Field Evidence of Pore Pressure Diffusion in Clayey Soils Prone

to LandslidingBERTI, M., SIMONI, A., 2010

JOURNAL OF GEOPHYSICAL RESEARCH, 115,

報告者：蕭鈺指導老師：倪春發 老師

2010/12/16

OUTLINE

1. Introduction

2. Rocca Pitigliana Test Site

3. Monitoring System

4. Hydrologic Modeling

5. Results and Discussion

6. Conclusions

INTRODUCTION

1. [Dhakal and Sidle, 2004; Iverson, 2000;Rosso et al., 2006; Montgomery and Dietrich , 1994] developed simple, explicit equations with few input parameters

2. [Iverson and Major 1987] first proposed

that a simple model for vertical diffusive propagation can be used to interpret the wet‐season groundwater response in a large earth flow body.

3. [ Baum and Reid 1995] discovered that surface infiltration can saturate the landslide body in just a few days,and that the saturated soil responds rapidly to heavy rainfall.

1. To illustrate the hydrologic behavior of weathered

clayey soils overlying a clay‐shale bedrock.

2. To evaluate the capability of the one‐dimensional (1‐D) linear‐diffusion model.

3. To compare the calibrated hydraulic parameters

with those measured by field and laboratory tests.

4. To compare the performance of linear‐diffusion and different models

ROCCA PITIGLIANA TEST SITE

MONITORING SYSTEM

HYDROLOGIC MODELING

Hydraulic Parameters of the Soil

D ： hydraulic diffusivity

K ： hydraulic conductivity

C ： specific moisture capacity

ψ ： pressure head

Saturated Aquifer

2

D =K L

C T

0 0/satD K C

6 7

2 30

4 5 2

10 ~ 10

10 ~ 10 1

5 10 ~ 10

sat

MAX

K m s

C m

D m s

Linear‐Diffusion Model

ψ ： pressure head

D0 ： Saturated hydraulic diffusivity

α ： slope angle

22

0 2=D cos

t Z

RESULTS and DISCUSSION

CONCLUSIONS

1. The pressure waves advance vertically downward through the fully saturated soil at high speed (the

observed velocity is 200 times greater than the

advective front velocity) and become slower and smoother with depth.

2. The short‐term behavior of the clay cover can be well reproduced using the 1‐D linear‐diffusion model proposed by Iverson [2000].

The model loses its predictive capabilities when applied outside its validity domain or when surface ponding occurs

3. The utility of a linear‐diffusion model in the framework of areal slope stability assessment is rather limited.

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