Correlation of Permeability Coefficient and Coefficient of Consolidation in Pontianak City’s Soft Soil

DOI:10.31629/jit.v2i2.3891 Abstract Soft soil is a type of soil that is difficult to use in construction because it has a low bearing capacity and slow settlement due to its fine grain size. In statistics, the relationship or correlation between two data can be predicted using mathematical formulas to find out how much the two data can influence each other. Most of the soil on the surface of the city of Pontianak is dominated by soft soil, so it is important to know how much the coefficient of consolidation and coefficient of permeability can influence each other. From the results of the regression and correlation calculations, the relationship between the permeability coefficient and the consolidation coefficient for the combination of original soil and sand mixed soil is y = 674.7x + 0.0003 with a value of r = 0.4834. The relationship between the permeability coefficient and the original soil consolidation coefficient is y = 321.4x + 0.0003 with a value of r = 0.4173. The relationship between the coefficient of permeability and the coefficient of consolidation of the sand mixed soil is y = 1295.5x + 0.0003 with a value of r = 0.7994. from the experimental results, it can be concluded that there is a significant influence between the value of the permeability coefficient and the consolidation coefficient


Introduction
The Foundation of the building is one of the most important parts of construction because every building has been found buried on the ground. Therefore, a planner needs to know the soil properties because they will directly affect the buildings above them.
Soft soil has a low bearing capacity and because of its fine grain size, the time required to achieve maximum settlement due to consolidation becomes slow because the water in the soil pores takes a long time to penetrate the soil layer. In determining the time required for consolidation, the planner will usually bring a sample of the soil to be tested on to the laboratory to be examined for consolidation with an oedometer. The consolidation testing process with an oedometer generally takes a long time, which is approximately 8 days. In contrast to consolidation experiments, permeability experiments generally only take 2 days for laboratory testing [1].
From the issues above, we need a way to determine the relationship/correlation between permeability coefficient and coefficient of consolidation of soft soil in Pontianak so that the relationship between them can be determined with a mathematical function and can be predicted its value just by looking at one of the known data

Previous Research
Previous research related to permeability coefficient and coefficient of consolidation was presented elsewhere [2], founded that there is a relationship between the permeability coefficient tested using the falling head permeability test method and the permeability coefficient obtained from the consolidation experiment. Another research defined the permeability from the holes at Northern Barbados ridge area [3] which was conducted by W. Bruckmann et al (1997). These studies showed that the porosity and permeability of mutually proportional, but in both studies were not described further on how much the relationship between permeability coefficient and coefficient of consolidation as well as a mathematical equation

Soil Definition
Soil is a mineral that comes from the remains of weathering of rocks and in Soil civil engineering plays an important role in construction. Grain interlocking between soils can be affected by carbonates, oxides, and organic matter. The space between the particles can contain water, air, or both. (Das, 1995).

Permeability
Permeability is the ability of a material to pass liquids from the pores of the material. Soil pores are interconnected with each other, so that water can flow from a point with a high energy level to a point with a lower energy level. Generally, for laboratory permeability experiments, there are two methods, falling head, and constant head experimental methods.

Consolidation
Consolidation is a result of soil deformation due to the load above it which results in the release of water from the soil pores and shrinking soil volume due to the decrease in void ratio. From the consolidation experiment, two types of parameters can be obtained are Cc or compression index and Cv or consolidation coefficient.

Regression and Correlation
Regression and correlation analysis shows how the relationship between two or more variables affects each other. The value of an unknown variable will be predicted with a certain accuracy based on previous observations about that variable. The greater the value of the correlation coefficient, the greater the relationship between the variables. To know the interpretation of each value of the correlation coefficient can be seen in Table 1.

Research Location
The research was conducted at the Soil Mechanics Laboratory, Faculty of Engineering, Tanjungpura University, Pontianak, while the sampling locations were in 3 different locations, which are Universitas Tanjungpura, Jalan Karet, and Jalan Perdana, Pontianak, West Kalimantan, as presented in Fig. 1 to Fig. 3 below.

Research Methodology
To simplify research, it is necessary to carry out research stages which include:

Result and Discussion
As presented in Table 2 below, the permeability coefficient and coefficient of consolidation on original soil and sand mixed soil are significantly increasing.

Figure 5. Sand Ratio vs Cv Graph
From the table and graph described above, it can be seen that with the increase in the ratio of sand in the soil, the permeability value will increase and the coefficient of consolidation value will also increase. This happens because the more sand fraction is mixed in the original soil, the grain size distribution will become irregular so that the void value will increase which causes the permeability coefficient value to increase.

Relationship between Permeability Coefficient (k) and Consolidation Coefficient (Cv) Original Soil and Sand Mixed Soil
The relationship between the permeability coefficient and the consolidation coefficient can be seen in Figure 6 below. From the calculation results, it is found that the relationship between the permeability coefficient and the coefficient of consolidation for the combined soil between the original soil and sand mixed soil with a ratio of 10%, 20%, and 30% is y = 674.7x+0.0003 and has a correlation coefficient value of 0.4834, so the relationship between the permeability coefficient and the coefficient of consolidation for the combined soil can be determined as a moderate relationship.

Relationship between Permeability Coefficient (k) and Consolidation Coefficient (Cv) Original Soil.
The relationship between the permeability coefficient and the consolidation coefficient can be seen in Figure 7 below. From the calculation results, it is found that the relationship between the permeability coefficient and the coefficient of consolidation for the original soil is y = 321.4x+0.0003 and has a correlation coefficient value of 0.4173, so the relationship between the permeability coefficient and the coefficient of consolidation for the combined soil can be determined as a moderate relationship.

Relationship between Permeability Coefficient (k) and Consolidation Coefficient (Cv) on sand mixed Soil.
The relationship between the permeability coefficient and the consolidation coefficient can be seen in Figure 8 below. From the calculation results, it is found that the relationship between the permeability coefficient and the coefficient of consolidation for the original soil is y = 1295.5x+0.0003 and has a correlation coefficient value of 0.799, so the relationship between the permeability coefficient and the coefficient of consolidation for the combined soil can be determined as a very strong relationship.

Relationship between Sand Mixture Ratio and Compression Index (Cc) of Sand Mixed Soil.
The relationship between the permeability coefficient and the consolidation coefficient can be seen in Figure 9 below. From the calculation results, it is found that the relationship between the sand mixture ratio and the compression index for sand mixed soil is y =0.1525x+0.2187 and has a correlation coefficient value of 0.18, then the relationship between the coefficient of permeability and the coefficient of consolidation for sand-mixed soil can be determined as a weak relationship.

Conclusion
From these data, several conclusions can be drawn. There is a moderate correlation between the value of the laboratory permeability coefficient (k) and the laboratory consolidation coefficient (Cv) in the combined soil between the original soil and the mixed sand soil with a ratio of 10%, 20%, and 30. % with linear regression equation y = 674.7x + 0.0003 and has a correlation coefficient value of r = 0.4834. There is a moderate correlation between the laboratory permeability coefficient (k) and the laboratory consolidation coefficient (Cv) on the original soil with a linear regression equation y = 321.4x + 0.0003 and has a correlation coefficient value of r = 0.4173. There is a very strong correlation between the value of the coefficient of permeability (k) laboratory to the value of the coefficient of consolidation (Cv) laboratory on a sand mixture with a ratio of 10%, 20%, and 30% with the linear regression equation y = 1295.5x + 0.0003 and has a value of correlation coefficient r = 0.7994. There is no significant relationship between the sand mixing ratio and the value of the compression index (Cc) in a sand-mixed soil. The greater the percentage of the sand mixture in the original soil will increase the value of the permeability coefficient, specific gravity value, and affect the value of the consolidation coefficient.