Mr. Jay Warren
School of Planning Architecture and Civil Engineering
David Keir Building, Stranmillis Rd., BT9 5AG
1st Class MEng (Hons) Civil Engineering, Queen’s University Belfast
2014 Royal Academy of Engineering: Nuffield Award
2013 ESSO Energy Award
2013 Student Scholarship Award
Structural Behaviour of Concrete Block Pavements: Finite Element Modelling of the Effect of Construction Pattern and Unit Interlock
The maintenance or even replacement of cracked pavements requires considerable financial resources and puts a large burden on the budgets of local councils. In addition to these costs, local councils also face liability claims arising from uneven or cracked pedestrian pavements. These currently cost the Manchester City Council and Preston City Council around £6 million a year each. Design procedures for concrete block pavements are empirical. A considerable amount of research has been directed towards producing design charts relating thickness of base and sub-base material required based on the properties of the subgrade and the traffic characteristics. The design criteria are based on experience and adjusted, if needed, by means of onsite observation and accelerated trafficking tests. However, the accuracy of these methods is limited due to the fact that they are simplified/empirical procedures that ignore certain parameters such as the discontinuous nature of blocks.
A better understanding of the interaction between paving blocks, bedding sand and sub-base is necessary in order to determine the mode of failure of pavements under load. Increasing applied stress may mobilize “rotational interlock”, providing increased pavement stiffness and thus increased load dissipation resulting in lower transmitted stress on the sub-grade. The “rotational interlock” is dependent on the applied stress and this unfortunately is not accounted for in existing mathematical models. It is also dependent on the construction pattern, i.e. basket, stretcher and herringbone, with indications that the paving blocks in herringbone pattern support more load by better interlocking with each other and forming a “flat arch”.
Paving blocks are required to have a compressive strength of 49 N/mm2 and a tensile splitting strength of 3.5 N/mm2. It is the latter that is critical in ensuring good performance of pavements. The high compressive strength of 49 N/mm2 appears to be required for ensuring that the tensile splitting strength of 3.5 N/mm2 is obtained. However, there are also uncertainties as to whether this value of tensile splitting strength is actually needed.
Finite Element Modelling of pavements is needed. However, the complex geometry of concrete block pavements, e.g. discrete and discontinuous units laid in complex paving patterns and connected with jointing sand, still pose problems in achieving accurate predictive modelling of their behaviour under load. Additional complexities for modelling are introduced by the effect of "settling-in" of pavement blocks and their behaviour under cyclic loading. Simplifications are often required to enable finite element modelling and this appears to be discouraging their wider use. Nonetheless, improvement in finite element modelling may assist in understanding the complex mechanism by which stresses are transferred through the pavement layers. Experimental data are needed from fully instrumented segments of pavements laid/constructed in a purpose built laboratory test frame in order to validate such models and subsequently be used for improving the currently available empirical design procedures.
Dr. V. Sivakumar - Dr. M. Soutsos - Prof. J. Chen
Géotechnique – Leading ICE journal on geotechnical research
UNSAT – Conferences on geotechnical research in the field of unsaturated soil mechanics
Graduate Member of the Institution of Civil Engineers
Member of Engineers Without Borders (EWB) UK
3D Modelling (SolidWorks)