• Aucun résultat trouvé

Equipment and methods for soil frost action studies

N/A
N/A
Protected

Academic year: 2021

Partager "Equipment and methods for soil frost action studies"

Copied!
18
0
0

Texte intégral

(1)

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

Internal Report (National Research Council of Canada. Division of Building

Research), 1985-08-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=aea67ea3-9f22-459e-aecc-2d13200f879b https://publications-cnrc.canada.ca/fra/voir/objet/?id=aea67ea3-9f22-459e-aecc-2d13200f879b

NRC Publications Archive

Archives des publications du CNRC

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/20337913

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Equipment and methods for soil frost action studies

(2)

NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH

DBR INTERNAL REPORT NO. 503

EQUIPMENT AND METHODS FOR SOIL FROST ACTION STUDIES

by E . Penner and D . Eldred

Checked by: Approved by:

Prepared for: Record Purposes

ABSTRACT

ANALYZED

Date: August 1985

This paper d e s c r i b e s methods developed by t h e authors f o r s t u d i e s o f f r o s t a c t i o n i n s o i l s , and t h e DBR f a c i l i t i e s f o r t h e s e

(3)

EQUIPMENT AND METHODS FOR SOIL FROST ACTION STUDIES

E. Penner and D. E l d r e d

T h i s r e p o r t i s a r e c o r d of t h e c u r r e n t methods and f a c i l i t i e s f o r s o i l f r o s t a c t i o n s t u d i e s a t DBR d e v e l o p e d by t h e a u t h o r s .

The c u r r e n t phase of t h e f r o s t a c t i o n s t u d i e s commenced when a f r o s t c e l l d e s i g n e d and d e v e l o p e d by W.A. S l u s a r c h u k of N o r t h e r n E n g i n e e r i n g S e r v i c e s (NES) was a c q u i r e d . The c e l l was m o d i f i e d , p a r t i c u l a r l y w i t h r e s p e c t t o t h e method of a p p l y i n g t h e o v e r b u r d e n p r e s s u r e and t h e s u p p l y of w a t e r t o t h e s o i l sample, b u t t h e f e a t u r e t h a t was u n i q u e , and r e t a i n e d , i s t h e upside-down d i r e c t i o n of f r e e z i n g of t h e sample. I n a d d i t i o n , i n t h e NES c e l l t h e sample i s a l l o w e d t o a d f r e e z e t o t h e w a l l s of t h e sample h o l d e r . Heaving d i s p l a c e m e n t due t o l e n s i n g and e x p a n s i o n r e s u l t i n g from t h e w a t e r l i c e phase change of p o r e w a t e r i s accommodated by t h e s l i d i n g of t h e u n f r o z e n p o r t i o n i n s i d e t h e c e l l . T h i s d o e s n o t e r a d i c a t e a l l

f r i c t i o n a l r e s i s t a n c e t o h e a v i n g , b u t c a l i b r a t i o n of t h e f r i c t i o n i s

p o s s i b l e and, of c o u r s e , no d i f f i c u l t i e s a r e e n c o u n t e r e d when no o v e r b u r d e n p r e s s u r e i s a p p l i e d .

The l a b o r a t o r y f r e e z i n g t e c h n i q u e a d o p t e d is t h e ramped f r e e z i n g method i n i t i a t e d by t h e North-West A l a s k a (NWA) f r o s t heave program. T h i s

t e c h n i q u e i n v o l v e s t h e s y s t e m a t i c l o w e r i n g of t h e t e m p e r a t u r e a t b o t h e n d s of t h e sample a f t e r i n d u c i n g c r y s t a l l i z a t i o n . The most i m p o r t a n t a d v a n t a g e of t h e ramping method i s t h a t r a t e s of f r o s t p e n e t r a t i o n s i m i l a r t o t h o s e below a c h i l l e d g a s p i p e l i n e can be s i m u l a t e d i n t h e l a b o r a t o r y .

The ramp t e m p e r a t u r e g e n e r a t i o n and t e m p e r a t u r e c o n t r o l of t h e sample was improved a t DBR by c o m p u t e r i z a t i o n , which h a s l e d t o g r e a t e r c o n t r o l o f t h e o v e r a l l f r e e z i n g p r o c e s s .

METHODS AND MATERIALS F r o s t c e l l

F i g u r e 1 shows t h e c u r r e n t v e r s i o n of t h e f r o s t c e l l , which c o n t a i n s t h e m o d i f i c a t i o n s made t o t h e NES c e l l d e s i g n . I t s h o u l d be n o t e d t h a t f r e e z i n g i s from t h e bottom up

-

a major i n n o v a t i o n t o l a b o r a t o r y f r e e z i n g of s o i l s i n t h e o r i g i n a l NES c e l l . The p l a t e a t t h e t o p of t h e specimen i s t h e s o - c a l l e d warm end. T h i s p l a t e h a s p r o v i s i o n f o r c i r c u l a t i n g

t e m p e r a t u r e - c o n t r o l l e d l i q u i d and t h e s u p p l y of w a t e r t o t h e sample t h r o u g h a porous p l a t e . The warm p l a t e r e s p o n d s t o t h e movement i n d u c e d by i c e s e g r e g a t i o n and p r o v i d e s a c o n v e n i e n t l o c a t i o n t o measure heave w i t h time. S i n c e X-rays a r e u s e d t o l o c a t e i c e growth, m e t a l o b j e c t s must n o t o b s t r u c t t h e X-ray beam i n t h e r e g i o n between t h e X-ray g e n e r a t o r and t h e f i l m .

A t h i n t e f l o n f i l m s h e e t i s g l u e d t o t h e i n s i d e of t h e c e l l t o r e d u c e f r i c t i o n between t h e c e l l w a l l and t h e u n f r o z e n s o i l . The t h e r m i s t o r l e a d s and t h e t h e r m i s t o r s l i e i n a s h a l l o w g r o o v e immediately b e h i n d t h e t e f l o n s h e e t . The g r o o v e s c i r c l e t h e c e l l w a l l a t r i g h t a n g l e s t o t h e d i r e c t i o n of

(4)

h e a t flow. Thus, t h e t h e r m i s t o r l e a d s l y i n g i n a n i s o t h e r m a l p l a n e i n t h e c e l l r e d u c e t e m p e r a t u r e e r r o r s r e s u l t i n g from t h e r m a l c o n d u c t i o n . Tenney C o n t r o l l e d E n v i r o m e n t a l Chamber A commercial c o n s t a n t - t e m p e r a t u r e a i r chamber i s u s e d t o h o u s e t h e f r o s t c e l l d u r i n g t h e f r e e z i n g p r o c e s s . The t e m p e r a t u r e i n t h e Tenney Chamber i s c o n t r o l l e d a t a b o u t +O.l°C. A c o n s t a n t t e m p e r a t u r e e n v i r o n m e n t around t h e c e l l r e d u c e s v a r i a b l e h e a t l o s s e s from t h e sample d u r i n g t h e f r e e z i n g p r o c e s s . There i s , however, a m a t t e r of o v e r a l l h e a t l o s s e s t h r o u g h t h e s i d e s of t h e c e l l . Chamber t e m p e r a t u r e s a r e k e p t a t a b o u t t h e a v e r a g e of t h e sample-end t e m p e r a t u r e s . T h i s r e d u c e s t h e unwanted h e a t l o s s e s from t h e sample t o manageable v a l u e s . The f l a t n e s s of t h e i c e l e n s e s a t t e s t s t o i t s s u c c e s s .

P h i l i p s X-Ray Equipment

A p o r t a b l e 200 KV X-ray g e n e r a t o r i s u s e d t o p i n p o i n t t h e l o c a t i o n of t h e growing i c e l e n s w h i l e h e a v i n g i s i n p r o g r e s s . T h i s e n a b l e s t h e i c e l e n s t e m p e r a t u r e s t o be a s c e r t a i n e d and i s f u n d a m e n t a l t o t h e problems u n d e r i n v e s t i g a t i o n . The Tenney Chamber h a s a s t e e l a c c e s s door which must remain open w h i l e e x p o s i n g t h e sample t o X-rays. An i n n e r d o o r c o n s t r u c t e d of p l a s t i c i s u s e d t o k e e p X-ray f i l m e x p o s u r e t i m e low and s t i l l m a i n t a i n a c o n s t a n t t h e r m a l environment i n s i d e t h e chamber. By t r i a l and e r r o r i t was e s t a b l i s h e d t h a t t h r o u g h t h e p l a s t i c door an e i g h t minute e x p o s u r e t i m e a t f u l l power i s s u f f i c i e n t t o p r o v i d e t h e r e q u i r e d p h o t o g r a p h i c d e t a i l . An I n d u s t r i x AA f i l m i s sandwiched between one s e t of f l u o r o m e t a l l i c (Kyoyko

SMP 1 0 8 ) and one s e t of 0.010 i n c h (0.254 mm) l e a d i n t e n s i f y i n g s c r e e n s .

During e x p o s u r e t h e f i l m h o l d e r i s mounted b e h i n d t h e c e l l i n s i d e t h e chamber. The X-ray beam was c o l l i m a t e d s o t h a t t h e image would c o v e r t h e

8+ x 11 i n c h f i l m . Because of t h e l o c a t i o n of t h e f i l m r e l a t i v e t o t h e c e l l

t h i s g i v e s a s l i g h t l y l a r g e r image t h a n t h e a c t u a l s i z e of t h e f r o z e n

sample. A d i s t a n c e of a b o u t 2 metres s e p a r a t e s t h e X-ray g e n e r a t o r and t h e X-ray f i l m .

Modified IIotpack R e f r i g e r a t e d L i q u i d Bath C i r c u l a t o r

Hotpack b a t h s a r e u s e d t o s u p p l y t e m p e r a t u r e - c o n t r o l l e d l i q u i d f o r t h e f r o s t c e l l - e n d h e a t e x c h a n g e r s . C i r c u l a t i n g f l u i d s u s e d f o r t h e two sample-end t e m p e r a t u r e s a r e computer c o n t r o l l e d . A t h i r d b a t h p r o v i d e s a r e a d y s o u r c e of c h i l l e d l i q u i d t o i n d u c e c r y s t a l l i z a t i o n a t t h e s t a r t of e a c h h e a v i n g e x p e r i m e n t . To p r o v i d e computer c o n t r o l of t h e l i q u i d b a t h t e m p e r a t u r e s , a n

e l e c t r i c a l r e s i s t o r was added t o one l e g of t h e w i r e l e a d between t h e b a t h t e m p e r a t u r e s e n s o r and one l e g of t h e Wheatstone b r i d g e of t h e h o t p a c k c o n t r o l l e r . With a s p e c i a l multiprogramrner ( c u r r e n t d i g i t a l t o a n a l o g c o n v e r t e r ) a c o m p u t e r - c o n t r o l l e d c u r r e n t s u p p l y of up t o f20.00 ma was p r o v i d e d a c r o s s t h e i n s t a l l e d r e s i s t o r of t h e t e m p e r a t u r e b a t h . The

s m a l l e s t o u t p u t s t e p w i t h t h e HP multiprogrammer i s 0.01 ma, which w i t h t h e h o t p a c k t e m p e r a t u r e b a t h s , g a v e a t e m p e r a t u r e change of 0.0015°C.

The m o d i f i c a t i o n t o t h e t e m p e r a t u r e c o n t r o l of t h e Hotpack l i q u i d b a t h c i r c u l a t o r i s shown i n F i g u r e 2. With t h i s a p p a r a t u s v a r i o u s t e m p e r a t u r e -

(5)

controlled freezing sequences can be programmed. They are used most

frequently to reduce the end temperatures uniformly with time, e.g.,

0.02OC

per day. When this is done at both ends of the sample, a controlled frost

line penetration into the sample is achieved.

The program for controlling the end temperatures has most of the

elements of a proportional controller. The system's digital voltmeter reads

the temperature of the sample's end. The programmed temperature sampling

and adjustment frequency depends on the magnitude of the error signal.

If

the end temperature is different from the required set temperature (error

signal), the multiprogrammer signals a current change to the bath resistor

and the bath temperature changes accordingly. When the computer is

programmed to ramp the end temperature at a rate of 0.02OC/day with a 10 ohm

signal resistor, it does it in steps of 0.0015°C.

Hence, the set

temperature is changed approximately every 108 minutes. Greater frequency

is possible if the daily rate of temperature change is larger.

Guildline Temperature Bath for Calibrating Thermistors

The temperature of the calibration bath is measured with a Model 9535

Guildline thermometer having a resolution of O.OOl°C and a claimed accuracy

of O.Ol°C over a 24 hr. period. The Guildline thermometer is calibrated

monthly with a standard platinum resistance thermometer to

4

O.OOl°C to

assure continued accuracy.

The glass-encased thermistors to be installed in the frost cell are

calibrated using the HP temperature measuring system also used for actual

frost heaving experiments. Prior to calibration the thermistors are given

the usual stabilizing thermal shock treatment of 10-20 alternate exposures

to ice bath and boiling water temperatures.

Computer System

The new HP 1000, Series A600, Model 6 computer replaced the HP 9835,

and

is

running under the RTE-A operating system. It is now fully

operational. A 2623/2671 graphics terminal, a 7910 twelve megabyte disc

drive, a 7908 16.5 megabyte disc and a 2631 printer are on one HPIB. A

3455A voltmeter, a 3495A scanner and a 6942A multiprogrammer are on a second

HPIB, and a 72456 plotter is on a third HPIB. With this arrangement,

plotting and printer operations do not interfere with the temperature

control of the frost cell or the temperature ramping program. A photograph

of the frost heave facilities is shown in Figure 3.

A list of the frost

action software programs appears below.

Data Acquisiton Programs

(1) Data acquisiton start-up and initialization.

(2) Scan channels, measure, compute, post data to extended

memory area and disc, file and print results.

(3) Water reset.

(4)

Change scan period.

(6)

Temperature Control Programs

(1) Cold side control start-up and initialization.

(2) Cold side control with ramp function.

(3) Cold side control status output to terminal.

(4)

Manual change of cold side control parameters.

(5) Warm side control startup and initialization.

(6) Warm side control with ramp function.

(7) Warm side control status output to terminal.

(8)

Manual change of cold side control parameters.

(9) Manual setting of cold side temp.

(10) Manual setting of warm side temp.

(11) Cold side control status to printer.

(12) Warm side control status to printer.

Graphics Programs

(1) Frost action plot to terminal

(isotherm, water heave, total heave and segregation ratio).

(2) Frost action plot to 72458 plotter.

(3) Cold side and warm side temperature plot to terminal.

(4)

Cold side and warm side temperature plot to 72458 plotter.

(5) Single record (1 scan) temperature profile vs depth with

digitizing function to terminal.

(6) Single record (1 scan) temperature profile vs depth with

digitizing function to 72458 plotter.

Utilities Programs

1)

Cold side temperature (Cell 1) manual read.

2)

Warm side temperature (Cell

1) manual read.

3) Cold side temperature (Cell 2) manual read.

(4)

Warm side temperature (Cell 2) manual read.

(5)

Disc data file initialization.

(6)

Disc data file read to extended memory area.

(7) Function keys definition

1.

(8)

Function keys definition 2.

Preparation of Soil Specimen and Placement

The frost cell (Figure 1) may be used for both undisturbed and

remoulded soils. However, the cell is designed and so best suited for

remoulded samples. Details on specimen preparation will be confined to

remoulded soils.

Sample homogeneity and reproducible specimen preparation are basic to

carrying out reproducible experiments. Ice lens growth and heaving are

generally extremely sensitive to variations.

Preparation of specimens may begin either with air-dried soils or with

soils at their field moisture content. Air-dried soils are usually ground,

sieved and mixed thoroughly as a pretreatment to wetting.

(7)

Water i s added g r a d u a l l y d u r i n g mixing w i t h a handheld e l e c t r i c b l e n d e r t o b r i n g t h e s o i l t o 1 o r 2% above t h e l i q u i d l i m i t . The w e t s o i l i s t h e n s t o r e d f o r s e v e r a l d a y s i n s e a l e d c o n t a i n e r s .

P r e p a r a t i o n of t h e specimen i s done d i r e c t l y i n t h e f r o s t c e l l . A f t e r mixing t h e w e t s o i l a g a i n , i t i s poured i n t o t h e c e l l s l o w l y t o a v o i d l a r g e bubble entrapment. The u p p e r p a r t of t h e c e l l i s t h e n p l a c e d o v e r t h e lower s e c t i o n and t h e c o n s o l i d a t i o n p r o c e s s c a n begin.

The c o n s o l i d a t i o n program depends on t h e t y p e of f r e e z i n g e x p e r i m e n t t o b e c a r r i e d o u t . R e p r o d u c i b i l i t y of f r e e z i n g r u n s , however, do depend t o a l a r g e e x t e n t on r e p r o d u c i b l e d e n s i t i e s . The sample may be c o n s o l i d a t e d t o e q u i l i b r i u m a t t h e o v e r b u r d e n p r e s s u r e r e q u i r e d f o r t h e f r e e z t n g p r o c e s s , o r specimens may be c o n s o l i d a t e d t o a common p r e s s u r e f o r c o m p a r a t i v e f r e e z i n g e x p e r i m e n t s .

The f r o s t c e l l i s p l a c e d i n s i d e t h e c o n s t a n t t e m p e r a t u r e chamber a f t e r c o n s o l i d a t i o n . The w a t e r s u p p l y system i s u s u a l l y f l u s h e d w i t h d e a i r e d w a t e r t o p u r g e any

a i r

b u b b l e s c a u g h t i n t h e system. The sample i s t h e n

allowed t o e q u i l i b r a t e t h e r m a l l y , w i t h t h e w a t e r i n t h e s u p p l y system, and u n d e r t h e s t a r t i n g o v e r b u r d e n p r e s s u r e . C i r c u l a t i o n of c o n t r o l l e d t e m p e r a t u r e l i q u i d s may be s t a r t e d a t t h i s s t a g e t h r o u g h t h e end h e a t e x c h a n g e r s . The u s u a l p r o c e d u r e i s t o have t h e c o n t r o l l e d - t e m p e r a t u r e l i q u i d s c i r c u l a t i n g t h r o u g h t h e warm-end h e a t exchanger a t t h e s t a r t i n g t e m p e r a t u r e and t h e cold-end l i q u i d s c i r c u l a t i n g a t t h e s t a r t i n g t e m p e r a t u r e b e f o r e f r e e z i n g u n t i l t h e r m a l e q u i l i b r i u m i s a t t a i n e d . It i s t o be n o t e d t h a t most s a t u r a t e d s o i l s w i l l n o t c r y s t a l l i z e s p o n t a n e o u s l y i n t h e c e l l above -1 O C . I n i t i a t i n g I c e C r y s t a l l i z a t i o n i n t h e Sample I n i t i a l i z a t i o n of f r e e z i n g i s c a r r i e d o u t by c i r c u l a t i n g c h i l l e d l i q u i d t h r o u g h t h e sample c o l d - s i d e h e a t exchanger from a s e p a r a t e h o t p a c k c o n s t a n t t e m p e r a t u r e t a n k u n t i l c r y s t a l l i z a t i o n t a k e s p l a c e . B e f o r e t h i s o p e r a t i o n i s s t a r t e d , t h e sample i s a t t h e r n a l e q u i l i b r i u m w i t h warm and c o l d - s i d e l i q u i d c i r c u l a t i n g b a t h s . The c o l d - s i d e l i q u i d f l o w t h r o u g h t h e h e a t

exchanger i s s t o p p e d and l i q u i d from a t a n k a t about -lO°C i s c i r c u l a t e d f o r a s h o r t p e r i o d . A t t h e same t i m e t h e computer s c r e e n i s programmed t o show t h e t e m p e r a t u r e of t h e s o i l o n t h e c o l d - s i d e a t a p p r o x i m a t e l y one second i n t e r v a l s . When t h e -10°C l i q u i d i s c i r c u l a t e d , t h e t e m p e r a t u r e on t h e c o l d s i d e s l o w l y d e c r e a s e s . A t c r y s t a l l i z a t i o n t h e c o l d - s i d e t e m p e r a t u r e rises s u d d e n l y b e c a u s e of l a t e n t h e a t r e l e a s e . A t t h i s p o i n t t h e -lO°C c t r c u l a t i n g f l u i d i s c u t o f f and t h e c o l d - s i d e c o n t r o l t a n k l i q u i d i s a g a i n c i r c u l a t e d t h r o u g h t h e c o l d - s i d e h e a t exchanger. The t e m p e r a t u r e of t h e sample r e v e r t s t o t l ~ e p r e f r e e z i n g t e l n p e r a t u r e s . The o n l y d i f f e r e n c e i s t h a t f r e e z i n g i s now t a k i n g p l a c e : w a t e r movement e i t h e r i n t o o r o u t of t h e sample o c c u r s (depending on s o i l t y p e and thermal c o n d i t i o n s ) and h e a v i n g i s e v i d e n t .

C o n t r o l l e d F r e e z i n g R a t e and Data R e c o r d i n g

A f t e r c r y s t a l l i z a t i o n t h e t e m p e r a t u r e p a t t e r n t o be f o l l o w e d a t h o t h e n d s of t h e sample i s e x e c u t e d by t h e computer. T h i s may he a t e m p e r a t u r e ramping p a t t e r n a t b o t h e n d s a t any d e s i r e d r a t e , e g g . 0.02OC d e c r e a s e p e r day, c o n s t a n t t e m p e r a t u r e s a t h o t h e n d s , o r c o n s t a n t t e m p e r a t u r e a t t h e warm

(8)

end and ramped t e m p e r a t l l r e a t t h e c o l d end. Other t h e r m a l modes c a n a l s o b e e x e c u t e d .

Another program i n i t i a t e d a t t h i s t i m e i s t h e a u t o m a t i c r e c o r d i n g of t h e d a t a w i t h a n o n - l i n e p r i n t e r t h a t g i v e s t h e sample t e m p e r a t u r e s a t s e l e c t e d t i m e s , t h e sample l e n g t h change ( h e a v e ) and t h e w a t e r volume i n t a k e . The s t a t u s of t h e t e m p e r a t u r e c o n t r o l a t b o t h ends i s a l s o r e c o r d e d . The d a t a a r e s t o r e d on d i s c and i n t h e form of h a r d copy. P r i n t o u t s c a n b e r e q u e s t e d of a l l t h e d a t a a s r e q u i r e d . Graphs c a n a l s o b e r e q u e s t e d a t any t i m e of f r o s t p e n e t r a t i o n , w a t e r i n t a k e , t o t a l heave v a l u e s anrl i c e s e g r e g a t i o n r a t i o s v s t i m e ; i n a d d i t i o n , t h e p a t t e r n of t e m p e r a t u r e c o n t r o l a t b o t h e n d s a s a f u n c t i o n of t i m e i s a l s o a v a i l a b l e i n g r a p h form. When t h e s c r e e n i s n o t u s e d f o r o t h e r p u r p o s e s , t h e c o n t r o l s t a t u s of t h e end t e m p e r a t u r e c a n be d i s p l a y e d . The computer u p d a t e s t h i s i n f o r m a t i o n a t l e a s t e v e r y t h i r t y seconds.

T o t a l Heave and Water I n t a k e Heave Measurements

The i n s t r u m e n t a t i o n f o r b o t h heave and w a t e r measurements a r e s e r v i c e d

by t h e same power s u p p l y . The i n p u t v o l t a g e i s monitored a u t o m a t i c a l l y and a l a r m s a r e t r i g g e r e d i f t h e v a r i a t i o n e x c e e d s t h e r e q u i r e d a c c u r a c y l i m i t s . The d i f f e r e n c e between t h e two v a l u e s of t o t a l h e a v e and w a t e r i n t a k e heave i s a r e c o r d of i n s i t u pore w a t e r heave.

A v i n t a g e g l a s s - c a s e d a n a l y t i c a l b a l a n c e h a s been automated t o p r o v i d e a c c u r a t e measurements of w a t e r i n t a k e by t h e heaving sample. A f o r c e

t r a n s d u c e r was i n s t a l l e d between one end of t h e h o r i z o n t a l b a l a n c e beam and t h e b a s e of t h e b a l a n c e e n c l o s u r e . A v e n t e d w a t e r c o n t a i n e r was hung from t h e o t h e r end of t h e b a l a n c e beam w i t h a v o l u m e t r i c c a p a c i t y of a b o u t 50 cc. A t u b i n g arrangement s u p p l i e s w a t e r from t h e b a l a n c e t o t h e f r o s t c e l l t h r o u g h a p o r o u s p l a t e . V o l t a g e o u t p u t from t h e f o r c e gauge was c a l i b r a t e d i n terms of w a t e r s u p p l y . An a c c u r a c y of

+

0.01 mm of heave was a c h i e v e d which i s e q u i v a l e n t t o 2 0.31 c c i n t a k e of w a t e r f o r t h i s s i z e of sample. The e x t e r n a l w a t e r s u p p l y l e v e l was a d j u s t e d t o s t a y w i t h i n 0 and +2 cm of t h e p o r o u s p l a t e a t t h e end of t h e sample.

Measurements of specimen heave a r e made o v e r t h e e n t i r e f r e e z i n g p e r i o d u s i n g a DCDT mounted between t h e t o p of t h e f r o s t c e l l and t h e heave

t r a n s f e r p i p e ( F i g u r e 1). Measurements a r e a c c u r a t e t o '0.002 mm.

EXPERIMENTAL WSULTS

-

EXAMPLES

With t h e a p p a r a t u s and e x p e r i m e n t a l methods d e s c r i b e d above, t h e measurements of w a t e r i n t a k e and h e a v i n g a r e much more p r e c i s e t h a n was p r e v i o u s l y p o s s i b l e . I c e l e n s growth r a t e changes can b e o b s e r v e d d u r i n g f o r m a t i o n . With t h e X-ray c a p a b i l i t y g i v i n g e x a c t l e n s p o s i t i o n and t h e sample p r o f i l e t e m p e r a t u r e measurements t a k e n a t t h e same t i m e , i t i s

p o s s i b l e t o d e t e r m i n e t h e t e m p e r a t u r e of t h e a c t i v e l y growing f a c e of t h e i c e l e n s .

(9)

An i n t e r e s t i n g p a t t e r n of growth t e m p e r a t u r e d u r i n g r h y t h m i c i c e l e n s i n g emerges from e x p e r i m e n t s . T h i s l e d t o a s s e s s m e n t s of i c e l e n s growth b e h a v i o u r n o t p o s s i b l e p r e v i o u s l y . Some r e s u l t s a r e g i v e n below.

A r e c o r d of c o m p u t e r - c o n t r o l l e d sample end t e m p e r a t u r e s i s g i v e n i n F i g u r e 4 ( a ) . In t h i s e x p e r i m e n t , t h e t e m p e r a t u r e s were d e c r e a s e d i n i n c r e m e n t s of 0.0015°C t o g i v e a t o t a l d r o p of 0.02OC p e r 24 h o u r p e r i o d . F i g u r e 4 ( b ) g i v e s t h e O°C i s o t h e r m p e n e t r a t i o n d u r i n g t h e p e r i o d of ramped t e m p e r a t u r e c o n t r o l shown i n F i g u r e 4 ( a ) . F i g u r e 4 ( c ) g i v e s t h e r e c o r d of t h e t o t a l h e a v e ( i n s i t u w a t e r a n d w a t e r i n t a k e ) measured a s a f u n c t i o n of t i m e , a s w e l l a s t h e h e a v e due t o w a t e r i n t a k e o n l y . The f o u r i c e l e n s e s were formed o v e r t h e t i m e p e r i o d s marked on t h e c u r v e . I n d i c a t e d a l s o a r e t i m e s a t which X-rays were t a k e n .

It may be s e e n t h a t t h e r a t e of t o t a l h e a v e and w a t e r i n t a k e heave go t h r o u g h a r a t e change d u r i n g t h e f o r m a t i o n of t h e i c e l e n s .

I n a d d i t i o n t o a measured heave r a t e c h a n g e , t h e t e m p e r a t u r e a l s o changes. From t h e X-ray which shows t h e l e n s l o c a t i o n a t t h e t i m e of t h e measured t e m p e r a t u r e g r a d i e n t c u r v e ( F i g u r e 4 ( d ) ) , t h e t e m p e r a t u r e a t t h e f a c e of t h e growing i c e l e n s c a n be c a l c u l a t e d . The d a t a i n T a b l e 1 g i v e s s u c h t e m p e r a t u r e c a l c u l a t i o n s f o r l e n s e s 3 and 4. A t t h e t i m e of l e n s i n i t i a t i o n t h e AT below O°C i s less t h a n a t s u b s e q u e n t t i m e s . On t h e o t h e r

hand b o t h t h e t o t a l and i n t a k e w a t e r h e a v e o v e r t h e l e n s f o r m a t i o n p e r i o d i n c r e a s e s t o a maximum t h e n r e d u c e s . T h i s p a t t e r n i s always t h e same and many e x p e r i m e n t s have been c a r r i e d o u t showing h e a v e and l e n s t e m p e r a t u r e w i t h s i m i l a r c h a r a c t e r i s t i c s . A p o s i t i v e p r i n t of t h e X-ray t a k e n when t h e t e m p e r a t u r e g r a d i e n t i n F i g u r e 4 ( d ) was e s t a b l i s h e d i s g i v e n i n F i g u r e 4 ( e ) , X-ray

5.

I n t h i s f i g u r e , a l l t h e p o s i t i v e p r i n t s of X-rays t a k e n d u r i n g t h e f u n c t i o n of l e n s e s 3 and 4 a r e shown. The g r a i n s i z e c h a r a c t e r i s t i c s are g i v e n f o r t h i s s o i l i n Appendix l ( a ) .

TABLE 1. ICE LENS DATA. SOIL M I X NO. 2.

RAMP

RATE -0.02/24 HR. PERIOD.

X r a y No. Lens No.

Lens/O°C

Lens Temp. s e p a r a t i o n Time

O C mm min

.

1 S t a r t of 3

-

0.240 26.08 7,115 2 Midway t h r o u g h 3

-

0.258 27.84 8 , 6 19 3 Near end of 3

-

0.270 29.72 10,009 4 S t a r t of 4

-

0.238 26.55 11,382 5 Middle of 4

-

0.250 27.92 12,816 The h e a v e r e c o r d of a n o t h e r e x p e r i m e n t i s shown i n F i g u r e 5. T h i s i s a d i f f e r e n t s o i l mix, Appendix l ( b ) , from s i m i l a r s o i l m a t e r i a l s . Again t h e t i m e of t h e X-rays are marked on t h e heave t i m e curve. The change i n heave

(10)

r a t e may be n o t e d a g a i n a s t h e l e n s growth p r o g r e s s e s . Table 2 g i v e s t h e t e m p e r a t u r e d a t a . The p a t t e r n of t e m p e r a t u r e changes i s s i m i l a r t o t h a t i n Table 1. The growth t e m p e r a t u r e s a t t h e i c e l e n s c o n t i n u o u s l y r e d u c e s and when a new l e n s i s i n i t i a t e d t h e t e m p e r a t u r e i n c r e a s e s t o g i v e a warmer t e m p e r a t u r e d u r i n g t h e e a r l y s t a g e of growth.

SUMMARY

The p r e c i s i o n of t e m p e r a t u r e measurements and c o n t r o l d u r i n g heaving experiments h a s improved t o t h e p o i n t t h a t changes i n growth r a t e of

ice

d u r i n g rhythmic i c e l e n s f o r m a t i o n c a n be observed. It i s now a l s o p o s s i b l e t o l o c a t e t h e

ice

l e n s e s p r e c i s e l y u s i n g X-rays. Hence, t h e t e m p e r a t u r e of t h e a c t i v e l y growing i c e phase can be determined.

TABLE 2. I C E LENS DATA. SOIL M I X NO. 1.

RAMP

RATE -0.01°C/24 HR. PERIOD

Lens O°C

Lens Temp. s e p a r a t i o n Time

OC mm min

.

X r a y No. Lens No.

S t a r t of 1 Toward end of 1 Middle of 2 S t a r t of 3 Toward end of 3 S t a r t of 4 Toward end of 4 End of 4 S t a r t of

5

Toward end of 5 S t a r t of 6 Middle of 6 S t a r t of 7

(11)

WATER SUPPLY T O SAMPLE HEAVE TRANSFER P I P E

-I

A I R PRESSURE INLET W A R M S I D E TYGON TUBING COOLING L I Q U I D TOP A L U M I N U M COPPER WATER SUPPLY TUBE 57 rnm ( 2 114") URETHANE INSULA Z IG-ZAG WATER

SUPPLY GROOVE POROUS PLATE

- - - - - - . . - - - . - - - THERMISTOR LEADS . . - - - SAMPLE HOLDER I \ I C \ S P I R A L COOLING GROOVE T I O N COOLING L I Q U I D F I G U R E 1 S C H E M A T I C O F F R O S T C E L L MK I1

(12)

L I Q U I D TEMPERATURE BATH NO. 1 ELECTRICAL BATH D I G l T A L VOLTMETER COMPUTER TO BATH NO. 2 OUTPUT S I G N A L f 20 MA F I G U R E 2 S C H E M A T I C O F M O D I F I C A T I O N T O T E M P E R A T U R E C O N T R O L L E R O F H O T P A C K L l Q U I D B A T H C l R C U L A T O R

(13)

1 . H P 1000. MODEL 6 COMPUTER 10. TENNEY CONTROLLED ENV I RONMENTAL CHAMBER 2 . H P 9835 COMPUTER 11. CHAMBER GLASS SECTION FOR OBSERVATION 3 . HP 3455A VOLTMETER AND 3495A SCANNER OF CELL

4 . H P 6942A MULTIPROGRAMMER 12. PH l L l PS X-RAY GENERATOR 5 . VOLTAGE SUPPLY FOR DCDT 13. HOTPACK FOR W A R M S I D E 6 . H P 7245A PLOTTER 14. H O l P A C K FOR COLD SIDE

7 . H P GRAPHICS PRINTER 15. HOTPACK FOR CRYSTALLIZATION I N I T I A T I O N 8. HP 2631 PRINTER 16. H P FLOPPY D I S C DRIVE

9. WATER SUPPLY BALANCE 17. HP FLOPPY SLAVE D I S C

F I G U R E 3

(14)

-1.0 0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0 T I M E , m i n F I G U R E 4 ( a l R A M P F R E E Z I N G M E T H O D . R E C O R D O F R A M P E D S A M P L E E N D T E M P E R A T U R E S A T - 0 . O Z " C 1 2 4 h P E R I O D . E X P E R I M E N T A L P E R I O D 16 0 0 0 M I N U T E S , S O I L M I X N O . 1 T I M E , m i n 6 0 5 0 4 0 E E 3 0 2 0 1 0 F I G U R E 4 1 b l R E C O R D O F O ' C I S O T H E R M P E N E T R A T I O N 7 0 . 1 , 1 1 1 1 1 1 1 1 1 I I I ... DEPTH OF 0 C I S O T H E R M ...

-

... WATER HEAVE I ...

----

TOTAL HEAVE OF X - R A Y ... ...

-

- ... ... 3 ... ... ._.. ... 1 X - ~ ~ Y No. - ... - : & - -

-

-

0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 0 1 4 0 0 0 1 6 0 0 0

(15)

F I G U R E 4 ( c l

(16)

OF THERMISTOR

-

-

-

-

-

0 1 T E M P E R A T U R E . ' C F I G U R E 4 ( d ) E X A M P L E OF T E M P E R A T U R E G R A D l E N l IN S A M P L E ( X - R A Y NO. 5 1

(17)

X - R A Y , NO. 5 4 3 2 1 TIME, min 12 816 11 382 10 009 8 619 7 115 F I G U R E 4 ( e l P O S I T I V E P R I N T S O F A L L X - R A Y S T A K E N D U R I N G A C T I V E F R O S T H E A V I N G I 1 I I -

-

W A T E R H E A V E

- - - -

-

T O T A L H E A V E - - - -

-

- -

-

- - I I I I I I I I I T I M E , i n i n F I G U R E 5 R E C O R D O F T O T A L A N D W A T E R - I N T A K E H E A V E S O I L M I X N O . 2 . R A M P R A T E - 0 . Ol'C124 h P E R I O D

(18)

1 I 1 l l l l l - - - - - - - - - - - - - - - I 1 1 1 1 1 1 1 l I 1 1 1 1 1 1 1 1 I 1 I l l l l L , 0 0 1 0 . 0 1 0 1 1 . 0 G R A I N S I Z E , m m A P P E N D I X A H Y D R O M E T E R A N A L Y S I S O F S O I L M I X N O . 1 I I I I I I I ~

-

- -

-

-

- - -

-

- - -

-

-

I I 1 , I 1 1 1 1 I I 1 1 1 1 1 1 1 - 1 1 1 1 1 1 1 ~ 0 0 1 0 . 0 1 0 . 1 1 . 0 G R A I N S I Z E , r n m A P P E N D I X B H Y D R O M E T E R A N A L Y S I S O F S O I L M I X N O . 2

Figure

TABLE  1.  ICE  LENS  DATA.  SOIL  M I X   NO.  2.
TABLE  2.  I C E   LENS  DATA.  SOIL  M I X   NO.  1.

Références

Documents relatifs

Experimental results on clay and clay/concrete interface at 5°C: (a) Shear stress 502 versus horizontal displacement; (b) Vertical displacement versus horizontal displacement; 503

(ANNs) is used to predict the steelbath temperature in oxygen converter process for the end condition.This model has 11 inputs process variables and one output.The model was tested

The objective of the first stage is achieved; we project to generalize this method for process control (prediction bath temperature and composition of steel in end blow). Poferl

Penin L (2003) Recrutement et maintien des populations de coraux scléractiniaires autour de Moorea, Polynésie française : relations entre les recrues, les juvéniles et les adultes.

Hier werden nicht nur sämtliche Fundorte der Levante, an denen bislang Elfenbeinarbeiten gefunden wurden, vor- gestellt (mit Ausnahme der beiden Fundorte Lachisch und Megiddo, die

It is known that CQ answering under IAR and brave se- mantics is tractable for DL-Lite knowledge bases [Lembo et al., 2015; Bienvenu and Rosati, 2013], and we will show that

We observed that Fgfr3 activation in immature OBs and hypertrophic CCs (Osx-Fgfr3) not only perturbed the hypertrophic cells of the growth plate (thus affecting