| 1. |
- Brantberger, M., et al.
(författare)
-
Controlling grout spreading in tunnel grouting - Analyses and developments of the GIN-method
- 2000
-
Ingår i: Tunnelling and Underground Space Technology. - 0886-7798 .- 1878-4364. ; 15:4, s. 343-352
-
Tidskriftsartikel (refereegranskat)abstract
- In order to choose the best grouting technique, predictions of the grouting result can be made. Due to uncertainties in the predictions, control of the grouting during ongoing work is an important step towards a successful result. One method to control the grouting is the GIN-method developed and presented by Lombardi and Deere (1993). The method focuses on controlling the grout spreading in order to minimise the risk of hydraulic uplift and achieve a more uniform spreading around a bore hole. However, this method is described with emphasis on dam grouting. In this paper, theories are analysed and developed from a tunnel grouting point of view. A concept of a normalised pressure and normalised grout spreading is presented that at the same time enables control of the grout spreading distance as well as the risk of hydraulic uplift. Calculations based on field data are also done in order to visualise and discuss the potential use of developed theories. Some conclusions from the performed analyses are that other mathematical relations than those stipulated by the GIN-method better account for the risk of hydraulic uplift and that higher pressures than the rule of thumb stipulates could be used in good rock. So far, the concept of normalised pressure and normalised grout spreading is in its first stage and is studied mainly from a theoretical point of view. Further studies are thus needed.
|
|
| 2. |
- Cesano, Daniele, et al.
(författare)
-
Parameters regulating groundwater inflows into hard rock tunnels - a statistical study of the Bolmen tunnel in southern Sweden
- 2000
-
Ingår i: Tunnelling and Underground Space Technology. - 0886-7798 .- 1878-4364. ; 15:2, s. 153-165
-
Tidskriftsartikel (refereegranskat)abstract
- Inflow of groundwater into tunnels has always been a major technical and environmental problem for underground constructions. Predictions of groundwater inflow using analytical and numerical tools have often failed due to generalization and simplification of important parameters, especially in heterogeneous media such as crystalline rocks. In order to identify those parameters that regulate inflows, a systematic statistical analysis has been carried out at a tunnel constructed in the hard crystalline rocks of southern Sweden. The parameters included topographically, technically and geologically important variables in the hard crystalline rocks as well as in the overburden. The study revealed that many factors related to the rock quality, as well as to the overburden-such as the number of fractures, the thickness of the overburden, the soil type and the amount of pregrouting-regulated the leakage. It seems that a clear difference exists between the parameters that regulate the major and the minor leakage. The minor leakage is associated more with the drainage of the rock mass, while the major leakage is clearly associated with different parameters in the overburden. Unless the overburden anal the rock mass are considered as an interrelated system, predictions of groundwater inflows are likely to fail.
|
|
| 3. |
|
|
| 4. |
- Eriksson, M., et al.
(författare)
-
Numerical calculations for prediction of grout spread with account for filtration and varying aperture
- 2000
-
Ingår i: Tunnelling and Underground Space Technology. - 0886-7798 .- 1878-4364. ; 15:4, s. 353-364
-
Tidskriftsartikel (refereegranskat)abstract
- Grouting as a mean to reduce the ingress of water to underground facilities has been used for decades. With an increased demand for tightness and cost efficiency, the incentive to improve the method has also increased, and the need to understand the governing factors has been focused. The knowledge concerning grouting involves several fields of research, for instance pow in fractured rock and the behaviour of the grouting material. An understanding of these fields is essential in grouting research. Numerical modelling of grout propagation in fracture geometries is one means of achieving such understanding The paper presents how numerical calculations of grout spread and sealing effect can be used for predictions of the grouting result. The calculation concerns pow of grout in a network of conductive elements, representing a fracture geometry with the scope to understand the governing parameters when grouting. The spread of grout is significantly affected by the spatial variability of the fracture aperture. Measurements on grout properties and laboratory experiments show that the grout possesses a limited penetration ability and that filtration of the grout occurs if the aperture of a constriction is smaller than a critical value, i.e. when a filter cake forms in front of constrictions in the pow and the great that passes is filtered. In the paper, a model for filtration of grout is presented. When filtration and limited penetration ability are incorporated in the calculations, additional strong effects are observed. This underlines the need of both a representative geometry, including the fracture variability and measurements of grout properties.
|
|
| 5. |
- Nordell, Bo, et al.
(författare)
-
Fracturing of a pilot plant for borehole heat storage in rock
- 1986
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 1:2, s. 195-208
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes research on a pilot plant in Luleå, Sweden. The plant consists of 19 boreholes, 52 mm in diameter, for heat supply and extraction; and 10 boreholes for temperature monitoring. All the boreholes are 21 m deep. The report describes in detail the performance and results of rock mass permeability and borehole permeability tests. It also discusses hydraulic fracturing and explosive fracturing in the boreholes. A simulation model of water flow in the test plant is described. The paper includes conclusions from the test results and recommendations for further study.
|
|
| 6. |
- Nordell, Bo, et al.
(författare)
-
Leaching of rock fractures : Laboratory and field tests for borehole heat stores
- 1989
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 4:1, s. 99-107
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this research project was to increase the hydraulic conductivity of fractured rock by pumping a leaching fluid (NaOH) through rock fractures. A 16-week field test was carried out in a borehole heat store consisting of 19 vertical boreholes to a depth of 15 m in gneissic rock. The leaching process was studied simultaneously in a laboratory test where rock samples from core drillings of the test site were used. The hypothesis that NaOH-solution would leach and thereby widen the fractuers, was not fulfilled. On the contrary, the fractures were sealed as the leaching test went on. The explanation for this is that the leaching rate was higher than expected, the leaching fluid was saturated and the dissolved minerals precipitated. In principle, the minerals were dissolved and moved from one part of the fractures to precipitate at another part, causing clogging. The effect of the leaching field test has been simulated by means of a numerical model. The conclusion is that a leaching of rock as described in this paper should be combined with a deposition tank for the clogging material in order to avoid precipitation in the rock fractures. The results of this project have demonstrated a way of sealing rock fractures that has many more applications in engineering geology.
|
|
| 7. |
- Nordell, Bo
(författare)
-
The borehole heat store in rock at the Lulea University of Technology : constructional and operational experience : The Lulevärme Project 1982-1985
- 1988
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 3:1, s. 85-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Constructional work on the borehole heat store in Lulea was started in August 1982, and the store was started up in July 1983. The work was carried out on a turnkey basis by Svenska Energi System AB (SES), Lulea. The objective of the project is to demonstrate and investigate borehole heat storage technology in this experimental heat store. The actual heat store itself consists of a volume of rock amounting to about 100,000 m**3, beneath an overburden of mineral soil 2-6 m in depth. 120 boreholes have been drilled in the bedrock to a depth of 65 m, and serve as heat exchangers when charging and discharging the store. Much of the research program involves measurements intended to document performance of the store.
|
|
| 8. |
- Nordell, Bo, et al.
(författare)
-
The combi heat store - a combined rock cavern/borehole heat store
- 1994
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 9:2, s. 243-249
-
Tidskriftsartikel (refereegranskat)abstract
- Since 1988, Sweden and Finland have collaborated bilaterally on thermal energy storage with respect to information exchange and collaborative R&D projects. The two countries have both investigated underground thermal energy storage for nearly two decades, and have similar bedrock-the Fenno-Scandian granitic rocks. This paper reviews the work performed in the field of combined rock cavern and borehole heat stores, concerned with construction technology, costs and design principles. One example is an asymmetric store, in the form of 40- to 60-m-long horizontal boreholes between two rock caverns, with the caverns themselves comprising only about 10% of the total storage volume. This design has a specific cost of $US0.40 million/ GWh and $US0.24 million/ GWh for storage capacities of 6 GWh and 36 GWh, respectively. Half of the total construction cost relates to the rock cavern part of the store.
|
|
| 9. |
- Sagefors, Ivar, et al.
(författare)
-
An excavation method for large vertical cylindrical caverns
- 1996
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 11:3, s. 279-285
-
Tidskriftsartikel (refereegranskat)abstract
- Construction of underground storage chambers in rock has traditionally adopted a construction-oriented approach; the cavern design and the method of excavation have been governed by the capabilities of the equipment available. One example is oil storage in unlined horizontal caverns. Today, however, equipment is no longer a limiting factor. The time has come to integrate the construction and operational aspects in the design process. This paper presents a construction concept developed for large vertical rock caverns with a circular or elliptical horizontal cross-section. The method of excavation, called PBM (Pillar Blasting Method), is condensed into a few main operations which are geometrically separated but overlapping in time. PBM is characterized by two main working sites per cavern, and by long-hole bench-drilling, massive blasting rounds, continuous loading and easy ventilation. Recent developments in drilling and blasting techniques are incorporated, such as the water-driven in-the-hole hammer and the electronic ignition system. PBM enables a high rate of excavation and provides a satisfactory working environment with respect to labour safety and human health (a limited exposure to large openings, no exposure to oil mist and to combustion and explosive fumes, etc). Considerable construction cost savings and time savings may thus be achieved compared to conventional methods of excavation for vertical and horizontal caverns of equal storage volume. A preliminary PCT patent (application No PCT/SE95/00324) has been granted. Examples of applications are fresh-water reservoirs, natural gas reservoirs, subsurface hydroelectric pump power plants, and similar objects which require a large underground storage space in preferably unlined rock caverns.
|
|
| 10. |
- Schunnesson, Håkan
(författare)
-
RQD predictions based on drill performance parameters
- 1996
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 0886-7798 .- 1878-4364. ; 11:3, s. 345-351
-
Tidskriftsartikel (refereegranskat)abstract
- In tunnelling and in other underground constructions, a detailed knowledge of the rock mass to be excavated is essential for reasons of safety, reinforcement need and cost and time schedule for the excavation. This paper presents a new approach to how drill performance parameters can be used for rock quality designation (RQD) prediction. Predictions are based not only on traditional parameters as penetration rate and torque, but also on the variability of each parameter which shows a close correlation to fracturing. Since predictions are based on drill monitoring data with high resolution, the prediction can provide detailed information of the structural geometry of the rock mass ahead of the operation. Examples are given from a railway tunnel in northern Sweden built in granitic bed-rock
|
|
