Road Engineering

Blasting is a process of breaking the rock mass to excavate the ore and materials. Many open blasting operations are faced with the apparently conflicting requirements of providing large quantities of fragmented rock and of minimizing the amount of damage inflicted upon the surrounding slopes. A slope in strong hard rock is not necessarily stable, nor is a slope in weathered weak rock necessarily unstable. In some cases the reverse is true, depending on the geometry of joints and weak planes. Many slope failures in hard rock occur with no or very little warning. Detection and monitoring may not be feasible, or require sophisticated instruments and procedures that are not practical at some locations. An important element in avoiding catastrophes is to study the site geology for dangerous conditions, implement the types of blasting procedures that minimize failures, and evaluate the potential use of reinforcement or other mechanical stabilizing procedures. Apart from undesired profile of excavation, the conventional blasting damages the surrounding rock mass and structures like buildings, etc. These damages can be minimized by use of controlled blasting technique. The controlled blasting technique (CBT) is used to produce the desired stability of pit walls / slope. The CBT used for slopes is specifically termed as wall controlled blasting technique (WCBT). WCBT includes buffer blasting, trim blasting, line blasting and pre-splitting. Among these, the pre-splitting is the most commonly used technique. This technique has several advantages such as minimum damage from back-break, enhanced carrying capacity, higher structural stability and stable final pit walls or slope at the designed angle thus improving overall safety of wall / slope.

A pre-requisite in slope stability analyses is that the internal structure and the mechanical properties of the soil or rock mass of the slope, are known or can be estimated with a reasonable degree of certainty. Geophysical methods to determine the internal structure of a soil or rock mass may be used for this purpose. Various geophysical methods and their merits for slope stability analyses are discussed. Seismic methods are often the most suitable because the measurements depend on the mechanical properties that are also important in the mechanical calculation of slope stability
analyses. Other geophysical methods, such as electromagnetic, electric resistivity, self-potential, and gravity methods, may be useful to determine the internal structure, but require a correlation of found boundaries with mechanical properties.

Intersections are critical places which experience high levels of accidents due to the availability of vehicle movements from different directions. Therefore, there is a need to understand the factors that significantly contribute to injuries at such places. These factors can fall under different dimensions in traffic safety such as environmental conditions, road user behavior, traffic police enforcement, road design and crash characteristics. The paper will analyze the factors related to crash characteristics and traffic signal operation that affect the likelihood of accident severity located at intersections. The data for intersection accidents in Abu Dhabi from 2013 to 2016 were used in this analysis. Ordinal logistic model was considered for the analysis to account for the ordinal nature of severity levels. Several diagnostics tests of the model were preformed such as parameters evaluation, overall model evaluation and prediction accuracy. For parameter evaluation, out of 11 independent variables, 6 were non-significant and dropped from the model. Most of the non-significant variables were related to the driver-at-fault details. The results of the final model showed an overall good fit based on a p-value of less than 0.05, as well as a good accuracy of prediction 84.8%. Finally, odds ratios were estimated to interpret the final results of the model.

The kinematic test for toppling developed by Goodman and Bray (1976) was based on a two dimensional relationship (90°-δ) +φj <α (where δ= dip of discontinuity, φj, = friction angle of the discontinuity and, α = slope angle). The steeply dipping discontinuities into a slope, which the relationship describes, must have a strike nearly parallel to the strike of the slope. ‘Nearly’ is defined as up to 30° out of alignment though in the original paper by Goodman and Bray the strike had to be within 10°. By using the expressions for toppling failure and substituting instead for δ the apparent dip δa in Hack (1996) it is shown that the zone for toppling can be much larger than the 30° as stated by Goodman (1989). The relationship is derived in terms of principal stresses and apparent dip. The equation is more akin to a phenomena describing limited flexural slip at the surface of the slope resulting in ‘spalling’ of rock fragments from the slope surface. By making a distinction between toppling resulting from ‘over-turning’ and toppling by ‘spalling’ results in the much more limited instability zone on streographic projections as described by Goodman 1989. It is the the spalling that would eventually undermine the layering to form ‘leaning columns’ which can topple by ‘over-turning’ as the term ‘topple’ suggests. The slenderness of the columns and the dip of the layering (‘lean of the columns’) would indicate the likelihood of over-turning.

3D terrestrial laser scanning is nowadays the technique for 3D mapping and documentation of rock faces and tunnels that shows most potential. In this paper two state-of-the-art methods are described to map rock mass fractures on the basis of 3D laser scan data: a semi-automatic method and a fully automated approach. Both methods give good results and have both their advantages and disadvantages in terms of practical implementation. Both methods make use of the very high level of detail and precision that the 3D laser scan data provide. This, together with the rapid method and simple way of data acquisition makes 3D lasers scanning the most promising fracture mapping tool in the future.

Weathering and especially future weathering after construction of a slope is a main cause for failure of a slope during its engineering life-time. In the course of developing a rock mass classification system for slope stability, large quantities of data have been collected for quantification of past and future weathering influences on rock mass geotechnical parameters. This research resulted in the determination of reduction values related to the degrees of rock mass weathering as described by the British Standard, that give the reduction of a geotechnical rock mass parameter if the degree of weathering increases. The large quantity of data allowed for a statistical analysis that assesses the reliability of the values found for the reduction values. These reduction factors are developed in the context of a slope classification system, however, there is no reason that these reduction factors are not valid for other engineering projects in or on rock masses.

Deterioration of rock masses in cut slopes is a main cause for slope failure along road corridors. Deterioration is mainly due to stress relief and weathering. Deterioration rates depend on the properties of the rock mass including its history and the environment in which it is exposed. The rate decreases with time due to formation of a layer of residual material that prevents further contact between fresh mass and weathering agents. This research has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength (IRS) of sandstone in the area around Kota Kinabalu (Sabah, Malaysia), which has a humid tropical climate. The geology in the area consists of interbedded thickly bedded sandstone and thinly laminated shale beds belonging to the Crocker Formation. The research shows that IRS is related to time following a logarithmic function: IRS (t)=105-34 log (1+t). This relationship is likely also valid in other tropical areas and thus can be used for prediction of the intact rock strength development of sandstone over the engineering lifetime of man-made slopes in tropical areas.

The paper presents the impact of the cleaning of a dual carriageway located in a street canyon in Krakow (Southern Poland) on the levels of the PM10 and PM2.5 air concentrations. For this purpose, representative dust samples from the analysed street were collected corresponding to the street cleaning situation, the re-entrained road dust PM10 and PM2.5 emissions were estimated in accordance with the U.S. EPA guidelines, and the particulate matter atmospheric dispersion modelling was carried out using the CALINE4 model for a selected episode of street cleaning. The modelling results were compared with the measurement results of the PM10 and PM2.5 air concentrations obtained from the air quality monitoring station (traffic type) located in the middle of this street canyon. The results of the air dispersion modelling in the canyon zone confirmed the strong impact of street cleaning on the temporary (1-hour) PM10 concentrations in the direct vicinity of the cleaned section depending on meteorological conditions. During the cleaning episode, no significant increase in the PM2.5 concentration in the air was observed.

Three-dimensional (3D) laser scanning data can be used to characterize discontinuous rock masses in an unbiased, rapid, and accurate manner. With 3D laser scanning, it is now possible to measure rock faces whose access is restricted or rock slopes along highways or railway lines where working conditions are hazardous. The proposed method is less expensive than traditional manual survey and analysis methods. Laser scanning  is a relatively new surveying technique that yields a so-called point cloud set of data; every single point represents a point in 3D space of the scanned rock surface. Because the density of the point cloud can be high (on the order of 5 mm to 1 em), it allows for an accurate reconstruction of the original rock surface in the form of a 3D interpolated and meshed surface
using different interpolation techniques. Through geometric analysis of this 3D mesh and plotting of the facet orientations in a polar plot, it is possible to observe clusters that represent different rock mass discontinuity sets. With fuzzy k-means clustering algorithms, individual discontinuity sets can be outlined automatically, and the mean orientations of these
identified sets can be computed. Assuming a Fisher's distribution, the facet outliers can be removed subsequently. Finally, discontinuity set spacings can be calculated as well.

The paper presents the impact of the cleaning of a dual carriageway located in a street canyon in Krakow (Southern Poland) on the levels of the PM10 and PM2.5 air concentrations. For this purpose, representative dust samples from the analysed street were collected corresponding to the street cleaning situation, the re-entrained road dust PM10 and PM2.5 emissions were estimated in accordance with the U.S. EPA guidelines, and the particulate matter atmospheric dispersion modelling was carried out using the CALINE4 model for a selected episode of street cleaning. The modelling results were compared with the measurement results of the PM10 and PM2.5 air concentrations obtained from the air quality monitoring station (traffic type) located in the middle of this street canyon. The results of the air dispersion modelling in the canyon zone confirmed the strong impact of street cleaning on the temporary (1-hour) PM10 concentrations in the direct vicinity of the cleaned section depending on ...

An overview is given of the influence of weathering on engineering structures in and on natural materials. Some recently developed new ideas to incorporate weathering in design are discussed.  All natural materials near and sometimes also deeper below surface of the Earth are subject to weathering.  Notoriously difficult to forecast is the geotechnical behaviour due to future deterioration of the ground mass under influence of weathering. Weathering is a strongly local feature influenced by local circumstances such as local climate and weather, groundwater, and humans. Calculation methods and parameters used in design of engineering structures often do not properly anticipate the degradation of natural materials due to weathering. Preliminary failure, i.e. failure of the engineering structure before the end of the planned lifetime, may be the consequence. Slopes and tunnels start to raffle or may fail completely, and even buried foundations may be affected.

A recent development in the use of lidar remote sensing techniques is ground-based laser scanning. Laser scanning of rock faces yields the spatial relation between all scanned rock surface points, at a very high resolution, basically a dense "point cloud" in three-dimensional space. The subject of this research is to obtain discontinuity information from the point cloud data set, using an approach that can be automated. The first step in this methodology is to interpolate the point cloud data using 3D Delaunay triangulation in order to create a 3D surface. As a 3D triangulated surface, the scanned rock face is represented by a large number of triangles. The orientation of each triangle can subsequently be computed using basic geometrical rules. Analysis of the kernel density stereo plots of the orientation of all triangles, reveal that specific discontinuity sets can be recognised. Obviously, if this approach can be further developed and fully automated, this would give the site engineer or geologist, in real-time, evidence on the internal structure of any discontinuous rock mass. Particularly in areas where access to rock outcrops is poor, application of this technique will be very promising.

ABSTRACT The subsurface is often perceived as a mysterious, perhaps even threatening, realm. But it has always played a key role in fulfilling the needs of societies and in sustaining ecosystems, even though the public is mostly unaware of this. As affordable and sustainable options diminish for a growing, and increasingly urban, population the subsurface may provide challenging solutions to future generations. The focus of this book is the shallow subsurface, i.e. the first 250 metres below the Earth’s surface. This book is aimed at engineers, urban developers, lawyers, policy makers, insurance professionals, geoscientists and others involved with subsurface construction; it provides an overview of technical aspects and also of legal, governmental and policy-making issues. It also aims to raise awareness of assets and threats of the last frontier for human development on the solid Earth, and to shed light on the sustainable use of the subsurface in the past, present and future.

On request of the Department of Geology and Mines of the Kingdom of Bhutan a one-day reconnaissance survey was done of selected stretches along the Thimphu - Phuntsholing Road to assess the slope stability along the road and to assess the opportunities for widening of the existing road. Although the survey was limited in time all stretches have been visited and briefly investigated. The conclusions are that 1) the present slopes and road cuts are instable and dangerous in many places along the road in the investigated stretches, 2) widening the existing road will inevitably require that new very large road cuts have to be made, 3) new large road cuts have to be made by highly skilled engineers and labour and following the most modern techniques in blasting and road cut engineering to ensure that no unnecessary damage (backbreak) is inflicted on the rock mass and future slope faces resulting in unnecessary artificial support requirements, and 4) many new large cuts may require artificial reinforcement by bolts, anchors, etc, to result in stable and safe road cuts. Hence, widening the existing road will be at many locations a major and costly operation. Alternative routings for parts of the road where a wider road can be constructed with less effort and less costs should therefore be considered. It is strongly advised that a detailed engineering geological and geotechnical survey is done in a corridor along the whole road. This to investigate possible alternative routing options for parts of the road, and to obtain rock and soil mass properties in detail. Then a proper evaluation can be made of the efforts and costs of new routed parts of the road compared to widening the existing road.

It is generally accepted that the identification and characterization of discontinuities in discontinuous rock masses is one of the most important aspects in rock mass modelling. Traditional manual field survey methods for gathering discontinuity properties are biased, hazardous, difficult and time-consuming. This paper describes a computer approach, based on terrestrial laser scan data, which seems promising as an alternative survey technique. A terrestrial laser scanner can create rapidly, a highly accurate 3D point cloud models of any outcropping rock mass. The point cloud model can be converted into a virtual 3D surface using digital surface reconstruction. This paper describes a method using clustering algorithms that allow for automated identification and calculation of different discontinuity sets using these virtual rock surfaces. Not only is laser scanning a safer and faster surveying technique, it also provides a more accurate, practice and reliable basis for discontinuity identification and characterization.

Abstract: In this study, 3D terrestrial laser scan data have been used to quantify the surface roughness of rock mass discontinuities, to determine the roughness scale effect and to determine the influence of the range of precision. The Roughness-length method was applied to calculate fractal ...

The formation of mechanical discontinuities (i.e., bedding, joint planes) is one of the main effects of weathering in rock masses. It is also highly important for forecasting the geotechnical properties of a rock mass in the future. The effect is well known in most rock types, but the mechanisms of forming discontinuities and the resulting variation of mechanical discontinuities throughout a rock mass especially in sedimentary rocks such as sandstone in a tropical environment, are often still poorly understood. The aim of this research is to study and understand the discontinuity formation process in a tropical environment. In sandstone in Sabah, Malaysia, discontinuity spacing decreases with higher weathering grades as expected. Three main discontinuity sets are formed and the spacings of the discontinuity sets formed in the thickly bedded sandstone reduced. The discontinuity development is related to weathering processes and governed by predefined, i.e., incipient or internal, planes of weakness that originate during early stages of rock formation and in response to the past and present three-dimensional stress field(s). The paper is motivated by the need to evaluate the engineering implications of mechanical discontinuity sets that are not apparent in rock at lower grades of weathering but that will be formed as a consequence of on-going weathering processes.

Deterioration of rock masses in cut slopes is a main cause for slope failure along road corridors. Deterioration is mainly due to stress relief and weathering. Deterioration rates depend on the properties of the rock mass including its history and the environment in which it is exposed. The rate decreases with time due to formation of a layer of residual material that prevents further contact between fresh mass and weathering agents. This research has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength (IRS) of sandstone in the area around Kota Kinabalu (Sabah, Malaysia), which has a humid tropical climate. The geology in the area consists of interbedded thickly bedded sandstone and thinly laminated shale beds belonging to the Crocker Formation. The research shows that IRS is related to time following a logarithmic function: IRS (t)=105-34 log (1+t). This relationship is likely also valid in other tropical areas and thus can be used for prediction of the intact rock strength development of sandstone over the engineering lifetime of man-made slopes in tropical areas.

After excavation of a road cut, weathering and erosion processes will start acting upon the newly exposed slope material. Field observations show that the resulting degradation caused by stress release, weathering and erosion may have significant effects well before the envisaged end of the engineering lifetime of the road cut. Since 1990 a road cut in Upper Muschelkalk limestone was monitored to study these effects. The classifications and laboratory test results show that degradation of the rock material and rock mass has progressively continued throughout this period, and threatens the stability of the current slope by causing a notable decrease of the bedding plane&#x27;s friction angle. The test results also show the limited usefulness of shear box testing for slope stability assessment. The small size of shear box samples can lead to both a serious over- and underestimate of the in-situ shear resistance.

After excavation of a road cut, weathering and erosion processes will start acting upon the newly exposed slope material. Field observations show that the resulting degradation caused by stress release, weathering and erosion may have significant effects well before the envisaged end of the engineering lifetime of the road cut. Since 1990 a road cut in Upper Muschelkalk limestone was monitored to study these effects. The classifications and laboratory test results show that degradation of the rock material and rock mass has progressively continued throughout this period, and threatens the stability of the current slope by causing a notable decrease of the bedding plane’s friction angle. The test results also show the limited usefulness of shear box testing for slope stability assessment. The small size of shear box samples can lead to both a serious over- and underestimate of the in-situ shear resistance.

Road construction in mountainous areas especially in humid tropical climates is often afflicted
by slope instability. Road cut slopes are designed to be stable over a certain time span; i.e. the
engineering lifetime, however many slopes or parts of slopes fail before the end of the lifetime. The
reasons for failure sometime after construction are likely due to the deterioration of rock masses in
cut slopes. Deterioration is mainly due to stress relief and weathering. Deterioration rates depend on
the properties of rock mass including its history, and the environment in which it is exposed. The rate
decreases with time due to formation of a layer of residual material that prevents further contact
between fresh mass and weathering agents. Stress relief and weathering are often marginally
quantified or simply neglected in slope design (Huisman, 2006), due to lack of understanding and
appreciation of the processes. In addition, the limited quantitative information available makes it
difficult to incorporate the degradation in design. A proper design of a slope for the entire
engineering lifetime of the slope say up to 50 years should include quantitative factors accounting for
the degradation of the rock mass over its lifetime.
This paper presents the result of research that has been done to develop quantitative factors for
incorporation in the design of slopes to account for stress relief and weathering in humid tropical
areas. The quantitative factor was developed by establishing the relationship between weathering
intensity rate and exposure time for the intact rock strength (IRS) of sandstone (SST unit) in the area
around Kota Kinabalu, Sabah, Malaysia. The geology in the area consists of interbedded thickbedded
sandstone and thinly laminated shale beds belonging to the Crocker Formation.