Single fluid jet-grout strength and deformation properties

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Tunnelling and Underground Spae Tehnology 1 Single fluid jet-grout strength and deformation properties s. Coulter a, C. D. Martin b * athurber Engineering Ltd.

1 Tunnelling and Underground Spae Tehnology 1 Single fluid jet-grout strength and deformation properties s. Coulter a, C. D. Martin b * athurber Engineering Ltd., Edmonton, Alberta, Canada T6E 6AS bdept. Civil & Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada, TOG 2G7 Aepted 2005 August 25 Abstrat The use of sub-horizontal jet-grout olumns in the onstrution of soft ground tunnels is a popular method to provide exavation support. The sequential installation of jet-grout olumns ill a tunneling environment will result in the jet-grout olumns being loaded in a staged manner, resulting in the jet-grout material properties and installation order affeting the magnitude and distribution of surfae settlements and fae deformations. A laboratory program was arried out to quantify the short-term «2;1 hr) development of strength and stifhicss of a grout with a omposition similar to that found in the onstrution of jet-grout olulllns. The laboratory tests were onduted at 8 C to simulate the ground temperatures. Also the laboratory test ylinders were insula-ted to simulate the boundary ondition differenes between 600-mm-diameter jet-grout olumns in soil and the 76-mm-diameter laboratory samples. KCYW01 ds: jet-grout olumns, gout strength, grout stiffness, 1. Introdution The use of jet-grouting in the onstrution of shallow tunnels is beoming inreasingly ommon, partiularly for large tunllels with non-irular profiles. This method uses the installation of a set of sub-horizontal jet-grout olumns to form an arh of emented soil ahead of the tunnel fae to provide exav"ation support (Pelizza and Peila, 1993). The jet-grout arhes are installed in sta.ges to provide a series of overlapping partial one setions (Figure 1). In an urban environment one of the design requirements for shallow tunnels is that the onstrution method mllst. ont.rol surfae settlement. within speified toleranes. However, with jet-grouting there is a delay between the installation of the jet-grout slurry and the hardening of soilement mixture. If this hardening is suffiiently delayed t.he jet-grout olumn ma.y not. have suffiient. shear s\;rength to resist the overburden loads r..<;ulting in exessive settlement above the tunnel and assoiated fae deformations. Beause jet-gtout olumns are usually installed in groups of four or more (see Figure l), this method would appear to have the potential to indue surfae settlements if strit quality ontrol proedures ar not adhered too. An assessment of the development of the strength and stiffness of jet-grout ould help to overome this potential problem. With the knowledge of how the jet-grout hardens the sequening of the installation ould be done suh that the exavation loads indued by the installation of a jet-grout olumn are arried by previous jet-grout olumn installations that have hardened. Sequening in this manner where the exavation loads are supported by the jet- Corresponding author. Tel: +1 (780) , Fax: +1 (780) drk.lilartill@llalberta.a grout olumns with the greatest degree of hardening would provide greater surfae settlement ontrol and exav"dtion support. A laboratory testing program was arried out to determine the short-term «24 hr) development of the strength and stiffness of a grout mix with a omposition similar to that used in the onstrution of jet-grout olumns for tunnel support. In partiular, the laboratory tests were onduted at a typial ground temperature (8 C) rather than the normal room temperature of 20 C. Also the laboratory test ylinders were insulated to simulate the boundary ondit.ion differeneli between t.he 600-mm-diamet.er jet-grout. olumns and the 76-mm-diameter laboratory samples. This paper summarizes the time-dependent material properties of jet-grout from these laboratory tests. 2. Jet-grouting bakground Jet-grouting was developed in Japan in the 1970's and later introdued in Europe, and by the 1980'5 it was in use in North Ameria (Brill et al., 2003). In ontrast to permeation grouting, whih is very sensitive to the type of soils being treated, jet-grouting an be used to treat almost any soil (Brue et al., 1987). The original system used single fluid system of grout omprised of Portland ement and water. The single fluid syst.em an produe olumns up to 500 to 00 mm in diameter and is typially used to onstrut subhorizontal jet grout olumns in tunneling (Kaushinger et al., 1992). Jet-grouting is performed in two phases (Mussger et al., 1987). In the first phase the drill string is advaned by rotary drilling. In the seond phase the jetting is started and the drill string is rotated and withdrawn.

2 Thnnelling' and Underground Spae Tehnology 2 Table 1: Typial parameters used during jet-grouting operations. Parameter Borehole diameter (mm) Number of jets Nozzle diameter (IIlIIl) Grout pump pressure (MPa) Grout mix (Water:Cement) Drilling rod rotation rate (RPM) Withdrawal rate (m/min) Grout injetion rate (m 3 /hour) Range : Typial : Composition of Jet-grout (a) 3D view of jet-grout umbrella. The omposition of jet-grout is partially dependent on the soil being treated. The analytial alulation of the omposition of jet-grout isn't possible in pratie beause of the omplex proesses of erosion, mixing, replaement., filling of pore spae and the jet-grouting parameters (Croe and Flora, 2000). The predition of the jet-grout omposition must then be based upon observations. Croe and Flora (2000) found that the perent soil removal ranged from 30 to 60% in field trials of single fluid jet-grouting it! sandy gravel and silty sand Behavior of jet-grout (b) Typial longitudinal setion showing the jet grout olumns providing the protetive umbrella. Benh exavation Area=81m 2 o 5 m I IL- I (<:) Typial installation sequene for a jet-grout olumn umbrella. Fig. 1: A typial jet-grout protetive umbrella used for a large shallow tunnel. Fully hardened jet-grout behaves muh like Portland ement onrete, i.e., it generally has a non-linear lasti response followed by a brittle failure. Its strength has both a ohesive and a fritional omponent, e.g., Fang et al. (1994) determined using triaxial tests that the ohesion and frition angle of jet-grout in silty sands was 4.2 MPa and 35, respetively. While the properties of fully hardened jetgrout an be readily determined, understanding the proess of the development of strength in jet-grout requires an understanding of the hydration proess of Portland ement. The hydration of Portland ement is an exothermi reation, and as suh the rate of reation is partially dependant upon the reation temperature. As the reatants are onsumed (water and Portland ement) heat is released as the hydrated produts are formed. These hydrated produts, alled the gel, ontribute to the strength of hardened Portland ement. Although the amount of heat released depends on the degree of hydration, the omposition of the hydration produts depends upon the uring temperature (Taylor, 1990). This suggests that the strength of Portland ement is dependent on the time-temperature path of the hydration state. The hydration of ement pastes exhibits at least two and sometimes three yles of heat generation (Figure 2). The first yle is produed immediately after the mixing of the ement with water due to the hydration of trialium aluminate (C 3 A). The rate of heat generation reahes a maximum at about. 5 minutes and then rapidly falls off due to the water beoming saturak'tl with gypsuiil. The first

Tunnelling and Underground Spae Telmology 3 4 1 0; 3.5. -'" I :3 3 1! I.Sl <11 0:: 2.5 I :: I.2 2 j CD :: I CD (!) 1.5 r ;;; CD J: d 2 o I.. '.:., I 0 5 15 20 25 30 35 40 0.5! Fig.

3 Tunnelling and Underground Spae Telmology ; '" I :3 3 1! I.Sl <11 0:: 2.5 I :: I.2 2 j CD :: I CD (!) 1.5 r ;;; CD J: d 2 o I.. '.:., I ! Fig. 2: Heat generation rate for isothermal hydration for normal Portland ement at room temperature, data from Taylor (1990). yle is followed by a period of 1 to 6 hours where the rate of heat generation is very low (Bye, 1983). During this low period the rheology of the paste remains fairly onstant. The seond yle is due to the hydration of trialium siliate (CaS). The peak heat generation in this yle is observed between 6 and hours (Bye, 1983). The derease in the rate of heat generation after this peak is due to two auses: (1) the dereasing amount of reatants (CaS), aud (2) the inhibiting effet of the alium siliate hydrates (CSH) gel oating the remaining reatants (the ement partiles). The initial set ours when the CSH gel begins to interlok between ement partiles on the rising side of this seond yle (Bye, 1983). Beause these temperature effets an impat the hardening and properties of the jet-grout, the laboratory program desribed in the next setion, was speially designed to simulate in-situ heat generation. 3 The grout samples were ast in 76 mm inner diameter by 305 nun long aryli tubes (Figure 3). The tubes were enased in polystyrene insulation with a 200 mm outer diameter. Plasti spaers, 19 mm thik were inserted into the aryli tubes 152 mm apart so that a 2:1 height to diameter ratio sample would be obtained. The spaers were used so that samples with smooth square ends would be produed. This eliminated the need to ap or ut the samples. The spaers had two 12 mm holes to enable the plaement of the grout. The imperfetions on the ends of the samples resulting from these holes were easily removed with a metal sraper. The polystyrene insulation was provided so that the laboratory tests would have a similar time-temperature history as a jet-grout olumn installed in the field. This was neessary beause of the dependeny of the strength of hardened ement on the time-temperature history that it experienes. The uring of the gtout was performed in a temperature-ontrolled room with an ambient temperature of 8 C, and temperature of the grout reorded with thermistors during hydration. The temperature of 8 C was hosen as it is similar to ground temperatures enountered in shallow tunneling in many temperate ountries. The required thikness of the insulation was determined using the finite differene method to simulate radial heat flow from a ylindrial sonre (600-mm-diameter jet-gront <:oluilln in the field versus 76-1I11Il-diarneter grout sample Endapl 3. Laboratory testing of jet-grout properties To haraterize the properties of jet-grout, 41 speimens were tested to determine the development of strength and stiffness as a funtion of time. The testing foused on the period from the initial setting to 24 hours of uring. The Young's modulus, uniaxial ompressive strength, and Brazilian tensile strength were tested at approximately 6, 7, 8.5,.5, 13.75, 18.5 and 24 hours, and also at 2, 3 and 28 days Testing proedure The water to ement ratio of the jet-grout tested was 1:1 by weight. The grout was proportioned to be the same as jet-grouting with 50% soil removal. The aggregate was silty-sand from a glaial outwash deposit in the Edmonton, Canada area and the ement was Canadian Standards Assoiation (CSA) Type 30, a high-early-strength Portland ement. Fig. 3: Configuration of t.he grout mould Il!'iOO to reate the laboratory samples.

4 Tunnelling and Underground Spae Tehnology 4 Table 2: Thermal properties used in the finite differene model. Material k C p kj/(m C) kj/(m:3oc) Grout Insulation Sand in the laboratory) into an insulator (soil in the field versus polystyrene insulation in the laboratory). Coulter (2004) showed that the a 200 mm outer diameter of polystyrene insulation was required for the grout in the laboratory to have a similar average temperature history as the jet-grout olumn in t.he field for the initial 24-hour p<'riod. This amount of insulation provided a laboratory simulated temperature history that had an average temperature over 24 hours of 3.5% higher than the field simulation. The thermal properties llsed in t.h finite differene model ar shown in Table 2. Coulter (2004) onduted a sensitivity analysis of the finite differene mathing tehnique to the thermal properties used in the analysis and onluded that the errors generated were less than % Testing results The testing results showed that the grout had an initial set at approximately 6 hours after initial mixing. At this time the grout had suffiient str<'llgth so that the 76-mmdiameter samples were apable of being removed from the moulds without signifiant damage, although they were still soft enough to be indented by areless handling. Hardening of the grout was rapid following this, with the greatest rates of hardening in the first 24 hours. Additionally there appeared to be a transition in the nature of the grout at approximately 11 hours. At this time the material behavior hanged from plasti to brittle, the rate of inrease of the unonfined ompressive strength and the Young's modulus reahed a peak, and the rate of temperature inrease was a maximum. The unonfined ompressive strength (UCS) was ohserved to initially inrease with time with a power-type relationship, i.e, the rate of strength gain was inreasing with time. This is observed in Figure 4a as the straight line portion up to approximately.5 hours at whih time the rate of strength gain is at its gteatest. Beyond.5 hours the rate of strength gain slows with time. The 28-day strength has a mean of 14.2 MPa with a standard deviation of 0.75 MPa. Equation 1 represents the strength for times less than.5 hours and Equation 2 represents the strength for times greater than.5 hours. The units for time (t) are in hours and the units for unonfined ompressive strength (UeS) are in kpa. UCS = x 1O-4tli.li38 UCS = 881n(t ) < 1O.5hours (1) > 1O.5hours (2) 00. ::: 0 E 8 0;:: 8 ::J to g> I!! Cii Q).!!.!!! 'i:i!!! III (a) Uniaxial ompressive strength I --r--- Test Data --Regression 0.1 '---'--'-.L-L-'- -'- '----L_",--",-.L...J 00 (b) Brazilian tensile strength () Young's modulus : Test Data --Regress.," Fig. 1\: Development of the unonfined omprc'.c:;fiive strength, Brazilian tensile strength and the tangent Young's modulus with time

Tunnelling and Underground Spae Tehnology 5 Vane shear tests were also arried out to determine the shear strength between 3.5 hourli and 5.5 hours.

5 Tunnelling and Underground Spae Tehnology 5 Vane shear tests were also arried out to determine the shear strength between 3.5 hourli and 5.5 hours. These tests gave shear strength ranging from approximately 1 kpa at 3.5 hours to approximately 20 kpa at 5.5 hours. The strength gain an be approximated by Equation 3. Vane shear strength = 1.1 x 1O- 4 t 7. 1 (3) The tensile strength development with time (Figure 4b) had a similar shape as t.he unonfined ompressive strength development in Figure 4a, but with slightly more satter in the data. The average ratio of tensile strength to ompressive strength was The Young's modulus was alulated as the tangent stiffness at 50% peak stregllth. Th developmnt of the Young's modulus with time also has a similar shape as the development ofucs with time (Figure 4). Equation 4 represents the Young's modulus for times less than.5 hours and Equation 5 represents the modulus for times greater thall.5 hours. The units for time (t) are ill hours and the units for the Young's modulus (E) are in MPa. E = x 1O-4t5.697 E = 184.3In(t ) < IO.5hours (4) > 1O.5hours (5) The relationship between uniaxial ompressive strength and Young's modulus is shown in Figure 5. This relationship an also be observed in the stress-strain urves in Figure6. The stress-strain behavior of the samples tested at times less than.5 hours is shown in Figure 6a. These samples have a dutile post-peak behavior. The transition to a brittle type of failure appears to our at.5 hours, when the unonfined ompressive strength is approximately 650 kpa. Figure 6b learly shows a brittle response and that the strain to failure inreases with inrea..;ing peak strength, illustrating how the rate of strength gain is greater than the rate of stiffness gain. The mean room temperature during the ourse of the testing was 8.3 C, with a standard deviation of 0.25 C. As y = 0.82 xa(0.83) m- Il. til ::J 600 :i "t:j 0 :E til 400-0) C ::J 0 >- 200 shown in Figure 7a, the first yle of hydration raises the grout temperature by 8.8 C and OCC-IITS in t.he first hour after mixing. This is followed by approximately 5 hours of steady temperature and then a signifiant temperature gain between 5 and 15 hours. The rate of temperature gain reahes a peak value at approximately 11 hours (Figure 7b). The strong orrelation between the hange in grout strength and temperature hange an be seen by omparing FigllTs 4 and 7. The signifiant strength gain ours during the seond yle of hydration, i.e., between 5 and 15 hours. It is likely that at times less than 6 hours the hydration doesn't ontribute to signifiant strength gain beause the ement gel is still disontinuous. 4. Disussion A laboratory testing program was arried out to evaluate the properties of a typial grout mixed used in the installation of horizontal jet-grout olumns that form a protetive m Il. Co 300 til en r Q. '"! en v 'ii_ -v Strain (mlm) (a) Less than.5 hours Groul Age (hours) e v tl ' v _.. -oz '''1--'' v - Groul Age (hours) =:.= :g v.3 D Uniaxial Compressive Strength (kpa) SIrain (mlm) (b) Greater than lo.5 hours Fig. 5: Relationship between uniaxial ompressive strength and Young's modulus. Fig. 6: Stress-strain urves rp.rorded for the unronfined ompressive tests for grout at various times.

Tunnelling and Underground Spae Tehnology 6 umbrella for tunnel onstrution and support. The sale differene betwe<'n the 600-mm-diamter j<'t-grollt.

6 Tunnelling and Underground Spae Tehnology 6 umbrella for tunnel onstrution and support. The sale differene betwe<'n the 600-mm-diamter j<'t-grollt. olumns and th 76-mm-diamtr laboratory samples was overome by plaing the laboratory samples in an insulating ylinder in a hamber kept at a onstant temperature. A finite differene tehnique was used to determine the thikness of the insulation suh that the hat gneration and transfer to the soil was properly simulated in the laboratory onditions. The initial temperature of the laboratory samples and the uring hamber was kept at 8 C, to simulate the tmperature of th ground enounterd in shallow tunneling in many temperate ountries. Th laboratory results larly show a 6 hour period prior t.o the onset of hardening. At this stage the grout has essentially no measurable uniaxial ompressive strength or st.iffness. After this 6-hour period t.here' is a very rapid inrease iu strength and stiffness whih ontinues up to approximately 12 hours after initial mixing. After this the hardening proess ontinues, but at a slower rate. The 35 strength and stiffness properties all show a strong orrelation with temperature and hene temperature measurements in the field may be a useful iudiator for estimating strength and stiffness. Surfae settlements and fae deformations an be ontrolled using horizontal jet-grout olumns for exavation support (Mussger et al., 1987; Pelizza and Peila, 1993). However: as indiated by this study the timing and squening of the jet-grout installations must linked to the strength and deformation properties of the grout. Suffiient time must be allowed between adjaent olumn(s) installations to allow th grout to hardn s11h that adquate tunnel support is provided by the jet-grout umbrlla. The laboratory properties developed from this study may help designers and ontrators attempting to optimize the installation sequne of a jt-gront umbrlla_ Aknowledgements This work was supported by the Natural Sienes and Engineering Researh Counil of Canada. G 0 :::l CIl a. E CIl I e---.'...--::: Cast 3 Cast Cast 5 --O-Cast (a) Temperature hange with time Cast 3 -+-Cast5-2 L-'--'---'---'---'--'--'--'--'--'--'--'--'--'--'--'---'---'---'---' o 5 (b) Rate of temperature hange Fig. 7: Grout temperature hange reorded at various times. Referenes Brill, G. T., Burk, G. K., Ringn, A. R., A ten yar perspetive of jet grouting: Advanements in appliations and tehnology. In: Johnsen, L., Brue, D. A., Byle, M. (Eds.), Proeedings 3rd International Conferene - Grouting and Ground Treatment, New Orlealls. Vol. 1 of Geotehnial Speial Publiation No_ 120. Amerian Soiety of Civil Engineers: pp Brue, D. A., Boley, D. 1., Gallavresi, F., New developments in ground reinformnt and treatmnt for tuilnelling. In: Pro Rapid Exavation and Tunnelling Conferene, New Orleans. Soiety of Mining Engineers, Littleton, CO, pp Bye, G. C., Portland Cemnt: omposition, prodution and properties. Pergamon Press, New York, 149p. Coulter, S. N. P., Influene of tunnel jet-grouting on ground deformations at the Aesher 'Ilmnel, Switzerland. Master's thesis, Dept. Civil and Environmntal Engineering, University of Alberta, Edmonton, Alberta. Croe, P., Flora, A., Analysis of single fluid jet grouting. Geothniqlle 50 (6), Fang, Y.-S., Liao, J..1., Lin, T.-K., ehanial properties of jet grouted soilrete. Quarterly Journal of Engineering Geology 27 (3), Kaushinger,1. J., Hankour, R., Perry, E. B., Methods to estimate the omposition of jet grouted bodis. In: ASME Speial Publiation No. 30. Amerian Soiety Mehanial Engineers, New Orleans, LA, USA, pp Mussgr, K., Koinig, J., Rishl, S., let grouting in ombination with NATM. In: Proeedings Rapid Exa V"dtion and Tunnelling Conferene, New Orleans. Soiety of Mining Engineers, In., Littleton, CO, pp Plizza, S., Pila, D., Soil and rok reinforements in

7 Thnnelling and Underground Spae Tehnology 7 tunnelling. Tunnelling and Underground Spae Tehnology 8 (3), Taylor, H. F. W., The Chemistry of Cements. Aademi Press In., New York, 459p.

Mechanical Properties of High-Strength Concrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2

Mechanical Properties of High-Strength Concrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2 1.1 Introdution Mehanial Properties of High-Strength Conrete Manish Kumar 1, A.M. ASCE; Zhaoyu Ma 2 ; Moses Matovu 2 Mehanial properties of High-Strength Conrete (HSC) an be divided in two groups as shortterm