D204

Bearing capacity failure of a foundation near the crest of a slope in centrifugal model test
Shanzhi TAO, 〇Pongsakorn WONGCHANA, Thirapong PIPATPONGSA, Yosuke HIGO

1. Introduction

applied to the model until slope failure. Then, theMeyerhof [1] proposed a method for determining theweight blocks on the failed side were removed and theultimate bearing capacity for continuous foundations

centrifuge was restarted to induce failure in anotheron the top of a slope based on foundation failure. Whileslope. If sliding did not occur until 50G, the process

many theories were developed after it [2], experimental

was repeated with an increasing number of blocks.

verification was relatively rare. Thus, a centrifugal

3. Test resultsmodel test was conducted to study its effectiveness.

3.1 First loading

2. Centrifuge test(a) First failure on the right-hand side slope
Fig. 1 Photograph of the slope model
The configuration of the centrifugal model in themodel scale before the first loading is shown in Fig. 1above. It consisted of two slope models with the sameheight (15 cm) and different slope angle (left slope:55°, right slope: 65°). A single strip weight block was(b) Second failure on the right-hand side slope

placed near the top edge of each slope, functioning as aFig. 2 Local toe failures on the right-hand side slope

continuous shallow foundation. The block was 2.7 cm

The slope models remained stable until 38.5G whenhigh and 6 cm wide and had a mass of 3 kg. Its lengtha local toe failure happened on the right slope near thewas 18 cm, smaller than the width of the slope modelglass side (as shown in Fig. 2(a)), followed by another(20 cm), to avoid additional resisting force caused by

local toe failure on the remaining part (Fig. 2(b)). Thesethe soil chamber at both ends. The distance from thewere not bearing capacity failures because the shallow

center of the block to the slope crest was 6.75 cm. Six

foundation did not rotate and the sliding surface was inlaser transducers were arranged to measure thethe front of it. This indicates that foundation failure

displacement of the slope. The material used in this test

cannot occur if the weight of the foundation isis called Hiroshima sand under 80% compaction degree

insufficient, and the slope is too steep.

(optimum density is 1.747g/cm3) with a water content

3.2 Second and third loading°of 8%. It has an internal friction angle 𝜙 = 31.7 andan effective cohesion 𝑐 ′ = 3.8 𝑘𝑃𝑎.
Firstly, steadily increasing centrifugal loading was

As shown in Fig. 3, an additional block was placedon the left slope before the second loading. However,no failure happened until 50G.

𝑁𝛾𝑞 = 4.8 and 𝑁𝑐𝑞 = 4.1, 𝑁𝛾𝑞 = 2 for the left slope
and right slope, respectively. Foundation failure canhappen if the ultimate bearing capacity 𝑞𝑢 is smaller
than the applied load 𝑞 by the shallow foundation.
Fig. 3 Model configuration before the second loading1
qu = c ' N cq +  BN q
2(1)

In the centrifuge test, 𝛾 in the above equation ismultiplied by n (scaling factor) and 𝑞 can becalculated as 𝑞 = 𝑛𝑊/𝐴, where W is the weight of theweight blocks and A is the contact area.
The theoretical predictions are presented in theFig. 4 Model configuration before the third loading

diagram below for the left slope with four weightblocks (2G) and the right slope with one block (8G),
which are significantly smaller than the experimental
results. This could be caused by the additional lateralresistance on the two sides of the slope, which is notconsidered in the classical theory using 2D analysis.

Fig. 5 Foundation failure on the right-hand side slope

Fig. 7 Predictions by Meyerhof’s theory
Fig. 6 Displacement of the left-hand side slope

5. Conclusion

During the third loading, four weight blocks wereA gentle slope with a sufficiently heavy foundation

placed, as shown in Fig. 4. Foundation failure occurred,on the top is more susceptible to foundation failure,accompanied by the rotation of the foundation at 30G

whereas the toe failure dominates in a steep slope.

as shown in Fig. 5. The displacement of the left slope

Meyerhof’s theory on foundation failure is proven to bemeasured by LD1, LD3 and LD5 is illustrated in Fig. 6.

conservative because the slope can withstand a greater

Positive and negative values mean that the target point

load in the centrifuge model than predicted.

is moving toward or away from the laser sensor,Reference

respectively. Slow deformation commenced at 25G.

[1] Meyerhof, G. G (1957). The ultimate bearing capacity

Then, a sudden change happened at 30G for all values,of foundations on slopes. In Proc., 4th Int. Conf. on Soil

indicating the occurrence of foundation failure.

Mechanics and Foundation Engineering, 1: 384-386.

4. Evaluation the theory of Meyerhof[2] Kusakabe, Osamu, Tsutomu Kimura, and Hakuju

The equation suggested by Meyerhof [1] is shown inYamaguchi (1981). Bearing capacity of slopes under strip

Eq. (1), where 𝛾 is the unit weight of the soil and B isloads on the top surfaces. Soils and foundations 21(4): 29-

the width of the foundation. Two coefficients 𝑁𝑐𝑞 and40.

𝑁𝛾𝑞 can be defined by charts [1]. Here, 𝑁𝑐𝑞 = 4.5 ,