mikkelsen fully grouted piezometer

8/12/2019 Mikkelsen Fully Grouted Piezometer

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Simplify Piezometer Installations, Lower CostsSimplify Piezometer Installations, Lower Costsand Get Better results withand Get Better results with

Fully Grouted PiezometersFully Grouted Piezometers

P. Erik Mikkelsen, P.E.Consulting Engineer GeoMetron Inc PSBellevue, WA, USA

Univ. of Flor ida Short Course, March 19, 2007

Open Standpipe Piezometer Open Standpipe Piezometer Obviously low material costs , but ... Time consuming recording Time-lag potential Minimal and un-timely observations

Installation sensitivity/problems

time consuming backfill procedures complicated backfill risk of incomplete backfill


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VW Piezometer SensorsVW Piezometer Sensors Advantages instant reading, not influenced by observer can be fully grouted best suited for automated readings calibration not influenced by lead length high zero stability (minimal drif t for decades)

Disadvantages vulnerable to over-voltage, need protection calibration factors, barometric influence can be damaged by over-pressure

(After Slope Indicator)


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Fully grouted piezometer Fully grouted piezometer Why grout? Eliminates complexityWhy does it work? It is like saturatedclay!Works like piezo sensor pushed into clayMix design? Design based on cementcontent.

Grout properties (new research results)

Mandrel pushed Mandrel pushed --in VWP in soft clayin VWP in soft clay


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Casagrande missed the point that pressure sensors are different!


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Darcys Law for FlowDarcys Law for Flow

Grout Type Characteristics k (cm/sec) Source Neat cement w/c = 0.53, = 112 pcf 10-7 Baroid

Bentonite chips hydrated 10 -8 Baroid Bentonite slurry 6 % solids 10 -5 Baroid Bentonite slurry 20 % solids 10 -8 Baroid

Cement-bentonite water/solids = 4 to 1 10 -6 Vaughan, 1969Cement-bentonite w : c : b = 4 : 1 : 1 5 x 10 -8 Vaughan, 1973

Table 2. Permeability of some grouts


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CementCement --Bentonite GroutBentonite GroutMix ratio by weight - 2.5 water : 1 cem :0.37 bent + or according to consistencyMix water and cement firs t

Add bentonite slowly, high agitat ion, make groutcreamy, yet pumpable (Marsh # 50-60 sec)Density - 80 pcfWater Content - >100 %Modulus - about 10,000 psi30- day QU strength - 50 to 100 psiPermeabil ity k = 1.0E-06 cm/sec.

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14

Water-Cement Ratio by Weight

U n c o n f i n e d C o m p r e s s i v e S t r e n g t h i n p s i

Marsland, 1973

Slope Indicator, 1982

Dunnicliff, 1980

Anderson, 1984Minnitti, 1980


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VWP in Grout, 200mm thick ness , 288 days cur ing

0

5

10

15

20

25

30

35

40

0.00 5.00 10.00 15.00 20.00

Lapsed Time in Minutes

P r e s s u r e

H e a

d i n F e e

t

Piezometer Chamber


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VWP in Grout, Response Time vs. Curing in Days

200mm grout thickness

0

1

2

3

4

0 50 100 150 200

Curing Time in Days

T i m e

i n

M i n u t e s

50%

90%

95%

100%


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Normalized Cement-Bentonite Grout Properties(Marsh Number = 50 to 60 sec.) Aft er B arr E ng ine erin g 3/9/0 5

0

0.5

1

1.5

2

2.5

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Water-Cement Ratio - w/c

N o r m a l i z e d

V a l u e o f D e n s i t y

, V o i d

R a t i o

&

S t r e n g t h

0

20

40

60

80

100

N o r m a l i z e d

V a l u e o f P e r m e a b i l i t y -

k

Density(pcf) = 83.8 xVoid Ratio = 4 xUCC strength = 240 xk (cm/sec) = 1.0E-7 x


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Fully grouted multiFully grouted multi --level VWPslevel VWPs

Barometric Pressure and Rainfall, Oregon Coast

950

960

970

980

990

1000

1010

1020

1030

10/1/990:00

10/31/9912:00

12/1/990:00

12/31/9912:00

1/31/000:00

3/1/0012:00

4/1/00 0:00

1999 / 2000

m i l l i b a r s o r c m

o f H 2 O

0

0.6

1.2

1.8

2.4

3

3.6

4.2

4.8

R a

i n f a l l p e r

1 2 h o u r s ,

I n c

h e s


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VWP - Altitude Correct ion

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0 2000 4000 6000 8000 10000 12000

Altitu de - Feet

C o r r e c t i o n -

F e e t

0.00

1.00

2.00

3.00

4.00

5.00

6.00

C o r r e c t i o n -

P S I

feet of H2OPSI


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Fully Grouted Piezometer ProjectFully Grouted Piezometer Project

Raw data for fully grouted VWPRaw data for fully grouted VWP


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PROFILE 2: Pore Pressure ElevationsGrnd. Elev. Assum ed = 20 m

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

26.0

28.0

30.0

32.0

1-May-01 1-Jul-01 31-Aug-01 31-Oct-01 31-Dec-01 2-Mar-02

P i e z o m e

t r i c E l e v a

t i o n ,

m e

t e r s

#9, elev. 18.1 m

#8, elev. 18 m

#10, elev. 12 m#12, elev. 10.5 m

#11, elev. 9 m

#13, elev. 8 m

Emb. Elevation

#9 #8

#10

#12

#11#13

PROFILE 1: Pore Pressure Elevations,Grnd. Elev. Assumed = 20 m

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

26.0

28.0

30.0

32.0

1-May-01 1-Jul-01 31-Aug-01 31-Oct-01 31-Dec-01 2-Mar-02

P i e z o m e

t r i c E l e v a

t i o n ,

m e

t e r s

#1, elev. 18.3 m

#3, elev. 11.5 m

#2, elev. 11 m#5, elev. 11 m

#7, elev. 10 m

#6, elev. 6.5

#4, elev. 5 m

Emb. Elevation#4

#6

#7

#5 #2#3

#1


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CC--B grout: 55 gal. paddle mixer B grout: 55 gal. paddle mixer

400400 --m deep Mm deep M --L VWP installationL VWP installation


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ConclusionsConclusionsCement-bentonite grout works!Simpler and faster installationLess chance of failed installationWorks as a high air-entry filter It always starts out fully saturatedEliminates risk of bentonite activity

Applicable to both boreholes andembankments

mikkelsen fully grouted piezometer

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