KNOCK DETECTION ALTERNATIVES FOR PRODUCTION VEHICLES.

A method for the detection of knock using the sparking plug, and a system which allows the basic nature of the signal from the spark plug to be compared directly with that from an accelerometer are described. Results are presented for a range of engine speeds which highlight the problems and benefits of each sensing technique.

KNOCK DETECTION ALTERNATIVES FOR PRODUCTION VEHICLES.

A method for the detection of knock using the sparking plug, and a system which allows the basic nature of the signal from the spark plug to be compared directly with that from an accelerometer are described. Results are presented for a range of engine speeds which highlight the problems and benefits of each sensing technique.

THEORETICAL ROAD DAMAGE DUE TO DYNAMIC TYRE FORCES OF HEAVY VEHICLES. PART 1: DYNAMIC ANALYSIS OF VEHICLES AND ROAD SURFACES.

Theory is presented for simulating the dynamic wheel forces generated by heavy road vehicles and the resulting dynamic response of road surfaces to these loads. Sample calculations are provided and the vehicle simulation is validated with data from full-scale tests. The methods are used in the accompanying paper to simulate the road damage done by a tandem-axle vehicle.

THEORETICAL ROAD DAMAGE DUE TO DYNAMIC TYRE FORCES OF HEAVY VEHICLES. PART 2: SIMULATED DAMAGE CAUSED BY A TANDEM-AXLE VEHICLE.

The literature relating to road surface failure and design is briefly reviewed and the conventional methods for assessing the road damaging effects of dynamic tire forces are examined. A new time domain technique for analyzing dynamic tire forces and four associated road damage criteria are presented. The force criteria are used to examine the road damaging characteristics of a simple tandem-axle vehicle model for a range of speed and road roughness conditions. It is concluded that for the proposed criteria, the theoretical service life of road surfaces that are prone to fatigue failure may be reduced significantly by the dynamic component of wheel forces. The damage done to approximately five per cent of the road surface area during the passage of a theoretical model vehicle at typical highway speeds may be increased by as much as four times.

Investigation of anti-lock braking strategies for heavy goods vehicles

An articulated lorry was instrumented in order to measure its performance in straight-line braking. The trailer was fitted with two interchangeable tandem axle sub-chassis, one with an air suspension and the other with a steel monoleaf four-spring suspension. The brakes were only applied to the trailer axles, which were fitted with anti-lock braking systems (ABS), with the brake torque controlled in response to anticipated locking of the leading axle of the tandem. The vehicle with the air suspension was observed to have significantly better braking performance than the steel suspension, and to generate smaller inter-axle load transfer and smaller vertical dynamic tyre forces. Computer models of the two suspensions were developed, including their brakes and anti-lock systems. The models were found to reproduce most of the important features of the experimental results. It was concluded that the poor braking performance of the steel four-spring suspension was mainly due to interaction between the ABS and inter-axle load transfer effects. The effect of road roughness was investigated and it was found that vehicle stopping distances can increase significantly with increasing road roughness. Two alternative anti-lock braking control strategies were simulated. It was found that independent sensing and actuation of the ABS system on each wheel greatly reduced the difference in stopping distances between the air and steel suspensions. A control strategy based on limiting wheel slip was least susceptible to the effects of road roughness.

New ground rope for 238 ton stern trawlers

The sea bottom of the Wadge and Pedro Banks are covered with hard corals and rocks, which cause frequent damages to the net and sometimes total loss of the gear (Hamuro, 1966). This has been one of the main reasons why trawling had been restricted to a small area of the Wadge Bank until recent years.

A three-dimensional tunnel model for calculation of train-induced ground vibration

The frequency range of interest for ground vibration from underground urban railways is approximately 20 to 100 Hz. For typical soils, the wavelengths of ground vibration in this frequency range are of the order of the spacing of train axles, the tunnel diameter and the distance from the tunnel to nearby building foundations. For accurate modelling, the interactions between these entities therefore have to be taken into account. This paper describes an analytical three-dimensional model for the dynamics of a deep underground railway tunnel of circular cross-section. The tunnel is conceptualised as an infinitely long, thin cylindrical shell surrounded by soil of infinite radial extent. The soil is modelled by means of the wave equations for an elastic continuum. The coupled problem is solved in the frequency domain by Fourier decomposition into ring modes circumferentially and a Fourier transform into the wavenumber domain longitudinally. Numerical results for the tunnel and soil responses due to a normal point load applied to the tunnel invert are presented. The tunnel model is suitable for use in combination with track models to calculate the ground vibration due to excitation by running trains and to evaluate different track configurations. © 2006 Elsevier Ltd. All rights reserved.

Ground vibration generated by trains in underground tunnels

A popular method used to reduce vibration transmitted from underground railways into nearby buildings is floating-slab track, whereby a concrete slab supporting the two rails is mounted on rubber bearings or steel springs to isolate it from the tunnel invert. This paper adds a track model to a previously developed three-dimensional tunnel model in order to assess the effectiveness of floating-slab track. A slab beam coupled to the tunnel in the wavenumber domain, with the slab bearings represented by an elastic layer, is examined first. A second beam representing the two rails together is then coupled to the slab, and axle masses representing a train are added to the rail beam. Power-spectral densities and RMS levels of soil vibration due to random roughness-displacement excitation between the masses and the rail beam are calculated. Analytical techniques are used to minimise the computational requirements of the model. The results demonstrate the inadequacy of simple mass-spring and Winkler-beam models with rigid foundations for the assessment of the vibration-isolation performance of railway track. They suggest that the achievable insertion loss is modest and that floating the track slab may in fact cause increased transmission of vibration under certain conditions. © 2006 Elsevier Ltd. All rights reserved.

Ground improvement methods for liquefaction remediation

Soil liquefaction continues to be a major source of damage to buildings and infrastructure after major earthquake events. Ground improvement methods are widely used at many sites worldwide as a way of mitigating liquefaction damage. The relative success of these ground improvement methods in preventing damage after a liquefaction event and the mechanisms by which they can mitigate liquefaction continue to be areas of active research. In this paper the emphasis is on the use of dynamic centrifuge modelling as a tool to investigate the effectiveness of ground improvement methods in mitigating liquefaction risk. Three different ground improvement methods will be considered. First, the effectiveness of in situ densification as a liquefaction resistance measure will be investigated. It will be shown that the mechanism by which soil densification offers mitigation of the liquefaction risk can be studied at a fundamental level using dynamic centrifuge modelling. Second, the use of drains to relieve excess pore pressures generated during an earthquake event will be considered. It will be shown that current design methods can be further improved by incorporating the understanding obtained from dynamic centrifuge tests. Finally, the use of soil grouting to mitigate liquefaction risk will be investigated. It will be shown that by grouting the foundation soil, the settlement of a building can be reduced following earthquake loading. However, the grouting depth must extend the whole depth of the liquefiable layer to achieve this reduction in settlements.

Karyotypic evolution of the family Sciuridae: inferences from the genome organizations of ground squirrels

Cross- species chromosome painting has made a great contribution to our understanding of the evolution of karyotypes and genome organizations of mammals. Several recent papers of comparative painting between tree and flying squirrels have shed some light

Geotechnical observations of construction OF A large shallow SCL tunnel in soft ground

The Fort Canning Tunnel is the first road tunnel in Singapore to be built using the sprayed concrete lining (SCL) method. The major technical challenge of this was to construct a 15m wide tunnel by mining in soft ground under a shallow overburden of 3m to 9m. This paper describes the geotechnical investigations and monitoring controls for the safe and progressive execution of the works, such as soil investigations, trial forepoling works, surface settlement monitoring, tunnel settlement monitoring, face movement monitoring, and the observational approach to construction. The monitored field data showed the volume loss to range from 0.4% to 2.1%, and the observed surface settlement trough was found to agree well with the theoretical Gaussian trough. Other observations made include substantial surface settlements induced by the stress relief at and ahead of the tunnel face in spite of the forepoling umbrella, and the higher volume losses associated with higher overburden. Tunnel face movements were observed during installation of forepoling. These observations are of interest to engineers planning future SCL tunnels in similar conditions.