The effect of pH and electrical conductivity of the soaking fluid on the collapse of a silty clay

Renan F. B. Zanin ^##Corresponding author. E-mail adress: renanzanin@uel.br

Universidade Estadual de Londrina, Departamento de Construção Civil, Londrina, PR, Brazil.

Ana C. C. Padilha

Universidade Estadual de Londrina, Departamento de Construção Civil, Londrina, PR, Brazil.

Flávia G. P. Pelaquim

Universidade Estadual de Londrina, Departamento de Construção Civil, Londrina, PR, Brazil.

Nelcí H. M. Gutierrez

Universidade Estadual de Maringá, Departamento de Engenharia Civil, Maringá, PR, Brazil.

Raquel S. Teixeira

Universidade Estadual de Londrina, Departamento de Construção Civil, Londrina, PR, Brazil.

Declaration of interest

The authors guarantee that there are no conflicts of interest in this research.

Authors’ contributions

Renan Zanin: data curation, formal analysis, investigation, visualization, writing – original draft, writing – review & editing. Ana Padilha: conceptualization, data curation, investigation. Flávia Pelaquim: data curation, formal analysis, writing – review & editing. Nelcí Gutierrez: data curation, writing – original draft. Raquel Teixeira: conceptualization, data curation, supervision, writing – original draft.

Jennings & Knight (1975)Jennings, J.E., & Knight, K. (1975). A guide to construction on or with materials exhibiting additional settlement due to “collapse” of grain structure. In Regional Conference for Africa on Soil Mechanics and Foundation Engineering (Ed.), Proc. 7th Regional Conference for Africa on Soil Mechanics and Foundation Engineering (pp. 99-105). Rotterdam: AA Balkema.		D5333-03 (ASTM, 2003ASTM D5333-03. (2003). Standard test method for measurement of collapse potential of soils. ASTM International, West Conshohocken, PA. https://doi.org/10.1520/D5333-03. https://doi.org/10.1520/D5333-03... )
I	Severity of the problem	I	Severity of the problem
0 – 1%	None	0%	None
1 – 5%	Moderate	0.1 – 2%	Slight
5 – 10%	Problematic	2.1 – 6%	Moderate
10 – 20%	Serious	6.1 – 10%	Moderately Severe
> 20%	Very Serious	> 10%	Severe

Parameters	Before the Test	After the Test
Parameters	Natural	Soaked with Water	Soaked with Leachate	Soaked with Alkaline Solution	Soaked with Acid Solution
pH (H₂O)	5.10	4.50	4.40	6.60	6.00
pH (KCl)	4.40	4.50	4.50	4.80	4.40
∆pH*	-0.70	0.00	0.10	-2.20	-1.60
P (mg/dm³)	1.85	2.75	2.55	771.85	2327.25
Al³⁺ (cmol_c/dm³)	0.12	0.19	0.07	0.14	1.06
H+Al (cmol_c/dm³)	5.76	5.34	5.34	7.20	10.45
Ca²⁺ (cmol_c/dm³)	0.79	0.57	0.91	0.35	0.25
Mg²⁺ (cmol_c/dm³)	0.18	0.16	0.76	0.20	0.20
K⁺ (cmol_c/dm³)	0.12	0.06	2.50	0.10	0.10
CEC (cmol_c/dm³)	6.84	6.13	9.51	7.85	11.00

Condition	Moisture Content (%)		Dry Density (kN/m³)		Void Ratio		Degree of Saturation (%)
Condition	Before	After	Before	After	Before	After	Before	After
No Soaking	28.3	22.1	9.5	10.8	2.15	1.77	39.6	37.4
Soaked with Water	28.4	42.5	10.1	14.9	1.98	0.99	43.2	100.0
Soaked with Leachate	31.6	38.9	12.5	18.9	2.16	1.19	43.8	97.9
Soaked with Alkaline Solution	20.7	30.9	11.0	17.3	1.73	0.75	35.9	100.0
Soaked with Acid Solution	20.7	28.8	10.0	17.0	2.00	0.86	31.1	100.0
Average	25.3	35.3	10.9	17.0	2.0	0.9	38.5	99.5
Standard Deviation	5.5	6.5	1.2	1.6	0.2	0.2	6.1	1.0
CV (%)	21.9	18.4	10.6	9.7	9.0	20.0	16.0	1.0

Condition		Moisture Content (%)		Dry Density (kN/m³)		Void Ratio		Degree of Saturation (%)
Condition		Before	After	Before	After	Before	After	Before	After
Soaked with Water	Soaked at 25 kPa	35.9	37.2	10.2	13.3	1.95	1.24	55.3	90.2
	Soaked at 50 kPa	31.0	37.1	9.6	13.4	2.13	1.23	43.8	90.1
	Soaked at 100 kPa	31.4	38.6	10.0	14.6	1.99	1.02	47.3	100.0
Soaked with Leachate	Soaked at 25 kPa	30.9	37.6	10.4	14.0	1.88	1.10	49.4	100.0
	Soaked at 50 kPa	29.5	38.9	11.1	14.9	1.69	0.97	52.2	100.0
	Soaked at 100 kPa	32.1	40.5	10.3	14.5	1.92	1.06	50.1	100.0
Soaked with Alkaline Solution	Soaked at 25 kPa	18.1	34.2	10.2	15.5	1.93	0.91	29.2	100.0
	Soaked at 50 kPa	20.2	32.8	10.3	16.6	1.91	0.90	31.7	100.0
	Soaked at 100 kPa	20.8	31.2	10.0	15.7	2.00	0.93	31.3	100.0
Soaked with Acid Solution	Soaked at 25 kPa	21.0	33.8	10.0	18.4	2.00	0.64	31.5	100.0
	Soaked at 50 kPa	20.1	34.6	9.9	16.4	2.03	0.87	29.8	100.0
	Soaked at 100 kPa	32.1	40.5	10.3	14.5	1.92	1.06	50.1	100.0
Average		26.9	36.4	10.2	15.2	1.9	1.0	41.8	98.4
Standard Deviation		6.3	3.0	0.4	1.5	0.1	0.2	10.2	3.8
CV (%)		23.3	8.3	3.6	9.7	5.4	16.6	24.4	3.9

Stress of Interest (kPa)	No Soaking		Soaked with Water		Soaked with Leachate		Soaked with Alkaline Solution		Soaked with Acid Solution
Stress of Interest (kPa)	e_0(nat)	e_nat	e_0(soak)	e_soak	e_0(soak)	e_soak	e_0(soak)	e_soak	e_0(soak)	e_soak
25	2.15	2.03	1.98	1.83	2.16	1.85	1.73	1.26	2.00	1.52
50		1.98		1.49		1.68		1.10		1.33
100		1.92		1.31		1.50		0.96		1.12

Conditions		Collapse Index - I (%)	Classification Criteria
Soaking Fluid	Stress of Interest (kPa)	Collapse Index - I (%)	Jennings & Knight (1975)Jennings, J.E., & Knight, K. (1975). A guide to construction on or with materials exhibiting additional settlement due to “collapse” of grain structure. In Regional Conference for Africa on Soil Mechanics and Foundation Engineering (Ed.), Proc. 7th Regional Conference for Africa on Soil Mechanics and Foundation Engineering (pp. 99-105). Rotterdam: AA Balkema.	ASTM (2003)ASTM D5333-03. (2003). Standard test method for measurement of collapse potential of soils. ASTM International, West Conshohocken, PA. https://doi.org/10.1520/D5333-03. https://doi.org/10.1520/D5333-03...
Water	25	1.40	Moderate	Slight
	50	11.98	Serious	Severe
	100	16.80	Serious	Severe
Leachate	25	6.23	Problematic	Moderately Severe
	50	10.34	Serious	Severe
	100	14.63	Serious	Severe
Alkaline Solution	25	14.79	Serious	Severe
	50	19.85	Serious	Severe
	100	24.01	Very Serious	Severe
Acid Solution	25	12.92	Serious	Severe
	50	18.24	Serious	Severe
	100	24.22	Very Serious	Severe

Soaking Stress (kPa)	Soaked with Water		Soaked with Leachate		Soaked with Alkaline Solution		Soaked with Acid Solution
Soaking Stress (kPa)	e_b	e_a	e_b	e_a	e_b	e_a	e_b	e_a
25	1.90	1.85	1.81	1.72	1.88	1.51	1.96	1.53
50	2.08	1.87	1.58	1.42	1.86	1.42	1.96	1.43
100	1.69	1.57	1.74	1.41	1.91	1.32	1.79	1.25

Conditions		Collapse Index - I (%)	Classification Criteria
Soaking Fluid	Soaking Stress (kPa)	Collapse Index - I (%)	Jennings & Knight (1975)Jennings, J.E., & Knight, K. (1975). A guide to construction on or with materials exhibiting additional settlement due to “collapse” of grain structure. In Regional Conference for Africa on Soil Mechanics and Foundation Engineering (Ed.), Proc. 7th Regional Conference for Africa on Soil Mechanics and Foundation Engineering (pp. 99-105). Rotterdam: AA Balkema.	ASTM (2003)ASTM D5333-03. (2003). Standard test method for measurement of collapse potential of soils. ASTM International, West Conshohocken, PA. https://doi.org/10.1520/D5333-03. https://doi.org/10.1520/D5333-03...
Water	25	1.79	Moderate	Slight
	50	6.86	Problematic	Moderately Severe
	100	4.45	Moderate	Moderate
Leachate	25	3.34	Moderate	Moderate
	50	6.24	Problematic	Moderately Severe
	100	11.98	Serious	Severe
Alkaline Solution	25	12.66	Serious	Severe
	50	15.37	Serious	Severe
	100	20.23	Very Serious	Severe
Acid Solution	25	14.45	Serious	Severe
	50	17.77	Serious	Severe
	100	19.54	Serious	Severe

Δ e_{c} = [(\frac{e_{n a t}}{e_{0 (n a t)}}) - (\frac{e_{s o a k}}{e_{0 (s o a k)}})] * e_{0 (a v e r)}

Brasil