage even when preventative measures have been undertaken. Provided the flow rates can be tolerated or dealt with, through-the-wall seepage should result in a reduction in pore water pressures behind the retaining wall compared with an impermeable construction, giving the potential for reductions in the depth of embedment and wall thickness, and hence cost. However, this potential is rarely realised owing to the difficulty in quantifying with sufficient confidence the hydraulic regime associated with a leaky retaining wall. This paper reports the results of laboratory investigations and numerical analyses carried out to assess the effect of the inter-pile gaps on the pore pressure distribution around a contiguous pile retaining wall. The results show that the pore pressures behind the piles reduce significantly as the pile spacing is increased. Long-term field monitoring confirms that the pore water pressures are much lower than would be expected for an impermeable retaining wall in similar soil. The applicability of a simple expression linking the pile diameter, pile spacing and the effective permeability of an equivalent uniform wall is demonstrated. [ABSTRACT FROM AUTHOR]

The design of deep excavations requires careful consideration of the influence of various soil/structure interaction mechanisms and detailed issues relating to the construction processes and the mechanics of the soil. Finite-element analysis provides a useful design tool for deep excavations, but care needs to be taken to ensure that an appropriate level of detail is included in the model. This paper describes a three-dimensional finite-element analysis of a deep excavation supported by a diaphragm wall, recently constructed in Shanghai. The principal purpose of the study is to investigate the level of detail that is required in the finite-element model to obtain results that provide a realistic representation of the wall and ground movements measured during the construction process. Studies are conducted on ( a) the influence of the soil constitutive model on the quality of the results; ( b) procedures to model the effect of post-cure shrinkage in the concrete floor slabs; ( c) procedures to model the construction joints in the diaphragm wall; ( d) the relative merits of using shell and solid elements to model the diaphragm wall; and ( e) the sensitivity of the analysis to the assumed initial horizontal stresses in the soil. [ABSTRACT FROM AUTHOR]

The design of tunnels and groundwater collection and filtration systems requires evaluation of water pressure on the structures and/or leakage (inflow rate) into the structures. However, a great deal of uncertainty remains concerning the control of pore-water pressure and inflow rate in underwater tunnels, because there are various factors that influence the hydraulic interaction between the structure and the groundwater. In this paper the relationship between pore-water pressure () and inflow rate () is investigated using a theoretical method for laminar and turbulent flow. The relationship is validated by performing simple experimental studies. [ABSTRACT FROM AUTHOR]

This paper examines the axisymmetric interior loading problem for an incompressible isotropic elastic half-space where the linear elastic shear modulus varies with depth. In particular, the non-homogeneity has an exponential variation either over the entire depth of the half-space, or over a finite depth beyond which it is constant. The mathematical formulation of the traction boundary value problem is developed through the application of integral transform techniques, and the numerical results obtained are compared with results derived from a computational procedure involving a finite-element approach. [ABSTRACT FROM AUTHOR]

Prediction of the long-term settlement of clay soils over tunnels requires a knowledge of the permeability of the soil and of the tunnel lining; however, determination of the lining permeability in the field is difficult. An important contributor to this problem is the lack of knowledge concerning the permeability of the grout between the lining and the soil. This paper presents the results of tests to characterise the properties of grout samples from London Underground tunnels, investigating permeability, porosity, microstructure and composition. The tests revealed that the newer grout was impermeable relative to the surrounding clay. However, the older samples showed much greater permeabilities and an altered grout composition, suggesting that degradation had taken place. Exposure to groundwater appeared to have caused carbonation and sulfate reaction. The combination of chemical reaction and leaching of cementitious and degradation products appears to have made these grouts more permeable, so that the grout could act as a drainage path rather than a barrier. This challenges the typical assumption that the grout acts as an impermeable barrier. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the geotechnical background to the measurement of stiffness parameters, such as elasticity and stiffness of soils. The study performed a numerical experiment to assess the importance of different parameters for the displacement of a particular structure. Results show that the non-linear elasticity proved to be an effective basis for determining geotechnical displacements.

An obituary for professor Robert Edward Gibson is presented.

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Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Géotechnique is the property of Thomas Telford Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article examines the functioning of the secondary dyke in the village of Wilnis, the Netherlands. Since more than half of the Netherlands is below the high-water level of the rivers or sea, dykes are built along the rivers and seas to prevent these areas from flooding. The water from the inundated areas is pumped up into canals with water levels sometimes several metres higher than the land. The water in the canals is prevented from flooding the land by canal dykes, which are called secondary dykes.