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Water in roads: Flow paths and pollutant spread
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering. Koya University. (KTH Land and water resources engineering)ORCID iD: 0003-2017-1969
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For better road construction and maintenance while minimising damage to the environment and groundwater, it is essential to monitor and model hydrological impacts on roads and consider pollution of groundwater. Water content in unbound material in road layers changes continuously and water flow usually occurs along pathways that are the main corridors for pollutant spread to groundwater. Good awareness of hydrological conditions and of water and solute transport in road layers down to the groundwater can be helpful in minimising environmental impacts during construction and operation. Today, road planning is usually carried out without specifically considering hydrological criteria. To improve understanding of the links between water in roads and groundwater, this thesis developed investigation methods and used numerical simulations for estimating seasonal variations, flow pathways and pollutant spread.

Seasonal changes in road water content in an operational road, tracer tests pathways from the road shoulder and percolation down to groundwater were monitored non-destructively using electrical resistivity tomography (ERT). Chloride concentration changes were estimated based on ERT data inversion. New monitoring methodology was assessed and data analysis was performed on ERT data from different road zones and layers, which were analysed statistically and correlated to precipitation, temperature and ground moisture content. Data were collected at a unique road test station on a motorway north-west of Stockholm and in tracer experiments on typical roads in southern and central Sweden. Two-dimensional (2D) models of heat and moisture changes were prepared for a road section, considering vapour pressure and frozen water content changes using partial differential equations (PDE). Model parameters were optimised based on soil moisture and temperature data from the E18 road test station. A PDE model was used for calculating liquid water and ice content changes in different scenarios based on geometry and design changes. Both pathways and travel times were traced by 2D and pseudo 3D inverse modelling of the ERT measurements.

The field data revealed clear preferential pathways of moisture and salt in the road shoulders that varied significantly during different seasons. Most infiltration occurred directly into the road shoulder, but entered the road embankment with higher percolation speed in modern roads than in old roads consisting of natural soils. The simulations showed that seasonal climate changes and the upper boundary condition were key factors determining water content in different road layers. These findings advance understanding of water in roads and represent a step towards more sustainable and environmental friendly road construction and maintenance. In addition the research results give lessons for practice both regarding monitoring and road construction. For monitoring it provides a new method in data collection and analysis. For construction and maintenance, mitigation measures are suggested, which comprise a tight road shoulder, by e.g. adding a fine grained layer on the shoulder or covering with vegetation.

Abstract [sv]

För att kunna bygga långsiktigt hållbara vägar och minimera underhåll och skador på miljö och grundvatten är det viktigt att kunna övervaka och modellera hydrologiska effekter i och på vägen samt risken för påverkan på grundvatten. Vatteninnehållet i de obundna vägskikten förändras över tid och vattenflödet uppträder ofta längs preferentiella flödesvägar vilket kan medföra att föroreningar snabbt kan spridas till grundvattnet. I dag utförs vägbyggnadsplanering vanligen utan att specifikt överväga hydrologiska kriterier. För att förbättra förståelsen av kopplingarna mellan vattenflöde i vägar och grundvatten har denna avhandling utvecklat undersökningsmetoder och använt numeriska simuleringar för att beräkna säsongsvariationer, flödesvägar och föroreningspridning.

Säsongsförändringar i vägvattenhalten i en väg under drift, infiltration i vägrenen och perkolation ner till grundvattnet övervakades icke-destruktivt genom användning av elektrisk resistivitetstomografi (ERT). Kloridkoncentrationsförändringar uppskattades utifrån inverterade ERT-data. En övervakningsmetod med resistivitetsmätningar utvärderades och dataanalys utfördes på ERT-data från olika delar och väglager, vilket analyserades statistiskt och korrelerades med nederbörd, temperatur och markfuktinnehåll. Informationen har insamlats från en unik vägforskningsstation vid en motorväg (E18) nordväst om Stockholm samt i spårämnesförsök på typiska vägar i södra och centrala Sverige. Tvådimensionella (2D) modeller av värme- och fuktförändringar har utvecklats och testats för en vägsektion med hänsyn till ångtryck och vattenhaltsförändringar som beskrivs av partiella differentialekvationer (PDE). Modellparametrarna optimerades baserat på markfuktighet och temperaturdata från vägforskningsstationen. En PDE-modell användes för beräkning av halter av vatten och is i vägstrukturen vid olika scenarier baserat på väggeometri och designändringar av vägens uppbyggnad. Såväl transportvägar för infiltrerande vatten samt transporttiden har utvärderats utifrån 2D och pseudo 3D-invers modellering av ERT-mätningarna.

Fältstudierna visade tydliga preferentiella infiltrations- och flödesvägar för vatten och salt som varierade tydligt mellan olika årstider. Huvuddelen av infiltrationen uppkom i vägens stödremsa och perkolationshastigheten var större på moderna vägar med grovt material i stödremsan jämfört med äldre vägar som huvudsakligen var uppbyggda av omgivande lokalt material. Simuleringarna visade att säsongsmässiga förändringar samt angivna övre gränsförhållanden var viktiga faktorer som kontrollerade vattenhalten i olika väglager. Denna kunskap ger en ökad förståelse för vatten i vägar och kan därför utgöra ett steg mot mer hållbart och miljövänligt vägbyggande och vägunderhåll. Dessutom ger forskningsresultaten ökad kunskap som kan användas praktiskt både vad gäller övervakning och vägbyggande. För övervakning har en ny metod för analys av ERT-data testats. För konstruktion och underhåll föreslås miljöskyddande åtgärder, vilket bland annat omfattar tätning av stödremsan med ett mer finkornigt material eller täckning med vegetation. 

Abstract [ku]

بۆ باشتر بنياتنان و چاككردنەوەى ڕێگاوبان بەبێ ئەوەى ببێتە هۆكار بۆ تێكچونى ژينگە و پىسبوونى ئاوى ژێر زەوى, ئەوا پێوىستە چاودێرى ووردى كاريگەريەكانى شێى ئاو لەسەر چينە پێكهاتەكانى ڕێگا بكرێت لەگەڵ چاودێرى جووڵەى پيسى و قڕێژ (pollutants) كە دەچێت بەرەو ئاوى ژێر زەوى و دەبێتە هۆى پىسبوونى. شێى ئاو لەناو چينە پێكهاتەكانى ڕێگا بە بەردەوامى لە گۆڕاندايە و ڕێگا و شێوەئاساى ناديار دەبڕێت بەناو چینەکانی زەویدا بەرەو ئاوى ژێر زەوى, وە بە هەمان ڕێڕەو پيسى و قڕێژ دەگات بە ئاوى ژێر زەوى  وەدەبێتە هۆكارى پىسبوونى ژينگە. تێگەيشتنى پێويست دەربارەى شێى و جووڵەى ئاو لەناو چينە پێكهاتەكانى ڕێگا سوودبەخش دەبێت لە دروستكردنى ڕێگاوبان بەشێوەيەكى درووست كە ڕێگر بێ لە پىسبوونى ئاوى ژێر زەوى. تا ئەم ساتە لە پرۆسەى دروستكردنى ڕێگاوبان گرينگى ئەوتۆ بەم بوارە نەدراوە. بۆ ئەوەى تيشك بخەينە سەر ئەم بوارە, ئامانجى ئەم توێژينەوەيە بريتيە لە پەرەپێدانى ڕێگاى شيكارى و هاوشێوەسازى ژمارەيى  (numerical simulation) بۆ خەملآندن و زانينى گۆڕانكارييە وەرزييەكانى شێى و جووڵەى ئاو لەناو چينە پێكهاتەكانى ڕێگا و چۆنيەتى گەيشتنى پيسى بە ئاوى ژێر زەوى. 

لەم توێژينەوەيەدا, ڕێگاى وێنەى درووست بوى بەرگرى كارەبايى (ERT) بەكارهێنراوە  بۆ چاودێريكردنى گۆڕانكارييەكان لە چينە پێكهاتەكانى ڕێگايەكى خێرا بێئەوەى ڕێگاكە دەستكارى بكرێت يان ببێتە هۆكار بۆ وەستانى هاتوچۆ. و هەمان ڕێگاى وێنەى درووست بو ى بەرگرى كارەبايى بەكارهێنراوە  بۆ وێنەكێشان و بەدواداچوونى دزە كردنى ئاو لە لێواري  ڕێگاوبان. ڕێژەى خوێى تواوە (خوێى بەكارهاتوو لە زستاندا بۆڕێگرى كردن لە درووست بو نى زقم/ ئاڵشک (frost) لەسەر ڕووى ڕێگاكان) لەناو چينە پێكهاتەكانى ڕێگا خەمڵێنراوە بە بەكارهێنانى هەمان ڕێگاى وێنەى درووست بو ى بەرگرى كارەبايى. شێوازى نوێ بەكارهێنراوە  بۆ كۆكردنەوەى زانيارييەكان (data) و ڕێگە شيكارى تايبەتيش بەكارهێنراوە  بۆ شيكارى ئامارەيى (statistical analysis) ژمارەكانى بەرگرى كارەبايى. ژمارەكان بۆ بەشى جيا جياى ڕێگاكە پۆلێن كراوە و شيكارى ئامارەيى بۆ ئەنجام دراوە تا هاوپەيوەندى (correlation) بۆ بدۆزرێتەوە لەگەڵ تۆمارەکانى كەش و هەوا, باران بارين, پلەى گەرما و ڕێژەى شێى ئاو لە ناو خاك. زۆربەى تۆمارەکان كۆكراونەتەوە لە وێستگەيەكى ناياب بۆ توێژينەوەى ڕێگاوبان لە نێزيك شارى ستۆكهۆڵم. هاوشێوەسازيەكى دوو دوورى (2D simulation model) بۆ خەملآندنى پلەكانى گەرمى و ڕێژەى شێى ئاوى ناو چينە پێكهاتەكانى ڕێگا ئامادەكراوە بۆ بەشێكى ڕێگا و لێواري  ڕێگاكە. لە هاوشێوەسازيەكە ژمێركارى بۆ پاڵەپەستۆى هەڵمى ئاو و گۆڕانكارييەكانى زقم/ ئاڵشک  ئەنجام دراوە. ئەم ژمێركاريانە  بە بەكارهێنانى بەشەهاوكێشەى جياكارى (PDE) جێبەجێ كراوە بۆ گەڵاڵەكردنى هاوكێشەكان و گەيشتن بە ئەنجام. هاوكۆلكەكانى (parameters) دياريكردنى كارى هاوشێوەسازيەكە, هەڵبژاردەى باشترينى (optimization) بۆ ئەنجام دراوە بە پشتبەستن بە داتاى(زانیاری) كۆكراوە لە وێستگەى توێژينەوەى ڕێگاوبان, بەتايبەتى داتاى پلەكانى گەرمى و ڕێژەى شێى.

ئەنجامە كردارەييەكانى(fieldwork results) وێستگەى توێژينەوە بەڕوونى دەريدەخات كە ئاو و خوێى تواوە بەشێكى زۆرى دزە دەكات لە لێواري  ڕێگاكەوە بەرەو ناو چينە پێكهاتەكانى ڕێگاو ئاوى ژێر زەوى. شێوەئاساى بڵاوبونەوەكە (spread pattern) دەگۆڕێت و جياوازە لە وەرزە جياكانى سالدا. خێرايى بڵاوبونەوەكە و شێوەكان چاودێرى كراوە بە هەڵگەڕاندنەوەى ئەنجامەكانى تۆمارى بەرگرى كارەبايى سێ دوورى كە دەريدەخات بڵاوبونەوەكە زۆر خێرايە لە ناو چينە پێكهاتەكانى ڕێگاكە بە بەراوورد لەگەڵ خاكى سروشتى.

لە هاوشێوەسازيەكە مەرجى سنوورى سەرەوە (upper boundary condition) زۆر هەستيارە. بە بەكارهێنانى هاوشێوەسازيەكە توانرا خەملآندن بۆ ڕێژەى شێى ئاو, گۆڕانكارييەكانى زقم/ ئاڵشک و پلەكانى گەرمى چينە پێكهاتەكانى ڕێگاو خاكى ژێرەوەى بكرێت. بە گۆڕينى ئەندازەى ڕێگا, هاوشێوەسازى جياواز ئامادەكرا بۆ زانينى هۆكارەكانى گۆڕانكارى جوڵەى ئاو و گەرمى لەناو چينە پێكهاتەكانى ڕێگا. پابەند بەم توێژينەوانە دەركەوت كە هۆكارە سەرەكيەكانى گۆڕانكارى يەكان بريتين لە گۆڕانكارى كەش و هەوا لە وەرزە جياوازەكاندا. ئەم زانياريانە هەنگاوێك دەمانبات بەرەو باشتر بنياتنان و چاككردنەوەى ڕێگاوبان لەگەڵ پاك ڕاگرتنى ژينگە و ئاوى ژێر زەوى. . يەكێ لە چارەسەرە كردارەييەكان  بۆ كەمكردنەوەى دزە كردنى ئاو لە لێوارى  ڕێگاوبان  بريتيە لە داپۆشينى لێواري  ڕێگا بە خۆڵ و سەوزايى.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 52
Series
TRITA-ABE-DLT ; 188
Keywords [en]
De-icing salt; Road; Tracer test; ERT; Water content; Road pollutants; Flow pathways
National Category
Water Engineering Geophysical Engineering
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-226698ISBN: 978-91-7729-755-0 OAI: oai:DiVA.org:kth-226698DiVA, id: diva2:1201373
Public defence
2018-06-01, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180426

Available from: 2018-04-26 Created: 2018-04-25 Last updated: 2018-04-26Bibliographically approved
List of papers
1. Monitoring of moisture and salinity content in an operational road structure by electrical resistivity tomography.
Open this publication in new window or tab >>Monitoring of moisture and salinity content in an operational road structure by electrical resistivity tomography.
(English)In: Near Surface Geophysics, ISSN 1569-4445, E-ISSN 1873-0604Article in journal (Refereed) Accepted
Abstract [en]

Moisture dynamics in road systems significantly affect road structure design and maintenance. This study analysed moisture dynamics in a cross-section of motorway (the E18) in Sweden during a one-year period through in situ monitoring using electrical resistivity tomography (ERT). The monitoring methodology was assessed since resistivity can provide a good proxy for monitoring moisture in the road structure. Monthly electrical resistivity was calculated by inverting resistivity data along a pre-installed electrical resistivity line beneath the surface asphalt layer of the road at the test site. The electrical resistivity data were then statistically analysed and correlated with local climate data, i.e. precipitation and temperature, and with ground parameters such as moisture content. The results showed high variation in resistivity in the road surface layer and road shoulders depending on weather conditions, water flow and other surface activities. In general, negative correlations between electrical resistivity and precipitation were observed. The results also indicated possible retardation of de-icing salt after accumulating in the top layer during winter. These findings advance understanding of the moisture dynamics in roads and can help improve pavement design in response to future climate change.

Keywords
2D Electrical Resistivity Tomography; Road structures; Moisture content; in-situ monitoring; De-icing salt
National Category
Geophysical Engineering Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-226859 (URN)
Note

 Accepted for publication on 25 January 2018. QC 20180503

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-05-15Bibliographically approved
2. Detecting seasonal flow pathways in road structures using tracer tests and ERT
Open this publication in new window or tab >>Detecting seasonal flow pathways in road structures using tracer tests and ERT
(English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932Article in journal (Other academic) Submitted
Abstract [en]

Roads and traffic can be a source of water-bound pollutants, which can percolate through the unsaturated zone to groundwater. Deicing salt is widely used on roads in northern Europe during winter and is usually applied at a time when the temperature is below zero and the soil is partly frozen. Understanding the mechanism by which water-bound pollutants such as deicing salt are transferred from roads to groundwater is highly important for groundwater protection, environmental sustainability and road maintenance. Electrical resistivity tomography (ERT) can be used for tracing the infiltration of deicing salt in different seasons, including the frozen period, as a step towards identifying pollutant infiltration pathways. In this study, a tracer-ERT monitoring method and analytical process was developed and evaluated for use in investigating and demonstrating deicing salt infiltration pathways in road structures in different seasons and weather conditions. The method involves using dissolved sodium chloride as a tracer and monitoring its infiltration using a multi-electrode array system. The tracer tests were performed at the same location in different seasons over a one-year period.

The results indicated high seasonal variation in percolation pattern and flow velocity, with large decreases in December (winter), most likely due to preferential flow paths within the road shoulder. These findings can be applied to other water-soluble pollutants that move from the road surface to groundwater.

Keywords
ERT, tracer test, flow pathways, road, hydrology
National Category
Geophysical Engineering Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-226860 (URN)
Note

QC 20180503

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-05-15Bibliographically approved
3. Spread of Water-Borne Pollutants at Traffic Accidents on Roads
Open this publication in new window or tab >>Spread of Water-Borne Pollutants at Traffic Accidents on Roads
2017 (English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 228, no 9, article id 323Article in journal (Refereed) Published
Abstract [en]

Traffic accidents sometimes lead to the spread of hazardous compounds to the environment. Accidental spills of hazardous compounds on roads in the vicinity of vulnerable objects such as water supplies pose a serious threat to water quality and have to be assessed. This study compared three different assessment methods, electrical resistivity measurements, analytical flow calculations, and 1D and 2D dynamic flow modeling, to describe rapid transport processes in the road shoulder and roadside verge after a major spill. The infiltration and flow paths of water-borne substances were described during simulated discharge of pollutants on different road types. Full-scale tracer tests using sodium chloride were carried out at nine different road locations in Sweden. Analysis of grain size distribution and infiltrometer tests were carried out at the road shoulder and verges. The pathways and travel times were traced using resistivity measurements and 3D inverse modeling. The resistivity measurements were compared to analytical flow calculations and 1D and 2D dynamic modeling. All measurement sites were highly heterogeneous, which caused preferential flow. Vertical flow velocities of 1.4-8.6 x 10(-4) m/s were measured. The results of the analytical calculations and flow modeling were of the same order of magnitude. The measurements showed that almost all infiltration goes directly into the road embankment, hence the composition and structure of the built-up road must be considered. The non-destructive resistivity measurements and 3D modeling provided useful information for clarifying the infiltration and flow pattern of water-borne compounds from road runoff.

Place, publisher, year, edition, pages
SPRINGER, 2017
Keywords
Road, Pollution, Electrical resistivity, Infiltration, Modeling
National Category
Environmental Sciences Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:kth:diva-215468 (URN)10.1007/s11270-017-3477-3 (DOI)000410827400006 ()28845063 (PubMedID)2-s2.0-85027395214 (Scopus ID)
Note

QC 20171017

Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2018-05-03Bibliographically approved
4. Two-dimensional model for heat and moisture dynamics in Nordic roads: Model set-up and sensitivity analysis
Open this publication in new window or tab >>Two-dimensional model for heat and moisture dynamics in Nordic roads: Model set-up and sensitivity analysis
(English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441Article in journal (Other academic) Submitted
Abstract [en]

Modeling moisture and heat changes in road layers is important for understanding road hydrology, but also for better construction and maintenance of roads. The modeling task is more complicated in cold regions, due to the water-ice phase change in wintertime. This paper presents a two-dimensional model based on a road section. The water and heat transport equations, including freezing/thawing and vapor flow, were implemented within the COMSOL Multiphysics tool. Parameters were optimized from modeling results based on measured soil moisture and temperature at a road test station near Stockholm. Impacts of phase change in the model were assessed. The results showed that model developed can accurately predict temperature changes, water and ice content in different road layers based on pressure head and temperature gradient. The model of water dynamics performs much better than predicting the average water content in the upper road layer. Parameters related to soil water retention curve are optimized and most parameters influence water and heat change in the same direction, except the thermal conductivity of soil. The optimized parameters based on moisture content and temperature data from the sensors in the road section can be used in this model for testing different road materials and geometries. The model provides a clear understanding of water and heat transfer in roads with ideal boundary and initial conditions. For a better understanding of road heat and moisture dynamics, more physical processes can be added to the model in future work by coupling snow melt and surface flow models.

Keywords
Modeling, Road, COMSOL, Heat and moisture, Phase change
National Category
Water Engineering Other Earth and Related Environmental Sciences
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-226861 (URN)
Note

QC 20180503

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-05-15Bibliographically approved

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