Inverse Prediction on the Deformation of a Typical High Loess-filled Foundation during and after Construction— Taking a Key Profile as an Example

Abstract

To better predict the deformation of the high loess-filled foundation, the values of the parameters of each layer in the high loess-filled foundation are obtained using changing modulus-iterative method. Based on the parameters, the deformation of the high loess-filled foundation during construction was calculated using ideal elastoplastic constitutive model and visco-elastoplastic constitutive model. Comparison between predicted and measured results indicates that the values of the parameters are suitable for predicting the deformation of the high loess-filled foundation.

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IOP Conference Series: Earth and Environmental Science
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Inverse Prediction on the Deformation of a Typical High Loess-filled
Foundation during and after Construction— Taking a Key Profile as an
Example
To cite this article: Jiwen Zhang et al 2020 IOP Conf. Ser.: Earth Environ. Sci. 455 012065
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The 6th International Conference on Environmental Science and Civil Engineering
IOP Conf. Series: Earth and Environmental Science 455 (2020) 012065
IOP Publishing
doi:10.1088/1755-1315/455/1/012065
1
Inverse Prediction on the Deformation of a Typical High
Loess-filled Foundation during and after Construction—
Taking a Key Profile as an Example
Jiwen Zhang1,2,3, Jie Cao2,3, Caihui Zhu4 and Xiaosen Kang1*
1 Department of Civil Engineering, Xi’an Jiaotong University, Xian-ning west road
No.28, Xi’an, Shaanxi, 710049, China.
2 China JIKAN Research Institute of Engineering Investigations and Design, Co., Ltd.,
Xi’an, 710043, Shaanxi, China
3 Shaanxi Key Laboratory for the Property and Treatment of Special Soil and Rock,
Xi’an, 710043, Shaanxi, China
4 Xi’an University of Technology, South Jinhua Road five, Xi’an, 710048, Shaanxi,
P.R. China
Email: kangxs@stu.xjtu.edu.cn
Abstract. To better predict the deformation of the high loess-filled foundation, the values of
the parameters of each layer in the high loess-filled foundation are obtained using changing
modulus-iterative method. Based on the parameters, the deformation of the high loess-filled
foundation during construction was calculated using ideal elastoplastic constitutive model and
visco-elastoplastic constitutive model. Comparison between predicted and measured results
indicates that the values of the parameters are suitable for predicting the deformation of the
high loess-filled foundation.
1. Introduction
Yan’an locates in the loess plateau with large numbers of mountains and valleys. This special
topographic feature has prevented the development of local economic. To enlarge the effective living
area for people, a new city was built by excavating the loess from mountains and filling it in valleys.
The new city is a typical large loess-filled foundation in China [1-2]. The project on the loess-filled
foundation has been reviewed, modified, and improved widely many times before construction. Cao et
al.[3] analyzed the free-fild seismic responses based on centrifugal model tests. Du et al.[4] analyzed
the settlement behaviors of the high loess-filled foundation from exhaust conditions. Zhang et al.[5]
studied the ggroundwater monitoring in hilly-gully region. Zhang et al. [6] explored some key
technical issues and engineering practices in the construction of the loess-filled foundation. Zhu et al.
[7] analysed the measurement and distribution of earth pressure of high fill in loess gully. To better
predict the deformation of the high loess-filled foundation, it is necessary to determine the values of
the parameters of each layer in the foundation.
2. Numerical Calculation and Discussion
In the high loess-filled foundation, a typical profile was set as a test area for mointoring deformation
of loess-filled foundation. Some sensors are set in drill hole and test pit including four steps:
excavation of the drill hole and test pit, set of the sensors, backfilling and tamping, and arrangement of

The 6th International Conference on Environmental Science and Civil Engineering
IOP Conf. Series: Earth and Environmental Science 455 (2020) 012065
IOP Publishing
doi:10.1088/1755-1315/455/1/012065
2
data wires. Note that the sensors are set every 5-10m in height during the construction of the
foundation. The diameter, coordiante, and altitude of the drill hole were measured.
The site operation of the loess-filled foundation is shown in figure 1. The original topography of
the loess-filled foundation is shown in figure 2. A three-dimension numerical model of the loess-filled
foundation was formulated according to the “Investigation report on high loess-filled foundation in
Yan’an New City” [8], as shown in figure 3. In the numerical model, the side boundary that is along
the valley is within 200 m, and is fixed in normal direction. The side boundary that is perpendicular to
the valley is the edge of the loess-filled foundation, and is fixed in normal direction. The bottom
boundary is more than 100 meters below the bottom of the valley, and is fixed in all directions, as
shown in figure 4. The solid 45 units are adopted in the numerical model. The grid size of the
numerical model is shown in figure 4. A method called nine steps filling and activation is adopted to
predict the deformation of the loess-filled foundation.
Figure 1. Site
operation of the loess-
filled foundation.
Figure 2. Original
topography of the
valley.
Figure 3. Three-
dimension model and
monitor site.
Figure 4. Grid size of
the numerical model.
2.1. Initial Values of the Model Parameters Obtained from Investigation Report
The initial values of the model parameters are determined according to the investigation report and
research report. The values of these parameters are shown in table 1. The values of the parameters of
the original foundation are the average values of experimental data in the report called “Investigation
report on high loess-filled foundation in Yan’an New City”. The values of the parameters of the loess-
filled foundation are average values of experimental data on compacted loess in the report called
“Research report on settlement prediction and stability of high loess-filled foundation”.
Table 1. Model parameters obtained from investigation report (during construction).
Lithology
γ (kN/m3)
φ (°)
c (kPa)
K(MPa)
G(MPa)
J
22.00
200.00
200.00
15151.52
7812.50
N
19.80
90.00
90.00
18.33
8.46
Q2
18.20
24.00
35.00
15.74
6.44
Q3
15.00
25.00
30.00
14.44
4.81
Treat-layer
20.70
27.00
28.00
18.06
4.71
Layer-1
17.34
24.00
33.48
9.81
4.53
Layer-2
17.34
24.00
33.48
9.81
4.53
Layer-3
17.34
24.00
33.48
9.81
4.53
Layer-4
17.34
24.00
33.48
9.81
4.53
Layer-5
17.34
24.00
33.48
9.81
4.53
Layer-6
17.34
24.00
33.48
9.81
4.53
Layer-7
17.34
24.00
33.48
9.81
4.53
Layer-8
17.34
24.00
33.48
9.81
4.53
Layer-9
17.34
24.00
33.48
9.81
4.53

The 6th International Conference on Environmental Science and Civil Engineering
IOP Conf. Series: Earth and Environmental Science 455 (2020) 012065
IOP Publishing
doi:10.1088/1755-1315/455/1/012065
3
2.2. Values of the Model Parameters Obtained from Inverse Prediction
The values of the parameters suitable for simulating the foundation are obtained via inverse prediction.
During construction, the Mohr-Coulomb criterion is adopted. After construction, the Mohr-Coulomb
and a visco-elastoplastic model are both adopted. The creep of Q3 loess is considered by using visco-
elastoplastic constitutive model, and the creep behaviours of red clay N2b and sandstone J are
neglected by using Mohr-Coulomb criterion. In inverse prediction on the loess-filled foundation
during construction, just the parameters related to deformation are changing, that is, the bulk modulus
and shear modulus greatly affect the deformation.
In inverse prediction on the loess-filled foundation after construction, Maxwell shear modulus GM
and viscosity coefficient ηM are two main parameters in the visco-elastoplastic model. The values of
these parameters obtained by inverse prediction are shown in table 2 and table 3.
Table 2. Model parameters obtained from inverse prediction (during construction).
Lithology
γ(kN/m3)
φ (°)
c (kPa)
K(MPa)
G(MPa)
J
22.00
200.00
200.00
1515.5
7812.5
N
19.80
90.00
90.00
18.3
8.5
Q2
18.20
24.00
35.00
15.7
6.4
Q3
15.00
25.00
30.00
14.4
4.8
Treat-layer
20.70
27.00
28.00
36.8
9.6
Layer-1
17.34
24.00
33.48
19.58
9.04
Layer-2
17.34
24.00
33.48
16.1
7.43
Layer-3
17.34
24.00
33.48
13.5
6.23
Layer-4
17.34
24.00
33.48
11.8
5.45
Layer-5
17.34
24.00
33.48
15.3
7.06
Layer-6
17.34
24.00
33.48
12
5.54
Layer-7
17.34
24.00
33.48
11.1
5.12
Layer-8
17.34
24.00
33.48
10.6
4.89
Layer-9
17.34
24.00
33.48
9.55
4.41
Table 3. Model parameters obtained from inverse prediction (after construction).
Lithology
GM (MPa)
ηM (GPa.h)
GK (MPa)
ηK (GPa.h)
Treat-layer
17.35
404.65
97.35
0.460
Layer-1
21.69
505.80
120.02
0.570
Layer-2
11.15
301.13
69.02
0.408
Layer-3
8.72
253.75
60.34
0.348
Layer-4
7.09
193.96
53.95
0.308
Layer-5
5.30
94.54
60.28
0.265
Layer-6
3.60
83.58
45.37
0.230
Layer-7
3.07
52.95
38.12
0.180
Layer-8
2.35
23.52
17.66
0.117
Layer-9
2.35
23.52
17.66
0.117
2.3. Deformation of the High Loess-filled Foundation
The grid of the loess-filled foundation during construction is shown in figure 5. The deformation of
the high loess-filled foundation was calculated using the model parameters obtained from inverse
prediction during construction (see tables 2 and 3), as shown in figure 6.

The 6th International Conference on Environmental Science and Civil Engineering
IOP Conf. Series: Earth and Environmental Science 455 (2020) 012065
IOP Publishing
doi:10.1088/1755-1315/455/1/012065
4
Figure 5. Grid of loess-filled foundation during construction.
Figure 6. Deformation of the loess-filled foundation during construction.
Figure 7 shows the comparison between the model prediction and the measured deformation. This
indicates that the values of the model parameters are suitable for predicting the high loess-filled
foundation.
(a) Layer-1
(b) Layer-2
(c) Layer-3
(d) Layer-4
(e) Layer-5
(f) Layer-6
(g) Layer-7
(h) Layer-8
(i) Layer-9
(a) Layer-1
(b) Layer-2
(c) Layer-3
(d) Layer-4
(e) Layer-5
(f) Layer-6
(g) Layer-7
(h) Layer-8
(i) Layer-9

The 6th International Conference on Environmental Science and Civil Engineering
IOP Conf. Series: Earth and Environmental Science 455 (2020) 012065
IOP Publishing
doi:10.1088/1755-1315/455/1/012065
5
Figure 7. Comparison between model prediction and measured deformation.
3. Conclusion
The model parameters of each layer in the high loess-filled foundation are determined using changing
modulus-iterative method. Based on the parameters, the deformation of the high loess-filled
foundation during and after construction was calculated using Mohr-Coulomb model and a visco-
elastoplastic constitutive model. Comparison between measured and predicted values indicates that the
values of the model parameters are suitable for predicting the high loess-filled foundation.
Acknowledgement
The authors wish to acknowledge the financial support provided by Science and Technology Co-
ordination and Innovation Project of Shaanxi Province in China (No. 2016KTZDSF03-02), CMEC
2017 Science and Technology Research and Development Fund Project (No. CMEC-KJYF-2017-05).
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[3] Cao J, Zhang JW, Zheng JG, et al. (2018) Free-field seismic response based on centrifugal
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