measure in a caisson the changes in volumetric water content under conditions of saturated/unsaturated flow and to compare the experimental results with.
LA-10263-MS UC-70B issued: January 1985
LA—10263-MS DE85 008913
Validation of the TRACR3D Code for Soil Water Flow Under Saturated/Unsaturated Conditions in Three Experiments
B. Perkins B. Travis G. DePoorter
£
VALIDATION OF THE TRACR3D CODE FOR SOIL WATER FLOW UNDER SATURATED/UNSATURATED CONDITIONS IN THREE EXPERIMENTS by B. Perkins, B. Travis, and G. DePoorter ABSTRACT Validation of the TRACR5D code in a one-dimensional form was obtained for flow of soil water in three experiments. In the first experiment, a pulse of watei entered a crushed-tuff soil and initially moved under conditions of saturated flow quickly followed by unsaturated flow. In the second experiment, steady-state unsaturated flow took place. In the fin;il experiment, two slugs of water entered crushed tuff under field conditions. In all three experiments, experimentally measured data for volumetric water content agreed, within experimental errors, with the volumetric water content predicted by the code simulations. The experiments and simulations indicated the need for accurate knowledge of boundary and initial conditions, amount and duration of moisture input, and relevant material properties as input into the computer code. During the validation experiments, limitations on monitoring of water movement in waste burial sites were also noted.
I. INTRODITTION One of ihc mechanisms for mobilization and transport from landfills is for soil water to leach soluble elements from the waste and the leachale to move either as mass flow with the soil water or through the soil water by diffusion. To predict how well a disposal site may be able to contain toxic materials, simulations of the movement of these waste components are necessary. The TRACR3D computer code (Travis 1984) has been developed at Los Alamos to simulate transport of solutes through unsaturated as well as saturated soils and rock. The model computes wat'T and/or air flow under soil moisture conditions ranging from fully •aturated to completely dry. Material properties can van.' spatially. A variety of boundary and source/sink conditions are possible. The model also simulates
transport of sorbable species. Transport mechanisms include advection. diffusion, and dispersion. Sorption can be either equilibrium or kinetic and saturablc or not. Decay chains and leaching sources arc allowed. The TRACR3D model has been used to study migration of species from underground nuclear explosions, high-level radioactive underground waste storage, and low-level radioactive shallow waste burial. Anv mathematical model, to be useful, must be verified and validated. Verification means comparison with analvtic solutions. A number of verification examples for TRACR3D are given in Travis (1984). Validation means comparison of the model with experimental da'.a. A few validation examples for TRACR3' • arc discussed by Travis (1 984).
Laboratory experiments are usually well controlled but do not allow all length and time scales to be tested. Field experiments allow a wider range of length and lime scales bm are frequenth subject to uncertainly regarding the spatial distribution ot material properties. The Los Alamos caisson experiments allow testing of larger length and time scales than laboratory experiments allow but without the uncertainties of large-scale field experiments. The purpose of ihis report is to describe additional validation of the TRACR3D code. The code calculations are compared with measurements made in both caisson and field experiments for infiltration of water into parlialK saturated soils of crushed Bandeher tuff. These measurements provid' only "ow validation and are part of a series of expe lments which will provide data for validation of both flow and transport in partially saturated, unconsolidated media. II. VALIDATION A. Caisson A Water Pulse The purpose of the first experiment was to measure in a caisson the changes in volumetric water content under conditions of saturated/unsaturated flow and to compare the experimental results with the results predicted using the TRACR3D code.
1. Experimental a. Emplacement. The experiment was run in a 304.8-cm-diameter, 609.6-cm-decp caisson (designated A), which is one of a set of six that surround a central access caisson (Fig. 1). Except for the lop 25 cm, the complete assemblage is below grade. Each experimental caisson is equipped with a bottom drain that extends into the central caisson to allow for measurement of the drainage rat.: (Fig. 2). Before the caisson used in this experiment was filled, the bottom drain was covered with a coarse screen. Approximately 25 cm of gravel was placed over the screen and approximately 25 cm of sand was placed over the gravel. The remainder of the caisson was filled to approximately 10 cm of the top rim with crushed, compacted tuff (Fig. 2). The naturally occurring tuff at Los Alamos was excavated using front-end loaders, crushed by running the loaders over the luff, and then screened bs passing through a 12.7-mm screen. For maximum packing density before filling, the screened tuff was mixed in a cement truck with enough water to produce a uniform moisture of between 10 and 13% by volume in the compacted tuff. The damp tuff was then placed in layers in the caisson, and each layer was compacted with "jumping jacks" to give a layer of from 15 to 20 cm thick. Density measurements indicated that maximum density for packed luff was achieved (DePoorleret al. 1982).
SECTION
PLAN VIEW
CAISSON 304.8 CM DIAM 609.6 CM DEEP
WORK PLATFORM
46 CM DIAM
CLOSELY SPACED PORTS BETWEEN EXPERIMENT AND INSTRUMENT CAISSONS
A-F G
EXPERIMENT CAISSON INSTRUMENT AND ACCESS CAISSON
Fig. 1. Experiment Cluster.
VERTICAL PROFILE OF CAISSON SHOWING ACCESS HOLES
CROSS SECTION SHOWING INSTRUMENT LOCATION
SURFACE
a
C
o
D
o
E NEUTRON MOISTURE PROBE
o
©
o
o
o
o
o
o
o
Fig. 2. Caisson instrumentation location.
COMPACTED CRUSHED TUFF
SAND GRAVEL DRAIN After the caissons were filled, holes were ma Je at the levels shown in Fig. 3 at the position marked D in Fig. 2 b\ driving a5.08-cm-o.d. hollow stainless steel tube horizontalK. Then a 5.08-cm-o.d.. 0.026-cm wall-thickness aluminum tube. — 175 cm 'ong. with an aluminum, welded end cap. was inserted to the end ol the hole. These access tubes were used for inseninga neutron moisture probe. (Because of problems in driving the steel tube, the horizon marked A2 in Fig. 3 was driven only about 0.7 m: therefore, the end of the access tube is at this position.) Tensiomcters were iiserted through augercd holes at the same level as the neutron moisture access tubes. The locatioi of the two tensiometers on each side of each access tube is shown in Fig. 2. at locations
C and E, with a distance of 44 cm between the end of a tensiometer and the end of the access tube.
b. Material Properties of the Fill. After the tensiometers were emplaced. water was continually ponded on the surface to a depth of approximately 4 cm. Soil water content was measured by inserting the probe of a neutron moisture gauge into the end of each access tube at the seven different horizons noted as A8-A2 in Fig. 3. Ponding continued until the moisture measurements as a function of depth indicaleu that the caisson was as near saturation as possible, with a maximum volumetric water content of 34.6%. The caisson was then allowed to drain.
TUFF SURFACE 44 cm A8
76 cm A7 (t)
:
75 cm A6
79 cm
AS O 76 cm A4
76 cm A3 ( 74 cm
Fig. 3. Vertical position of neutron probe access tubes. The malnc potential of the compacted, crushed tuff and related material properties were obtained from experimental measurements made during this period of saturating with water and draining. For further details the reader is referred to Abeele (1984). c. Addition of Water. To ensure that water uniformly penetrated the surface of the tuff in Caisson A, the surface was raked flat at 09:00 on September 22,
1982. Volumetric water content as a function of depth was measured to obtain initial conditions. At 10:30. water was added until the depth of water was approximately 4 in. By 15:15 the water had completely soaked into the tuff, and volumetric water content as a function of depth was again m -asured. The top of the caisson was tightly sealed against further infiltration or evaporation. d. Measu-ements The rate of water outflow from the caisson, volumetric soil moisture, and tension as a function of depth were measured frequently for a period of fi weeks (Tahk I). Figure 4 shows graphically the soil water content changes with time. e. Results. The experimental volumetric soil water content data indicate that approximate^ 1 3 cm >>f water infiltrated. The volumetric water content decreased in amplitude rat' er quickK as it moved downward, and below 400 cm no change in water content could be detected expcrinentally. The data indicate that although movement of soil water could not he detected below - 4 0 0 cm at any lime during the experiment, drainage from the caisson required that soil water was moving below this horizon with flux in equal to flux not in those regions in which no change in soil water content was delected. The (Table 1) data also indicate that the introduction of water at the surface was felt very quickly at 'he bottom of the caisson, with drainage increasing to day 12-13, after which the drainage rate remained approximately constant through day 22. when the experiment was terminated. 2. Code Simulation a. Input Conditions. The basic equations used for the TRACR3D simulations run for the three experiments are given in Travis (1984). in these simulations the code was used in a one-dimensional geometry. For the computer TRACR3D simulations, initial and boundary conditions must be specified, as well as material properties. In tunning the simulation for the pulse experiment, th" initial moisture profile in the tuff fill was determined from the experimental data collected just before addition of the slug. Since the caisson had been saturated during the earlier experiments, the degree of saturation in the sand was assumed as 0.99 and in the gravel 0.05 (Table II). Free-flow (0-pressure) conditions were specified at the bottom of the column, and no flow was allowed through the sides.
TABLE I CHANGE IN SOIL MOISTURE FOR THE ADDITION OF A 13-CM WATER PULSE
Date
Volumetric Moisture (%)
lime
Tensiometer Reading (kPa)
Date
Time
Hole A-8 (44 cm depth) 4.21 4'22 4-23 4/24 g-2" 4/2S 4/24 4/30 10/1 10/4 10/5 10/6 10/X 10/14 10/27 1 i/1
13:45 04:00 15:15 04:10 04:45 04:10
IIX: 30 08:50 04:30 10:00 10:30 04:45 10.00 04:20 1 1:00 04:00 NA
17.7 I7.4
24 1 26.3 24 2 22.5 21.5 21.5 21.2 21.3 20.6 14.X 20.0 14.6 14.1 17.4
I 7 .5
Volumetric Moisture (%)
Tensiometer a Reading (kPa)
Hole A-7 (120 cm depth) 24.0 21.5 7.5 40 10.0 14.0 13.0 14.0 14.0 15.0 16.5 17.0 17.0 18.0 21.0 24.0 26.(1
4/21
13:45
18.1
4/22
04:00
18.6
4/22
15:15
18.6
4/23
04:30
26.4
4/24
09:45
25.8
4/27
09:10
24.1
4/28
08:30
23.5
4/24
08:50
23.1
4/30
09:30
22.9
10/1
10:00
23.0
10/4
10:30
21.5
10/5
09:45
21.0
10/6
10:00
20.7
10/8
09:20
20.2
10/14
1 1:00
19.7
10/27
04:00
19.5
NA
19.2
11/1
24.5 24.5 14.5 21.0 21.0 21.5 7.0 7.0 70 7.0 9.0 9.5 9.5 9.0 12.0 10.0 11.5 10.0 1 1.0 10.5 1 3.0 12.0 13.0 12.0 13.5 12.0 14.0 13.5 16.0 14.0 20.0 18.0 21.0 19.0
TABLE I (cont)
Date
Time
Volumetric Moisture (%)
Tensiometer Reading (kPa)
Date
Time
13:45
18.1
9/22
09:00
18.2
9/22
15:15
1 8.0
9/23
09:30
18.2
9/24
09:45
19. X
9/27
09:10
~>~> ^
9/28
08:30
21.9
25.0 24.5 23.5 23.0 23.5 23.0 21.0 20.0 13.5 13.5
9/21
13:45
19.1
9/22
09:00
19.4
9/22
i 5:15
19.4
9/23
09:30
19.2
9/24
09:45
19.4
9.5 9.0 9.0
9/27
09:10
20.7
9/28
08:30
20.8
9/30
08:50 09:30
21.9
9.0
9/29
08:50
21.1
21.8
8.5 10.0
9/30
09:30
21.6
10/1
10:00
21.4
9.5 9.5 9.5
10/4
10:30
21.6
10.5
10/1
10:00
22.7
10/4
10:30
22.1
10/5
09:45
21.9
10/6
10:00
21.8
10/8
09:20
21.6
10/14
11:00
21.4
10/27
04:00
20.3
NA
20.3
9.5
10/5
09:45
21.!
10/6
10:00
20.9
10/8
09:20
20.8
10/14
11:00
20.3
10/27
04:00
19.6
11/1
NA
19.2
11.0 )r:0 11.0 10.0 12.0 11.5 13.0 12.0 16.0 16.0 17.5
16.0
20.0 19.5 24.0 23.5 24.5 24.0 24.0 23.5 22.0 21.5
8.0 9/29
Tensiometer a Reading (kPa)
Hole A-5 (274 cm depth)
rlole A-6
(195 cm depth) 9/21
Volumetric Moisture (%)
11/1
15.0 15.0 12.5 13.0 11.5 12.0 11.5 12.0 10.5 10.5 10.5 10.5 11.0 10.0 11.0 10.0 12.0 11.0 12.0 12.0 17.0 16.0 18.0 17.0
TABLE I (cont)
Date
Volumetric Moisture (%)
Time
Tensiometer a Reading (kPa)
Date
Hole A-4 (350 cm depth) 9/21
13:45
21.1
9/22
09:00
20.8
9/22
15:15
20.4
9/23
09:30
20.9
9/24
09:45
21.0
9/27
09:10
21.1
9/28
08:30
20.7
9/29
08:50
NA
9/30
09:30
21.1
10/1
10:00
20.7
10/4
10:30
22.0
10/5
09:45
21.6
10/6
10:00
21.7
! 0/3
09:20
21.7
10/14
1 1:00
21.6
10/27 11/1
04:00
21.8
NA
21.3
Time
Volumetric Moisture (%)
Tensiometer Reading (kPa)
Hole A-3 (426 cm depth) 20.0 19.5 19.5 19.5 20.0 20.0 20.0 19.0 20.0 18.0 17.0 16.0 16.0 14.0 14.5 13.0 14.0 13.5 12.5 11.5 10.5 10.0 1 1.0 10.0 10.5 10.0 10.0 11.0 ll.fi
10.0 15.0 13.0 15.0 13.0
9/21
13:45
22.1
9/22
09:00
-)-) •)
9/22
15:15
21.9
9/23
09:30
22.1
9/24
09:45
22.0
9/27
09:10
22.1
9/28
08:30
22.0
9/29
08:50
22.7
9/30
09:30
22.4
10/1
10:00
22.8
10/4
10:30
22.8
10/5
09:45
22.7
10/6
10:00
22.5
10/8
09:20
22.4
10/14
11:00
22.9
10/27
04:00
22.7
11/1
NA
22.4
15.5 14.0 15.5 14.0 15.0 13.5 14.5 13.5 15.0 13.5 14.5 13.5 14.0 13.0 13.5 12.0 13.5 12.5 13.0 12.5 12.0 11.0 12.0 10.5 10.5 10.0 12.0 10.0 11.0 10.0 13.0 12.0 13.0 12.0
TABLE I (cont)
Outflow Date
Time
Volumetric Moisture (%)
Tensiometer Reading (kPa)
Hole A-2 (500 cm depth) 9/21 y/22 9/22 9/23 9/24 9/27 9/28 9/29 9/30 10/1 10/4 10/15 10/d 10/8 10/14 10/27 11/1
NA NA 15:15 09:30 09:45 (»: 10 08:30 08:50 09:30 10:00 10:30 09:45 10:00 09:20 1 1:00 04:00 NA
NA NA
NA NA
26.2 26.2 26.4 26.2 25.S 26.5 25.9 26.5 26.3 26.2 26.2 26.1 26.5 26.2 26.4
10.5 10.5 10.0 11.0 1 1.0 10.5 11.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 !0.0
Date
Time Sample Collected
4/24
10:20
4/28
04:25
4/24
04:30
4/30
04:30
10/1
04:30
10,5
10:35
10/6
10.32
10/8
04:50
10/14
1 1:28
Flow Weight (s) Time (hours) mf/min 11 158 (43 hr) 8 386 (23 hr) 8 507.5 (24 hn 10 262 (24 hr) 12017 (24 hr) 18 818 (23.7 hr) 18 737 (24 hr) 20 336 (25 hr) 20 325 (25.5 hr)
4.32 6.08 5.91 7.13 8.35 13.25 13.01 13.56 13.5
•' Two tensiomelcr readings at one date at the same hori/on indicate data for the two tensiomcters located at that hori/on.
r SURFACE
30 29 28 M0IS1fURE BY VOLW
Ui er. 'Assumed value.
Source:
0.70 0.46 0.38 0.30 0.22 0.17 0.14 0.125 0.09 0.07 0.055 0.045 0.04 0.00 A b e e l c . 1984.
TABLE III MATERIAL PROPERTIES USED IN CODE SIMULATION
Property
Tuff
Sand"
Porosity' Saturated Permeabiht\ (10" m/s) Pore Si/c Index >|/l; (bars)
0.346
0.33
0.45
0.25 0.433 0.04
5.00 1.00 0.03
30.00 10.00 0.005
•'11'sed in this context as complete saturation. ''Assumed value.
10
Grave.
o.o-
-5
-4
-1
-3
DISTANCE FROM SURFACE (M) Fig. 5. I 3-cm pulse. Caisson A (?.] hr).
0.0-5
-4
-3
-2
-1
DISTANCE FROM SURFACE (M) Fig. 6. 13-cm pulse. Caisson A (23.6 hr). II
0.0-
-5
-4 -3 DISTANCE FROM SURFACE (M) Fig. 7. 13-cm pulse. Caisson A (2.0 days).
-4 -3 DISTANCE FROM SURFACE (M) Fig. 8. 13-cm pulse, Caisson A (5.0 days). 12
0.0
-5
-4 -3 -2 DISTANCE FROM SURFACE (M)
Fig. 9. 13-cm pulse. Caisson A (6.0 days).
0.0
r -5
-4 -3 -2 DISTANCE FROM SURFACE (M)
i
-1
Fig. 10. 13-cm pulse, Caisson A (7.0 days). 13
CO -5
-4 -3 -2 DISTANCE FROM SURFACE (M)
~\
Fig. 11. 13-cm pulse. Caisson A (8.0 days).
0.0
r
-4 -3 -2 DISTANCE FROM SI IRFACE (M) Fig. 12. 13-cm pulse. Caisson A (9.1 days). 14
T —1
0.0 -5
-4 -3 -2 DISTANCE FROM SURFACE (M)
-1
Fig. 13. 13-cm pulse, Caisson A (12.0 days).
0.0 -6
-5 -2 DISTANCE FROM SURFACE (M) Fig. 14. 13-cm pulse. Caisson A (i 3.0 days). 15
-5
-4 -3 ~2 DISTANCE FROM SURFACE (M)
-1
Fig. 15. 13-cm pulse, Caisson A (14 1 days).
0.0
i T r -4 -3 -2 DISTANCE FROM SURFACE (M) Fig. 16. 13-cm pule, Caisson A (16.0 days).
16
-1
0.0
I
-6
-4 -3 -2 DISTANCE FROM SURFACE (M)
-1
Fie,. 17. 13-cm pulse. Caisson A (22.1 days).
1.0-T~
0.0 -5
-4 -3 -2 DISTANCE FROM SURFACE (M) Fig. 18. 13-cm pulse. Caisson A (1.2 months).
-1
TABLE V COMPARISON OF EXPERIMENTAL DATA WITH CODE SIMULATION FOR PULSE EXPERIMENT (IN DEGREE OF SATURATION)
Depth Beluw Soil Surface (cm)
no
44
274
195
426
350
500
Date
Time
E
S
E
S
K
S
E
S
E
S
E
S
E
S
9/22 4/22 9/23 9,°4 9/27
09:00 15:15 09:30 09:45 09:10
0.52 0.84 0.76 0.70
0.54 0.53 0.76 0 74 0.70
0.54 0.54 0.7')
08:30 08:50 09:3(1 10-00 10: .30 09:45 10:00 0"-20
0 53 0.52 0.53 0.57 0.64 0.63 0 63 0.63 0 62 0.62 0.6: 0.60 1)60 0.59 0.57
0 53 (I 5.1 0.53 0.63 0.68 0.68 067 0.67 0.66 0.65 0.64 0.64 0.63 0.60 0.56
0.56 0.56 0.55 0.56 0.60 0.60 0.61 0.62 0.66 0.64 063 0.63 0.62 0.1)2 0.59
0.56 0.56 0.56 0.56 0.61 0.65 0.66 0.66 0.66 0.65 0.65 0.65 0.64 0.62 0.59
O.oO 0.58 0.60 0.61 0.61 0.60 NA 0.61 0.60 0.64 0.62 0.63 0.63 0 62 0.63
0.60 0.60 0.60 0.59 0.58 0.58 0.59 0.60 0.62 0.65 0.65 0.65 0.65 0.64 0.60
0.64 0.63 0 64 0.64
9/28 9/29
0.52 0 HO 0.78 (1.71 0.65 0 61 0.61 0.59 0.59 0.57 0 56 0.56 0.55 0.53 0.51
0.64 0.64 0.64 0.64 0.64 0.64
NA 0.75 0.76 0.76 0.76 0.76 0.77 0.75 0.77 0.76 0.76 0.76 0.75 0.76 0.76
0.76 0.75 0 73 0 73 0 73 0 71 0 73 071 0 71 0 71 0 71 0 71 0 74 0.74 0.73
9/30 10/1 10/4 10/5 10/6 10/8 10/14 10/27
i:
0.65 0.6"" 0.62 0.61 Il.b2 0.60 0.57 0 57 0.57
i
09.0.
0.55 0.52
0.68 0.67 066 0.66 062 0.61 060 0.58 0.57 0.56
0.75 0 68 0.67 0.66 065 0.65 0.62 0.61 0.6(1 0 59 0.57 0.54
0.14 0 64 0.66 G.o5 0.66 0.66 0 66 0.65 0.65 0.66 0.66
0 of moisture as snow fell at the site. During Feburary the snow melted. In March --2.5 cm of additional precipitation occurred. The field moisture data indicate the fate of this winter precipitation. Because of low evaporation in the winter and because of the flat terrain, most of the precipitation infiltrated into the 30 cm of top soil. Because of the soil/gravel interface, buildup of soil water occurred in the topsoil until the potential at the interfaces became the same and a slug of water entered the cobble and moved downward into the underlying crushed tuff fill. The data indicate that at the top of the crushed tuff two "slugs'" of water entered, creating a physical situaticn in the field similar to the experiment run earlier in caisson A. Integration of the "before" and "after" water content in the crushed tuff indicates that approximately 8 cm of water entered the luff in a fairly short interval before February 23. 1983 and another 2 cm slug of water just before March 28. 1983. Significant evaporation from the crushed tuff is prevented by the upper cobble/gravel cover. During the rest o r the year, despite additional precipitation, moisture losses from cvapotranspiration processes prevented significant buildup and "breakthrough" at the topsoil/gravcl interface. 19
0.0
I
-6
i
-3
-4 -3 -1 -2 DISTANCE FROM SURFACE (M) Fig. 19. 200 ml/min inflow, 45% initial saturation (18.5 days).
T 30 cm SOIL 30 cm GRAVEL 61 cm COBBLE
220 cm CRUSHED TUFF
ORIGINAL BANDELIER TUFF Fig. 20. Field experiment profile. 20
TABLE VII MEASURED VOLUMETRIC MOISTURE FOR THE FIELD PULSE EXPERIMENT (1983) Centimeters From Soil Surface
1/11
1/17
2/11 2/15 2/23 2/25
22.2 42.2 62.2 82.2 102.2 122.2 142.2 162.2 182.2 202.2 222.2 242.2 262.2 282.2 302.2 322.2 342.2
22.3 10.7 4.8 3.5 3.7 6.8 8.9 6.7 6.0 6.3 7.1 7.0 7.0 7.1 7.4 8.5 9.4
21.7 10.8 4.9 3.5 3.6 6.3 9.2 6.8 6.0 6.3 6.8 7.1 7.0 7.1 7.4 8.7 9.7
NA 11.7 4.9 3.2 3.4 6.0 10.4 7.6 6.1 6.4 6.8 7.2 7.1 7.2 7.5 8.6 9.2
3/1
3/7
3/21 3/28 4/22 6/22 8/17 10/18 ll/3(
25.7 36.0 35.0 34.2 33.4 13.9 31.1 32.6 11.7 14.1 15.0 12.4 12.5 12.9 8.1 13.2 5.0 5.6 5.9 5.2 5.0 5.8 4.8 5.1 4.1 3.5 4.4 4.2 3.8 4.4 3.9 3.9 4.1 3.4 4.2 3.9 4.1 3.9 4.8 3.9 6.0 9.4 9.5 8.6 8.4 S.4 13.7 8.2 10.7 25.6 25.2 22.1 20.0 20.3 21.9 20.0 8.2 22.6 22.6 20.9 19.4 19.1 20.1 20.0 6.3 12.5 16.1 16.6 16.1 16.1 16.7 17.2 6.5 6.8 8.0 9.9 12.5 13.0 12.6 15.4 7.0 7.0 6.8 7.2 8.2 8.8 8.1 12.1 7.1 7.0 7.1 7.1 7.1 7.1 7.7 7.3 7.0 6.8 7.1 . 7.0 7.1 7.2 7.1 6.8 7.2 7.2 7.1 7.3 7.2 7.2 7.3 7.2 7.6 7.6 7.6 7.8 7.8 7.5 8.2 7.4 8.8 8.6 8.7 8.7 8.6 8.8 8.8 8.5 9.7 9.6 9.7 9.6 9.6 9.9 9.5 9.5
c. Experimental Results. Figure 21 indicates the downward movement of the volumetric water content pulses and the corresponding decrease in amplitude. The changes in soil moisture appear to be "damped" completely by 160 cm below the top of the crushed tuff. The general behavior of the pulses is similar to that observed in caisson A and modeled in the first TRACR3D simulation. However, because of the initial low moisture levels and slightly smaller pulse inputs, the volumetric soil water content pulse movement is much slower, and complete damping (defined as no detectable change in volumetric water content) occurs at a higher horizon. Because the crushed-tuff fill is underlain by the undisturbed Bandelier tuff upon which the experiment was emplaced, interface effects below the crushed tuff may also be present. 2. Code Simulation a. Input Condition A TRACR3D computer simulation was run using the inputs and conditions given in Table VIII. The same mater'ai properties for
NA 5.7 3.6 3.4 3.9 10.7 17.2 16.9 15.3 14.0 12.1 9.3 7.2 7.2 7.9 8.5 9.3
7.4 6.7 4.1 3.4 3.9 8.7 16.1 15.8 14.8 13.9 12.2 9.9 8.0 7.3 7.6 8.5 9.0
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the tuff were used as were used in the caisson simulations, with one exception—the initial dry conditions in the crushed tuff prevented as great a compaction as in the wetter caisson fill and thus 40% was used for saturation. b. Output. The results of the field simulations are shown as the smooth curves in Figs. 22-29. 3. Comparison Code/Field Measurements The experimentally determined data points are included as the dots in Figs. 23-29. The experimental data are also compared with the simulations.in Table IX. As can be seen, the field and simulation agreement are not as close as in the caisson A pulse experiment. Considering the unknown material properties of the field fill and probably greater heterogeneity of the fill, the simulation results are in good agreement. The "damping" point found in the simulation (compare Fig. 22 with Fig. 29) at 160 cm is the same as was found experimentally. Factors affecting the field measurements and code simulations will be discussed in more detail in the next section.
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