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DCIP tomografi för kartläggning av jorddjup och strukturer i berg

Olsson, Per-Ivar LU ; Dahlin, Torleif LU ; Johansson, Sara LU ; Rossi, Matteo LU and Ronczka, Mathias LU (2017) Bergmekanikdagen
Abstract (Swedish)
Det finns planer på att bygga ett energilager i berget vid Önneslöv nära Dalby i Skåne. Berggrunden utgörs av en del av Romeleåsen och består huvudsakligen av gnejs med inslag av amfibolit och diabasgångar. Området ligger omedelbart söder om Sydstens stora bergtäkt, där det framgår att berget till stora delar är kraftigt uppsprucket med lervittrade zoner av olika storlek. I samband med byggande genom zoner med sprickor och vittring finns risk för problem med inläckage av vatten och stabilitet. Vidare kan variationer i djup till bergets överyta ge stabilitetsproblem i de övre delarna av en tänkt konstruktion.

Elektrisk resistivitetstomografi (ERT) är en etablerad förundersökningsmetod inför tunnelprojekt, och har använts i stor... (More)
Det finns planer på att bygga ett energilager i berget vid Önneslöv nära Dalby i Skåne. Berggrunden utgörs av en del av Romeleåsen och består huvudsakligen av gnejs med inslag av amfibolit och diabasgångar. Området ligger omedelbart söder om Sydstens stora bergtäkt, där det framgår att berget till stora delar är kraftigt uppsprucket med lervittrade zoner av olika storlek. I samband med byggande genom zoner med sprickor och vittring finns risk för problem med inläckage av vatten och stabilitet. Vidare kan variationer i djup till bergets överyta ge stabilitetsproblem i de övre delarna av en tänkt konstruktion.

Elektrisk resistivitetstomografi (ERT) är en etablerad förundersökningsmetod inför tunnelprojekt, och har använts i stor skala för bland annat Hallandsåstunneln. Metoden ger kontinuerliga modeller av variationer i bergets elektriska egenskaper som kan kopplas till variationer i bergets mekaniska och hydrauliska egenskaper. Då elektrisk resistivitet (DC) kombineras med inducerad polarisation (IP) kallas metoden DCIP-tomografi, vilken kan ge ytterligare information om variationer i materialegenskaper i berget. Med hjälp av nya förbättrade metoder för datainsamling, förprocessering och tolkning är det möjligt att på ett tids- och kostnadseffektivt sätt samla in stora mängder IP-data av god kvalitet, vilket banar väg för bättre och mera nyanserade modeller av berget och variationer i dess egenskaper. Den nyutvecklade tekniken har testats i full skala vid Önneslöv, där tre parallella DCIP sektioner om 1 km med ett maximalt undersökningsdjup på cirka 170 m, plus en 800 m lång korsande sektion har mätts. Vidare har DCIP loggning utförts i två hammarborrhål ned till 200 m djup. I samma borrhål har det även gjorts loggning av diameter, naturlig gammastrålning, seismisk gånghastighet samt flöde under pumpning.

Den geologiska tolkningen av DCIP resultaten stämmer väl överens med vad man kan förvänta sig då man jämför modellerna med dokumentationen av jorddjup samt variation i sprickighet och vittringsgrad från borrningarna. Fördelen med DCIP resultaten är att man får kontinuerliga modeller som kan kopplas till variation i jorddjup, strukturer i berget och hydrogeologiska förutsättningar. De kombinerade undersökningarna med ytbaserade mätningar och borrhålsmätningar kompletterar varandra och ger en säkrare totalbild av variationer i bergförhållandena. (Less)
Abstract
There are plans to build an energy storage in the rock at Önneslöv near Dalby in Skåne. The bedrock is of a part of Romeleåsen and mainly comprises gneiss, with elements of amphibolite and dolerite intrusions. The area is located immediately south of the Sydsten’s large rock quarry, which shows that the rock is mostly heavily fractured with clay weathered zones of different sizes. In connection with underground construction fractured zones and weathering constitutes a risk for problems with water inflow and stability. Furthermore, variations in depth to the upper surface of the rock can lead to stability problems in the upper portions of a planned construction.

Electric resistivity tomography (ERT) is now an established... (More)
There are plans to build an energy storage in the rock at Önneslöv near Dalby in Skåne. The bedrock is of a part of Romeleåsen and mainly comprises gneiss, with elements of amphibolite and dolerite intrusions. The area is located immediately south of the Sydsten’s large rock quarry, which shows that the rock is mostly heavily fractured with clay weathered zones of different sizes. In connection with underground construction fractured zones and weathering constitutes a risk for problems with water inflow and stability. Furthermore, variations in depth to the upper surface of the rock can lead to stability problems in the upper portions of a planned construction.

Electric resistivity tomography (ERT) is now an established pre-investigation method for tunnel projects, and it has been used on a large scale in connection with for example the Hallandsås Tunnel. The method provides continuous models of variations in the electrical properties of the rock in two (2D) and three dimensions (3D) that can be linked to variations in the rock mechanical and hydraulic properties. ERT measured by a combination of DC resistivity and induced polarization can be called DCIP tomography, which can provide additional information about the variation in the material properties of the rock. With the help of new and improved methods of data acquisition, processing and interpretation it is possible to collect large amounts of good quality IP data in a time and cost effective way, paving the way for better and more nuanced models of the rock and variations in its properties. The newly developed technology has been tested in full scale at Önneslöv. Three parallel DCIP sections about 1 km long, with a maximum survey depth of about 170 m were measured, plus a 800 m long cross-section. Furthermore, DCIP logging was carried out in two percussion drill holes down to 200 m depth in which it is furthermore made logging of diameter, natural gamma radiation, seismic velocity and flow rate during pumping.

Geological interpretation of the DCIP results agree well with what one can expect from the documentation of soil depth, and variation in degree of fracturing and weathering as documented from drilling. A major advantage is continuous models that can be linked to variation in soil depth, structures in the rock and hydrogeological conditions. The combined surveys with surface-based measurements and borehole measurements are complementary and provide a more reliable overall picture of the variations in rock conditions. (Less)
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author
organization
alternative title
DCIP tomography for mapping of depth to rock and bedrock structures
publishing date
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Contribution to conference
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published
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keywords
DCIP Teknisk Geologi
conference name
Bergmekanikdagen
language
Swedish
LU publication?
yes
id
3985c356-a341-403d-9cca-2a8ea710ed93
date added to LUP
2017-03-14 10:39:05
date last changed
2017-09-11 11:21:28
@misc{3985c356-a341-403d-9cca-2a8ea710ed93,
  abstract     = {There are plans to build an energy storage in the rock at Önneslöv near Dalby in Skåne. The bedrock is of a part of Romeleåsen and mainly comprises gneiss, with elements of amphibolite and dolerite intrusions. The area is located immediately south of the Sydsten’s large rock quarry, which shows that the rock is mostly heavily fractured with clay weathered zones of different sizes. In connection with underground construction fractured zones and weathering constitutes a risk for problems with water inflow and stability. Furthermore, variations in depth to the upper surface of the rock can lead to stability problems in the upper portions of a planned construction.<br/><br/>Electric resistivity tomography (ERT) is now an established pre-investigation method for tunnel projects, and it has been used on a large scale in connection with for example the Hallandsås Tunnel. The method provides continuous models of variations in the electrical properties of the rock in two (2D) and three dimensions (3D) that can be linked to variations in the rock mechanical and hydraulic properties. ERT measured by a combination of DC resistivity and induced polarization can be called DCIP tomography, which can provide additional information about the variation in the material properties of the rock. With the help of new and improved methods of data acquisition, processing and interpretation it is possible to collect large amounts of good quality IP data in a time and cost effective way, paving the way for better and more nuanced models of the rock and variations in its properties. The newly developed technology has been tested in full scale at Önneslöv. Three parallel DCIP sections about 1 km long, with a maximum survey depth of about 170 m were measured, plus a 800 m long cross-section. Furthermore, DCIP logging was carried out in two percussion drill holes down to 200 m depth in which it is furthermore made logging of diameter, natural gamma radiation, seismic velocity and flow rate during pumping.<br/><br/>Geological interpretation of the DCIP results agree well with what one can expect from the documentation of soil depth, and variation in degree of fracturing and weathering as documented from drilling. A major advantage is continuous models that can be linked to variation in soil depth, structures in the rock and hydrogeological conditions. The combined surveys with surface-based measurements and borehole measurements are complementary and provide a more reliable overall picture of the variations in rock conditions.},
  author       = {Olsson, Per-Ivar and Dahlin, Torleif and Johansson, Sara and Rossi, Matteo and Ronczka, Mathias},
  keyword      = {DCIP Teknisk Geologi},
  language     = {swe},
  month        = {03},
  title        = {DCIP tomografi för kartläggning av jorddjup och strukturer i berg},
  year         = {2017},
}