| 1. |
- Ahnberg, H., et al.
(författare)
-
Stabilising effects of different binders in some Swedish soils
- 2003
-
Ingår i: Ground Improvement. - : Thomas Telford Ltd.. - 1365-781X .- 1751-7621. ; 7:1, s. 9-23
-
Tidskriftsartikel (refereegranskat)abstract
- In Sweden, lime and lime-cement have been used for several decades as stabilising agents in deep stabilisation of soft soils. More recently, other types of binder have come into use, but so far only to a limited extent. In order to gather experience about the effect of various binders, laboratory tests have been performed on different types of soil stabilised with a range of binders. Lime, cement, fly ash and blast furnace slag in different combinations together with different admixtures, such as gypsum, silica fume and calcium chloride, have been used in the investigations. The variation in strength with type of binder has been studied, and comparisons have also been made with results from some previous investigations using different binders. The tests showed that there is no optimal, universal binder for stabilisation of the soils. Whereas some binders are robust, yielding good results in most types of soil, there are also binders that produce very good results in certain soils but poor results in others. Both similarities and differences in effects were found for different binders.
|
|
| 2. |
- Al-Naqshabandy, Mohammed Salim, et al.
(författare)
-
Strength variability in lime-cement columns based on CPT data
- 2012
-
Ingår i: Ground Improvement. - : Thomas Telford Ltd.. - 1365-781X .- 1751-7621. ; 165:1, s. 15--30
-
Tidskriftsartikel (refereegranskat)abstract
- Natural and improved soils have relatively high inherent property variability that should be taken into consideration in design. Investigations of the spatial variability in lime-cement columns are important since they provide a rational quantification of the variability parameters needed for a reliability-based design analysis of geotechnical systems. Statistical analyses are used to evaluate the spatial variability parameters, i.e. the mean, the variance, and the scale of fluctuation, which is the distance within which soil properties reveal strong correlation. This paper presents a field test, in which 30 CPT soundings were performed and analyzed statistically in order to address the spatial variability in a group of lime-cement columns, with respect to the cone tip resistance. The objective of this paper is to describe the statistical analyses and to make a contribution to the empirical knowledge about strength variability in a volume of lime-cement columns. Stationarity has been assessed, and the scale of fluctuation has been evaluated in the vertical and horizontal directions. Random field theory was used based on the sample autocorrelation function ACF. The scale of fluctuation was found to be within the range of 0.2-0.7 m and 2-3 m in the vertical and horizontal direction, respectively. A simple design consideration shows that the variance reduction factor has a major influence on the determination of the design value.
|
|
| 3. |
- Bergman, Niclas, et al.
(författare)
-
Comparing column penetration and total–sounding data for lime–cement columns
- 2014
-
Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 167:4, s. 249-259
-
Tidskriftsartikel (refereegranskat)abstract
- In Sweden, the method commonly used for the quality control of lime–cement columns is the column penetration test. However, it is recommended for depths of no more than 8 m because the probe easily deviates from the column at greater depths. As an alternative to facilitate keeping the probe vertical, a centre hole is normally bored in the column using the total-sounding test method. The aim of this paper is to quantify the agreement between the two methods. If there is good agreement, it should be possible to use the less expensive and less time-consuming total-sounding test as a complement to the column penetration test. The analyses suggest good agreement between the methods, and it is therefore suggested that the total-sounding test be used as a complement to the column penetration test in evaluating the average strength properties of a group of medium- and high-strength lime–cement columns.
|
|
| 4. |
- Fransson, Åsa, 1971, et al.
(författare)
-
Swedish grouting design: hydraulic testing and grout selection
- 2016
-
Ingår i: Ground Improvement. - : Thomas Telford Ltd.. - 1365-781X. ; 169:4, s. 275-285
-
Tidskriftsartikel (refereegranskat)abstract
- © 2016, Thomas Telford Services Ltd. All rights reserved. To ensure successful sealing of rock and soil, an adequate description of the system to be grouted is required as a basis for the grouting design and the selection of the grouting material. In rock, the individual fractures and the hydraulic apertures of these fractures form the basis of the Swedish grouting design concept. The hydraulic aperture is a key parameter when describing grouting behaviour and it is used to determine the extent to which the grout can enter fractures - that is, the penetrability. The hydraulic aperture also determines the penetration length, and therefore the grout parameters (e.g. yield stress and viscosity) as well as the grouting pressure and time needed to be adopted to the hydraulic aperture. Once these parameters are chosen, a suitable grouting technique can be adopted. Simple, practical rock and grout tests are important inputs to ensure correct design and performance. The aim of this paper is to present a testing procedure and provide examples from laboratory and field experience to demonstrate that the approach also works in practice.
|
|
| 5. |
|
|
| 6. |
- Larsson, Stefan, et al.
(författare)
-
A complementary field study on the uniformity of lime-cement columns for deep mixing
- 2005
-
Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 9:2, s. 67-77
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents results from work concerning development of the installation technique of lime-cement columns for ground improvement by deep mixing, as a part of the work of the Swedish Deep Stabilization Research Centre. A second field test was performed in order to test the findings from a previous work published by Larsson et al. The same methodology was adopted as in the previous work. However, the experimental programme was somewhat modified. Statistical analysis of variances, ANOVA, was used to investigate the influence of a number of factors in the mixing process: retrieval rate; number of mixing blades; rotation speed; air pressure in the binder tank; and diameter of the binder outlet hole. The analysis was performed with respect to the stabilisation effect and the coefficient of variation evaluated from hand-operated penetrometer tests on excavated column sections in open test pits. The retrieval rate and the number of mixing blades were found to have a significant effect. The effect of rotation speed, the binder tank air pressure, and the diameter of the outlet hole were insignificant. The two field studies illustrate the importance of performing a sufficient number of tests when studying influencing factors, because the strength is highly stochastic with large variations.
|
|
| 7. |
- Larsson, Stefan
(författare)
-
Binder distribution in lime-cement columns
- 2001
-
Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 5:3, s. 111-122
-
Tidskriftsartikel (refereegranskat)abstract
- The mixing of soil and binders is a very complex process. The object of the mixing process is to distribute the binder and to achieve a satisfactory mixture for the particular purpose. The requirements on homogeneity may differ for each application. The assessment and definition of mixing quality are difficult and very expensive. This paper discusses the concept of mixing quality with respect to the binder distribution, and the use of mixing indices, as a quantitative assessment. The possibility of using mixing indices with the lime–cement column method is taken up. Statistical analysis was performed on a number of samples taken from four lime–cement columns at Arboga, Sweden. The sampling methodology, the scale of scrutiny and thus the influence of the sample size are discussed. The study shows that mixing indices can be used as a quantitative measure of the mixing quality. The results indicate that the sample size has a considerable influence when the mixing quality is poor and a lesser influence when the mixing quality is relatively good. It is also shown that it is difficult to draw conclusions concerning binder distribution from only a few samples, since the distribution may vary. With more extensive knowledge, it may be possible to assess the mixing quality from only a few samples.
|
|
| 8. |
- Larsson, Stefan, et al.
(författare)
-
Probabilistic design of dry deep mixing using an observational approach
- 2015
-
Ingår i: Ground Improvement. - : ICE Publishing. - 1365-781X .- 1751-7621. ; 168:4, s. 300-311
-
Tidskriftsartikel (refereegranskat)abstract
- The evaluation of material parameters for design should consider the spatial variability of measured parameters, the extent and type of tests, and the type and size of the current mechanical system. This is stated in Eurocode 7; however, there is very little guidance as to how this is to be done in practice. The strength and deformation properties of dry deep mixing columns are subject to high variability, and it is difficult to estimate these parameters in advance. Owing to this high variability, probabilistic analyses are considered useful for the design and quality assessment decision procedure. This paper presents a procedure, based on probabilistic analysis, which is a combination of design by calculation and the observational method. The procedure renders the possibility to update acceptance criteria based on measurements during construction, and the methodology rewards the development of the mixing process and increased testing.
|
|
| 9. |
- Larsson, Stefan, et al.
(författare)
-
Uniformity of lime-cement columns for deep mixing : A field study
- 2005
-
Ingår i: Ground Improvement. - : Thomas Telford. - 1365-781X .- 1751-7621. ; 9:1, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- A field study of the mixing process of lime-cement columns for deep mixing has been carried out at a test site in Håby, Sweden. The study aimed to investigate the influence on the stabilisation effect and the coefficient of variation for excavated columns, when a number of factors related to the installation process were varied. The influencing factors investigated were the retrieval rate, number of mixing blades, rotational speed, air pressure in the storage tank, and diameter of the binder outlet hole. A large number of hand-operated penetrometer tests were carried out on the excavated column cross-sections. Statistical multifactor analyses were used to evaluate the influence on the stabilisation effect and the coefficient of variation of the varied factors. The results showed that the retrieval rate and the number of mixing blades were found to have a significant effect. The effect of rotational speed and the diameter of the outlet hole were found to be insignificant. The field study showed that the strength and deformation properties of the soil and the upper pair of mixing blades, with respect to the binder outlet hole, had a major influence on the binder dispersion over the column cross-section. The blade rotation number can be used as an indirect value of the mixing work and can be used as a measure of the mixing tool effectiveness.
|
|
| 10. |
- Palmén, Anders, et al.
(författare)
-
Low-temperature calcite precipitation in sand using CIPS
- 2016
-
Ingår i: Ground Improvement. - : ICE Publishing. - 1365-781X .- 1751-7621. ; 169:1, s. 36-41
-
Tidskriftsartikel (refereegranskat)abstract
- The permeation grouting system CIPS (calcite in situ precipitation system) stabilises granular soil by hydrolysing the urea and causing calcite crystals to precipitate at the contact points of the grains. At low temperatures, the activity of urea hydrolysis is slow, causing concern that the CIPS system might not build sufficient strength in order to be an efficient soil stabilisation method. Most of the documented experience and research have been conducted in Australia; in order to examine the suitability of CIPS under Scandinavian climate conditions, where the operating temperature for the method needs to be adjusted to around 10°C, a laboratory study was conducted. The test cores were all treated and stabilised in a temperature-controlled room simulating Scandinavian ground conditions. After different lengths of curing time, some of the cemented samples were tested saturated for unconfined compressive strength (UCS); the other samples were allowed to dry at either 10 or 20°C before they were tested for UCS. The tests showed a rather obvious increase in strength especially after allowing the spent fluid to deplete, causing the samples to dry out; only a slight difference in UCS increase was recorded between the drying temperature of 10 and 20°C.
|
|
