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Grout Experiments We Came to the Following Conclusions: 1

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Grout Experiments We Came to the Following Conclusions: 1 Consolidation of grout element tests Project number Version 403050/3 concept Date December 2002 By order of HSL-zuid Boortunnel Groene Hart. P.O. Box 147 2350 AC Leiderdorp Delft Cluster partner P.O. Box 69 Telephone +31 15 269 35 00 Chambre of commerce NL-2600 AB Delft Telefax +31 15 261 08 21 S41146461 Stieltjesweg 2 [email protected] VAT NL80097476B01 NL-2628 CK Delft www.geodelft.nl Date Summary December, 2002 The rheological properties of grout depend on the water content and the chemical reactions in the grouting material. When grout is applied Version Number of pages in a tail void it will have a pressure higher than the pore pressure of final 10 the surrounding soil and this can lead to consolidation of the grout. The consolidation properties and the rheological properties of the grout used for the Green Heart Tunnel were tested in element tests. A standard oedometer test was used to investigate the compression versus stress curve. A consolidation cell of 0.3 m diameter was used to Title / subtitle investigate the consolidation properties and to test the strength of the Consolidation of grout/ grout at various depths. A simple calculation model will be presented element tests for interpretation of the results. Project name It appears that the stress-strain relation for unconsolidated grout is Groutonderzoek Groene Heart highly non-linear. The consolidation and the resulting removal of water determine the strength of the grout. Project engineer(s) Adam Bezuijen Project companions Other Project members Reference principal Version Date Made by Initials Checked by Initials ir. A. Bezuijen dr.ir. A.M. Talmon Project number Date page 403050/3 December 2002 2 Summary 1Introduction 1 2Oedometer tests3 3Consolidation+vane tests4 3.1 Test set-up 4 3.2 Results 5 3.3 Consolidation properties 7 4References 12 Project number Date page 403050/3 December 2002 3 1Introduction The pressure distribution around a tunnel is of importance for the surface settlement and the tunnel soil interaction. The pressures are partly determined by the grouting process. Injection strategy and grout properties are of importance. In the research project that was started around the Green Heart Tunnel it was decided to measure the grout pressures at various locations on the lining and to determine also the grout properties. This report deals with grout properties at pressures comparable to the injection pressures in the tail void. It was envisaged that at these higher pressures consolidation of the grout could occur leading to a reduction of the water content in the grout. The experiments described in this report therefore focus on the compressibility of the grout and the consolidation properties. Two types of experiments have been performed. Two oedometer tests to determine the relation between compression and stress and a consolidation test for a grout layer that has the same thickness as the grout layer that will be applied for the Green Heart Tunnel. In this consolidation experiment the pore water expelled from the sample was measured as a function of time and the applied stress. The development of strength of the grout was measured with a vane during this experiment. Experiments have been performed with grout material supplied by the contractor of the tunnel. This report describes the set-up of the experiments and presents a first analysis of the results. Suggestions for further analysis will be made. The content of this report is as follows: After a short description of the grout the report deals with the results of the oedometer tests in Chapter 2. Chapter 3 presents a description of the consolidation tests and Chapter 4 presents the results of these tests. Results are discussed in Chapter 5 and the report ends with Chapter 6, Conclusions and recommendations. Project number Date page 403050/3 December 2002 1 2The GHT grout The grout sample was obtained from the normal production for the GHT tunnel. The sample was obtained from the plant in Leidschendam, 30 October at 8:30 and transported to Delft. The experiment started at 10:00. Density and water content were determined. Based on this the following properties were found for a fresh grout sample. Property value dimension water content 0.2011 - density sample 1850 kg/m3 density grains 2231 kg/m3 porosity 0.31 - The initial shear strength was determined with a vane and was approximately 2 kPa, see Figure 6. Project number Date page 403050/3 December 2002 2 3Oedometer tests Two grout samples were tested in an oedometer test. Loading steps were determined from possible loading in reality (substracting the hydrostatic pressure). In principle it is also possible to calculate the consolidation properties form an oedometer test. However, the consolidation process appeared to be too quick. Therefore a larger device was used to measure the consolidation properties, as will be described in the next chapter. Results could be fitted to a power law, see Figure 1. The compressibility appeared to be comparable to the compressibility of the grout that was used for the Sophia Railway Tunnel. 350 300 sample A 250 sample B 200 150 stress (kPa) 100 50 0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 vertical strain (-) Figure 1: Results oedometer test fitted to a power law. The following fit function was used: σ ε b 'v a (3.1) With: ’v : the vertical effective stress on the sample (kPa) the vertical strain (-) a : coefficient (kPa) b : coefficient (-) The following values were found for the coefficients: Sample a b (kPa) (-) A 1.89*106 4.22 B 2.68*106 4.21 Project number Date page 403050/3 December 2002 3 4Consolidation+vane tests 44.1 . 1Test set-up The principle for the test set-up for the consolidation and vane tests is shown in Figure 2. Figure 3 shows a picture of the set-up. 0.284 vane 0.284 air pressure plunger 0.2 grout 0.2 grout dimensions in metres 0.1 sand 0.1 sand drainage Figure 2: Principle test set-up . The left-hand side showed the situation during the vane tests, the right-hand side the set-up during consolidation of the grout. vane Load cell Vessel to collect container expelled water drainage Figure 3: Test setup. The test aims to simulate a part of a consolidating grout layer. The grout thickness is comparable to the thickness of the grout layer in the tail void of the tunnel. The sand simulates the soil and the plunger on top of the grout the lining. Only one side drainage of the grout is allowed, as is the case in the tail void. After some minutes of consolidation at a pressure of 1 bar the pressure was released and the plunger on top of the grout was removed. The vane was placed at various depths and the strength of the grout was tested. The highest shear strength that could be measured was around 10 kPa. At higher shear strengths it was not possible to penetrate Project number Date page 403050/3 December 2002 4 the vane into the grout. The top plate was placed on the grout again after the vane test and consolidation was allowed for another prescribed time. The whole system was saturated before the start of the test and the expelled water from the grout was measured continuously. The amount of water is equal to the decrease in grout volume. The sand underneath the grout was compacted to the maximum density and therefore hardly deforms during the test. The sand used was steep graded sand with a d50 of 442 m, see Figure 4. The sand has a comparable grain size as the Pleistocene sand through which the Green Heart tunnel will be bored to study possible penetration of the grout into the sand. 100 90 80 70 60 50 40 30 20 Percentage passing the sieve 10 0 0.1 1.0 diameter (mm) Figure 4: Sieve curve of the sand used in the sand. The applied stress on the plunger is not exactly equal to the stress exerted on the sample due to friction between the top plate and the container walls. It was determined from tests without samples that 9.96 kPa of air pressure was necessary to overcome the friction. Further on the measurement data have been corrected for this friction. 44.2 . 2Results Figure 5 shows a result of the test. The amount of expelled water and the air pressure above the plunger as a function of time. Clearly the consolidation phases and the ‘vane’ phases could be distinguished. During the latter there was no drainage and a low pressure. Unfortunately a leakage occurs between the plunger and the side walls of the container after 2.6*104 s. After that time the expelled water is also caused by the leakage and air coming trough the sample. Therefore the results after 2.6*104 s will not be used. Project number Date page 403050/3 December 2002 5 1.8 110 1.7 100 1.6 1.5 90 1.4 1.3 80 1.2 70 1.1 1.0 60 0.9 50 0.8 0.7 40 0.6 30 grout pressure (kPa) 0.5 weight pore expelled water (kg) 0.4 20 0.3 weight expel led pore water 0.2 10 air pressure 0.1 0 0.0 -0.1 -10 0·104 1·104 2·104 3·104 4·10 4 5·104 6·104 7·104 8·104 9·104 time (s) Figure 5: Results grout consolidation test. After noticing the leakage it was decided to perform the test once again but without the vane tests.
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