Investigation of the discharge performance in infiltration wells based on several soil subgrade models

Heavy precipitation would result in hydrometeorological disasters such as landslides and floods. In general, disasters cause hazardous situations and property loss. Infiltration wells are water and soil conservation techniques that can reduce surface runoff and increase infiltration to mitigate the effects of hydrometeorological disasters. However, evaluations of geotechnical properties have not yet jointly or actively considered these environmental developments. This paper aims to analyse the wide range of soil types against several diameters and depths of the holes. The variation in soil varied from type 1 to 6, containing different properties and consistencies. The holes diameter used are 0.4m, 0.5m, 0.6m, 0.7m, and 0.8m, associated with several depths; 0.5m, 0.75m, 1m, 1.25, and 1.5m. The analysis was conducted with Geostudio SEEP-W in different model variations to obtain the well’s discharge value. The result shows that all the depth depicts similar behaviour of the discharge well. The sand model has the highest value of all categories, with the second place being the sand-clay layer model. In contrast, the clay simulation generates the lowest value of this research. This output offers a strong recommendation between infiltration well structure and soil parameters, which show sand is the most required property to increase the performance of hole infiltration.


Introduction
Much precipitation could result in hydrometeorological disasters like flooding and landslides.Several studies on landslide analysis were conducted in Indonesia [1], [2].Generally, disasters result in dangerous circumstances and property destruction.Based on Situmorang (2021), precipitation is a determining factor in flood analysis.Moreover, runoff management is the greatest obstacle in every major city.Infiltration wells have been established in a specific system to mitigate discharge increases.[3]- [5] A lot of infiltration is well designed to decrease surface runoff that induces flood.According to Scopus database research, the keyword "infiltration well" has the highest value in Indonesia.The top country has developed research on infiltration wells, and the area is presented in Figure 1.This picture describes Indonesia reaching the maximum value of 39.7%, and the lowest is Finland, with 1.7%.The example of a research topic in an infiltration hole was analysed in Palembang, Bangka and Padang for Regarding the soil properties aspect in infiltration analysis, the evaluations of geotechnical properties have not yet been jointly or actively considered.Whereas, Significant correlations between infiltration rate and soil structural properties have been established based on Basset (2023).This condition requires a substantial number of in-situ and field experiments to evaluate the effects of soil structure on water infiltration under the influence of various land uses and soil management practices.In addition, According to Wei (2022), Initial soil moisture content has the greatest impact on the relationship between the rate of infiltration and soil moisture content; the greater the initial moisture content of the soil, the lower the initial infiltration rate, the more rapidly the infiltration rate reduces in soil moisture, and the lower the "relative stable infiltration rate" during the infiltration process.[15]- [17] This study aims to examine several soil properties with varied depths and diameters of the well infiltration.The discharge capacity was analysed based on appropriate methods and variation.This paper is expected to offer a general recommendation of infiltration hole performance based on numerous soil subgrades.

Methods
This paper utilizes a wide type of soil model and well geometries.All the analysis is conducted by GeoStudio software.

Soil properties
The parameters of soil were modelled in 6 types which have depicted in Table 1.The properties of soil were modelled in 6 types depicted in Table 1.The input properties are unit weight (γ), cohesion (c), friction angle (φ), poisson ratio (v) hydraulic conductivity (kx/ky), elasticity (E), and water content (w).The data was obtained from various soil consistency representing the clay and sand properties [18].

Analysis of SWEEP/W to generate water flux
Geostudio SWEEP/W analysed the model in different models.The diameter and depth vary the geometry of the hole.The depth types are 0.5m, 0.75m, 1m, 1.25, and 1.5m, and the diameters are 0.4m, 0.5m, 0.6m, 0.7m, and 0.8m.All the models represent different soil properties (the input is based on Table 1) and different depths and diameters of the well.As the general model of the Geostudio SWEEP/W, the detailed picture is shown in Figure 2.

Analysis of discharge behavior
The input of Equation One obtained the discharge calculation.The examination was calculated by the water flux times to the area of wells.
Where Q is the discharge capacity, v means the water flux and A is area of the infiltration well.

Results and Discussion
The result of this research has provided as follows:

Discharge output from SWEEP/W
Initially, the output of Geostudio SEEP/W is the water flux value.To change this condition for discharge condition, equation 1 is analyzed to generate the new value.The discharge capacity in the depth of hole version of 0.5m has presented in Table 2.
According to Table 2, the discharge value varied from 10 -6 to 10 -10 .The larger diameter of the hole, the greater the discharge will be.This condition is suitable because the diameter of the infiltration well is connected to the discharge capacity.Moreover, this table shows that the soil properties have different numbers of discharge results.Soil type 2 has the highest value; contrastingly, the lowest is in the soil 5 types.The other perspective of this output has shown in Figure 3.
Figure 3 illustrates the discharge value from all categories.The highest value is in Soil 2 properties, and the second rank is Soil 6 types with almost similar discharge capacity trends.These conditions also describe the same behaviour toward the diameters of the hole.The larger diameter of the hole, the more Depth 0-2.5mDiameter Depth of the well Depth under 2.5m significant discharge will be.Although it was affected by the soil properties, the diameter played a significant role in discharge value.
It is similar to previous findings of other research that the three main affecting parameters are water depth, film hole diameter, and soil texture for infiltration area [19].Moreover, based on Lolom [20], the most outstanding result for infiltration technology efficiency in PVC pipes with different hole diameters is 70.6%, which raises the field permeability to 95%.Another finding about diameter was that side infiltration volume per unit film hole area and cumulative infiltration volume per unit film hole area decreased with increasing film hole diameter of free infiltration for muddy water [21].The critical factor of this result is diameter and depth.Yanwei [22] describes the average values for Well diameters and Space between the good power function indicators are 2.6 and 2.5, respectively, indicating that there is little difference between them, which is related to the infiltration volume reduction.Meanwhile, Devianti's research presents results indicating that the total volume of surface discharge can be reduced by 26.50% in experimental plots with infiltration holes in the same diameters and depth [23].Furthermore, Zhangs [24] demonstrated that the infiltration holes at various depths boosted daily soil evaporation for the first 26 days under the high starting soil water content, thereafter it declined.
The result of this study claims that the various soil type induces different discharge capacity.The diameters and depth of the well offer several outputs.Consequently, the utilization of good infiltration should consider the soil subgrade of the area, as well as the structure's depth and diameter, although this system is suitable to prevent surface runoff.Moreover, watershed levels may decrease discharge by 7.514% to 27.545% using model 1 infiltration holes and bio pore combination in the Batang Kuranji catchment area.Moreover, based on the total sustainability rating of the drainage system, another study suggests drainage channels, infiltration wells, and bio pore absorption holes as the optimum management strategy [25], [26].

Conclusions
In general, the output indicates that all depths demonstrate similar discharge well behaviour.The sand model has the highest value in all categories, followed by the sand-clay layer model.In contrast, the simulation of clay contributes a small amount to this research.In summary, the variation of the well infiltration size, such as diameter, depth, and soil subgrade, provides discharge capacity performance.The smaller the diameter, the minimum discharge of the well.In addition, the deeper the wall's depth, the larger the discharge.This output strongly recommends infiltration well structure and soil parameters, suggesting that sand is the most necessary property to improve well infiltration performance.

Figure 1 .
Figure 1.Publication in Scopus related to infiltration well based on countries

Figure 2 .
Figure 2. Input model from SWEEP/W software

Figure 3 .
Figure 3. Water discharge output from well depth in 0.5m

Figure 4
presents the well's depth at 0.5m, Figure5is 0.75m, Figure6at 1.0m, Figure7at 1.25m, and last Figure8depicts 1.5m.All the trend illustrates a similar style with the value of discharge.Soil 2 has the highest presentation of all categories, which Soil 1, 3, 4, and 5 presents a tight range of the discharge.Meanwhile, Soil 6 has a moderate discharge value with a second range of the value.Regarding the diameter of the well, the smaller size of the well, the minimum discharge will be in all the soil types, although the less different gaps in Soil parameter 1, 3, 4 and 5.

Table 1 .
Soil properties for input model parameter

Table 2 .
The discharge result from depth hole 0.5m.