Liquefaction Susceptibility of an Earth Dam Foundation: A Case Study&nbsp;

doi:10.21203/rs.3.rs-285555/v1

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Liquefaction Susceptibility of an Earth Dam Foundation: A Case Study

https://doi.org/10.21203/rs.3.rs-285555/v1

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Sidi El Barrak earth dam is a compacted earth embankment of height 28 m built in 1999 on a heterogeneous foundation with strong dominance of sandy formations. The dam foundation was subjected to several tests to predict its behavior against the liquefaction risk. Standard penetration test (SPT) results served to evaluate the liquefaction risk in an earthquake occurrence.

This article, firstly, presents an interpretation of data collected from SPT tests. Determination of liquefaction risk resulted from the empirical methods proposed by Seed & Idriss, (1985) and Idriss & Boulanger, (2008). Obtained results by those methods showed that, for different earthquake magnitudes equal to 5.25, 6 and 6.75, the risk of liquefaction exists in the pure sand layer located between the ground surface and 15 m depth of the foundation of the earth dam. An UBC3D-PLM constitutive model was adopted for studying the numerical response of sand layer subjected to an earthquake of acceleration equal 0.2 g to estimate its liquefaction risk. Recorded SPT data and laboratory tests results served for the determination of geotechnical parameters of this model. From numerical predictions it revealed that the liquefaction risk is greater for an earthquake characterized by an acceleration equal 0.2g.

Geology

Standard Penetration Test (SPT)

Earth dam

Liquefaction

Sand

Earthquake

Numerical model

Table 1: Physical characteristics of the sands of the foundation of Sidi El Barrak dam

Due to technical limitations, table 1 is only available as a download in the Supplemental Files section.

Table 2: Values of correction factor (k) for length of drill rods

Length of drill rods (d)	k
> 10 m	1
6 - 10 m	0,95
4 - 6 m	0,85
3 - 4 m	0,75

Table 3: Values of correction factor (k’) for sampling tube

N₁ values	k’
< 15	1,1
15 - 30	1,2
> 30	1,3

Table 4: The level of liquefaction severity

LPI	Iwasaki et al. (1982)	Luna and Frost (1998)	MERM (2003)
LPI = 0	Very low	Little to none	None
0 < LPI < 5	Low	Minor	Low
5 < LPI < 15	High	Moderate	Medium
15 < LPI	Very high	Major	High

Table 5: Computed LPI for PGA = 0.2 g corresponding to Mw = 5.25 and M_sf =2.49, data of SPT4.

Depth (m)	d< 80µm	r_d	(N₁)₆₀	CSR	CRR	FS	Z (m)	H (m)	W (z)	F	W(z)FH
1.72	1	0.986	3.3	0.271	0.191	0.705	0.86	1.72	9.57	0.295	4.852
3.22	1	0.975	11.1	0.267	0.313	1.169	2.47	1.5	8.765	0	0.000
6.22	4	0.952	12	0.261	0.329	1.259	4.72	3	7.64	0	0.000
7.72	5	0.941	2.4	0.258	0.179	0.693	6.97	1.5	6.515	0.307	2.999
9.22	8	0.928	9.3	0.254	0.281	1.104	8.47	1.5	5.765	0	0.000
10.72	2	0.887	12.2	0.243	0.66	2.709	9.97	1.5	5.015	0	0.000
12.22	3	0.847	15.5	0.238	0.39	1.676	11.47	1.5	4.265	0	0.000
										LPI	7.851

Table 6: Computed LPI for PGA = 0.2 g corresponding to M = 6 and M_sf =1.77, data of SPT4).

Depth (m)	d< 80µm	r_d	(N₁)₆₀	CSR	CRR	FS	Z (m)	H (m)	W (z)	F	W(z)FH
1.72	1	0.986	3.3	0.271	0.135	0.498	0.86	1.72	9.57	0.502	8.256
3.22	1	0.975	11.1	0.267	0.222	0.829	2.47	1.5	8.765	0.171	2.244
6.22	4	0.952	12	0.261	0.234	0.895	4.72	3	7.64	0.105	2.401
7.72	5	0.941	2.4	0.258	0.127	0.492	6.97	1.5	6.515	0.508	4.966
9.22	8	0.928	9.3	0.254	0.2	0.785	8.47	1.5	5.765	0.215	1.855
10.72	2	0.887	12.2	0.243	0.474	1.945	9.97	1.5	5.015	0.000	0.000
12.22	3	0.847	15.5	0.238	0.281	1.208	11.47	1.5	4.265	0.000	0.000
										LPI	19.723

Table 7: Computed LPI for PGA = 0.2 g corresponding to M = 6.75 and M_sf =1.31, data of SPT4.

Depth (m)	d< 80µm	r_d	(N₁)₆₀	CSR	CRR	FS	Z (m)	H (m)	W (z)	F	W(z)FH
1.72	1	0.986	3.3	0.271	0.1	0.369	0.86	1.72	9.57	0.631	10.383
3.22	1	0.975	11.1	0.267	0.164	0.613	2.47	1.5	8.765	0.387	5.093
6.22	4	0.952	12	0.261	0.173	0.662	4.72	3	7.64	0.338	7.750
7.72	5	0.941	2.4	0.258	0.094	0.364	6.97	1.5	6.515	0.636	6.215
9.22	8	0.928	9.3	0.254	0.148	0.581	8.47	1.5	5.765	0.419	3.621
10.72	2	0.887	12.2	0.243	0.351	1.441	9.97	1.5	5.015	0.000	0.000
12.22	3	0.847	15.5	0.238	0.208	0.894	11.47	1.5	4.265	0.106	0.678
										LPI	33.740

Table 8: Computed LPI for PGA = 0.2 g corresponding to M = 6 and M_sf =1.77, data of SPT7.

Depth (m)	d< 80µm	r_d	(N₁)₆₀	CSR	CRR	FS	Z (m)	H (m)	W (z)	F	W(z)FH
1.72	0	0.987	2.2	0.128	0.126	0.982	0.860	1.720	9.570	0.018	0.294
3.22	0	0.975	14.3	0.127	0.266	2.098	2.470	1.500	8.765	0.000	0.000
4.72	1	0.964	4.1	0.125	0.143	1.141	3.970	1.500	8.015	0.000	0.000
6.22	2	0.952	5.9	0.134	0.161	1.205	5.470	1.500	7.265	0.000	0.000
9.22	2	0.928	18.1	0.155	0.314	2.028	7.720	3.000	6.140	0.000	0.000
12.22	4.8	0.848	13.4	0.157	0.24	1.533	10.720	3.000	4.640	0.000	0.000
15.22	5	0.768	15.2	0.151	0.259	1.710	13.720	3.000	3.140	0.000	0.000
18.22	4	0.688	15	0.142	0.253	1.778	16.720	3.000	1.640	0.000	0.000
										LPI	0.294

Table 9: Computed LPI for PGA = 0.2 g corresponding to M = 6.75 and M_sf =1.31, data of SPT7

Depth (m)	d< 80µm	r_d	(N₁)₆₀	CSR	CRR	FS	Z (m)	H (m)	W (z)	F	W(z)FH
1.72	0	0.987	2.2	0.128	0.093	0.725	0.860	1.720	9.570	0.275	4.528
3.22	0	0.975	14.3	0.127	0.197	1.554	2.470	1.500	8.765	0.000	0.000
4.72	1	0.964	4.1	0.125	0.106	0.846	3.970	1.500	8.015	0.154	1.852
6.22	2	0.952	5.9	0.134	0.119	0.890	5.470	1.500	7.265	0.110	1.195
9.22	2	0.928	18.1	0.155	0.233	1.505	7.720	3.000	6.140	0.000	0.000
12.22	4.8	0.848	13.4	0.157	0.178	1.137	10.720	3.000	4.640	0.000	0.000
15.22	5	0.768	15.2	0.151	0.192	1.267	13.720	3.000	3.140	0.000	0.000
18.22	4	0.688	15	0.142	0.0187	0.131	16.720	3.000	1.640	0.869	4.73
										LPI	11.848

Table 10: Material properties of sand layers (UBC3D-PLM model):

Due to technical limitations, table 10 is only available as a download in the Supplemental Files section.

Tables1n10.docx

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