Theoretical Analysis on Soft Soil Foundation Long-term Settlement

for Storage Yard Engineering

Wenbin Liu

1,2,3,4

Tianjin Port Engineering Institute Co., Ltd. Of CCCC First harbor engineering Co., Ltd., Tianjin, China

CCCC First Harbor Engineering Company Ltd., Tianjin, China

KeyLaboratory of Port Geotechnical Engineering, Ministry of Communications, PRC, Tianjin, China

Key Laboratory of Port Geotechnical Engineering of Tianjin,Tianjin, China

Keywords: Soft soil foundation, storage yard engineering, long-term settlement, in-site monitoring, theoretical

calculation.

Abstract: This paper analysed the long-term settlement of storage yard engineering located at Tianjin Nanjiang Port.

The long-term settlement was calculated based on “Code for Foundation of Port Engineering”, and the

predicted result is compared with the in-site monitoring data. The comparison results show that the long-

term settlement calculation results based on code should be modified before using for settlement prediction.

The modify factor is 1.1 to 1.3 for Tianjin area.

1 INTRODUCTION

The research on soft soil foundation settlement is a

hot topic and many scholars had done lots of work.

The two dimensional formulas of viscous elastic

BIOT's consolidation was established based on

MERCHANT's model(Tang, 2001). The settlement

development regular was analysed with specification

and one-dimensional consolidation theory(Zhou,

2009). The modulus of compression and

consolidation coefficient was also being

determined(Zhou, 2009). A back analysis on

consolidation coefficient with layer-wise summation

method and Terzaghi's one-dimensional

consolidation theory was proposed(Qin, 2012). The

variation regular of consolidation coefficient was

also analyzed and the prediction model for

calculating consolidation coefficient in different

situations was proposed(Qin, 2012). Hierarchical

structure model was replaced with shark fin figure in

research and analyzed 6 factors affecting long-term

settlement with Delphi and analytic hierarchy

process (AHP) method(Li, 2013).

This paper analyzed the long-term settlement

based storage yard engineering in Tianjin Nanjiang

Port. The long-term settlement was calculated based

on “Code for Foundation of Port Engineering”. The

in-site monitoring results were also used for

verifying the calculation results. The comparison

between calculation results and in-site test data

offers a simple way to optimize the code calculation

results for engineering practice.

2 ENGINEERING CASE

The case used in this paper is storage yard

engineering located at Tianjin Nanjiang port. The

specific parameters of foundation soil are listed in

Table 1. Table 2 shows the parameters of e-p curve

for each soil layers.

The vacuum load is 85 kPa, lasting for 120 days.

The construction load is 20 kPa, lasting for 10 days.

Table 2 Parameters of e-p curve for each soil layers.

Table 1 Parameters of foundation soil.

3 THEORETICAL ANALYSES

The Port engineering foundation calculation system

(2008) is used for calculating the long-term

settlement of this road engineering case. Figure 1

shows the calculation settlement and the final

settlement is 1.902 m.

Figure 1 Final settlement for the storage yard engineering.

The final settlement value according to

theoretical calculation method is 1.902 m, while the

in-site monitoring data shows that the final

settlement is 2.323m, 1.22 times as large as

calculation result. The major reason responding for

that is the calculation model according to theory

method is a one-dimensional consolidation model

and ignores the influence of others dimensions on

settlement. The influence of this assumption on

settlement calculation depends heavily on the soil

properties.

4 THEORY OPTIMIZATION

In order to modify the gap between code calculation

result and in-site test value, a modification factor is

used in predicting long-term settlement. The formula

for calculating final settlement is as follow.

isd

∑

−

∞

2i1i

(1)

Where, symbol S

∞

refers to final settlement of

soft soil foundation; m

is modification factor,

determining by the experiment or the empirical

equation; e

and e

respectively represents the void

ratio of its layer under average design value of self-

weight stress and average design value of final

stress. h

is the thickness of its soil layer.

The modification factor for Tianjin area usually

varies from 1.1 to 1.3.

5 CONCLUSIONS

The long-term settlement according to theoretical

calculation should be modified. The value of

modification factor is affected by the preloading

situation and foundation stiffness. The modification

factor for Tianjin area usually varies from 1.1 to 1.3.

The foundation with higher stiffness and exhibiting

lower preloading value needs a larger value of

modification factor.

ACKNOWLEDGEMENTS

The authors are grateful for the support provided by

Natural Science Foundation of Tianjin

(16JCQNJC07200)

REFERENCES

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2. Zhou J. 2009.Prediction of foundation settlement of a

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2104.

3. Qin Z. H. 2012. Consolidation coefficient inversion of

seawall foundation and prediction of its post

construction settlement based on fractal theory, Rock

and Soil Mechanics, 33(6): 1747-1753.

4. Li S. H. 2013.Analysis of the Influencing Factors of

Post–construction Settlement on the Soft Foundation

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