Reda M. Bakeer

Pullout and shear tests on geogrid reinforced lightweight aggregate

Abstract This paper contains the results of laboratory tests conducted on a lightweight aggregate reinforced with a geogrid. The large-size shear tests included direct simple shear tests on the aggregate, shear tests on the aggregate reinforced with a uniaxial geogrid, and geogrid pullout tests. All tests were performed on air-dried material samples. Each type of test was repeated using three different confining pressures representing different heights of fill. The angle of internal friction (φ) of the lightweight aggregate material and its interface friction angle (δ) with the geogrid were found to be 52° and 48°, respectively. These values represent an efficiency of friction angle mobilization (Eφ) of about 87%. Some crushing occurred in the material under a higher confining pressure specifically near the front edge and center of the shearbox.

Geotextile friction mobilization during field pullout test

Abstract Small-scale laboratory tests may not yield reliable values for soil–geotextile interface properties due to the effect of scaling. Field tests offer a better alternative to overcome this problem. In situ pullout tests were performed on a full-scale embankment built over a woven polyester geotextile sheet. The field tests were conducted using different fill heights of compacted clayey soil. The performance of the geotextile was examined when the base soil underneath the geotextile was stiff clay of high plasticity or compacted clean river sand. The test section was instrumented to monitor the geotextile movement and the applied pullout force. Results of the tests showed a linear increase in the geotextile frictional resistance with the increase in the fill height. Also, a successive movement response at different locations on the geotextile away from the loaded edge was detected during the early stages of loading. At the slippage load, a continuous rigid body translation occurred in the geotextile sheet without any further increase in the applied pullout force. The suitability of a widely used interface numerical model that consists of a zero-thickness joint element and a nonlinear elastic hyperbolic stress-deformation material model was examined using the finite element technique. The results showed the inadequacy of this model to deal with large deformation problems typically experienced in geosynthetic reinforced soils.

Determination of Time Optimal Diafiltration for an Ultrafiltration Process

An ultrafiltration process (UFP) associated with the Hanford Department of Energy facility separates sodium solution from radioactive solids, which are then individually immobilized. An oversight of the UFP design and operation has identified several areas to improve the capacity of the UFP. This paper presents the development of a time optimal controller for an ultrafiltration process (UFP). The current mode of operation is a form of diafiltration where feed rates into the UFP are matched with the permeate rates (permeate matching diafiltration). Another approach advocated in this paper is to allow the control parameters into the UFP to vary with time and is termed time optimal diafiltration. It will be shown that permeate matching diafiltration and time optimal diafiltration are equivalent in terms of dewatering times, but not in terms of feedback. An empirical model for optimal time was then developed.Copyright

Annular Flow in Lined Pipelines

Lining of a pipe with a polymeric liner is a viable trenchless technology for rehabilitating sewer pipelines. Polymeric liners are typically installed within the deteriorated segments of a sewer line, from one access hole to the next; to essentially create a new pipe within the old pipe without the need for excavation and removal. However, some concerns exist regarding the need to grout or seal the joints where the new liner connects with access holes and laterals. This study attempts to quantify the amount of flow within the annular space that could exist between a polymeric liner and a deteriorated host pipe. Results of full-scale field tests on twelve pipelines lined with four different deformed/reformed or fold-and-form (DR/FF) and cured-in-place-pipe (CIPP) liner products indicated that gaps of different sizes existed in all of the tested pipelines. These gaps resulted in variable annular flow between the liner and host pipe. Based on the results of the full-scale tests, a mathematical relationship was established between the annular flow in a lined pipeline and the annular space. The relationship between the annular flow rate and the average annular gap size depends on the difference in head between the entry and exit points along the pipeline. In turn, the average annular gap size depends on many factors including tolerances and imperfections in the host pipe and liner, conditions of the host pipe and the quality of liner installation. The results of the numerical analysis indicate similar flow rates for annular gap sizes greater than 1.3 mm (50 mils), which suggest tight installations of a liner into the host pipe to eliminate annular flow.

Sliding mode control applied to an ultrafiltration process

A robust controller is developed for an ultrafiltration process (UFP) associated with the Hanford Department of Energy Waste Treatment and Immobilization Plant (WTP). The robust controller is developed from a posed time optimization problem where it is shown in this paper that the developed time optimal controller for the UFP is a form of “Bang, Bang” control that is equivalent to sliding mode control for the resulting first order system. It is further shown that the controlled system is stable with the origin being a globally asymptotically stable equilibrium point of the dynamic system.

G.D.Q.-Expert: An Expert System for Assessing Geotechnical Data Quality Application to the Menard Pressuremeter Test

This paper describes an expert system for assessing the quality of geotechnical tests. Data from any geotechnical test must be analysed and assessed for quality before use in any formal design. This task requires an extensive geotechnical experience and background which makes it ideal for expert system type software. We used an object-oriented methodology associated with production rules for representing knowledge. The system was developed using an object-oriented expert system shell, called Level 5, to run under the Microsoft Windows graphical environment.