Hydraulic Resistance Analysis Based on Cohesive Strength and Toughness of Synthetic Polymerized Rubber Gel Used as Water-Leakage Repair Material for Concrete Structures

Abstract

As construction in urban centers increases internationally, many concrete infrastructures are being built at 100 m or more underground, and the influence of groundwater on these facilities is also increasing. Accordingly, the importance of waterproofing and leak-proofing technology for securing long-term durability and safety of underground concrete facilities has been greatly emphasized. The most important required performance of such leak repair technology is to withstand structural behavior and groundwater pressure well. Currently, as a leak repair material for underground concrete facilities, a synthetic rubber-based polymer rubber gel with adhesive flexibility is used internationally. However, quantitative data on how deep the material can perform underground are lacking. In general, the water pressure resistance evaluation of leak repair materials only checks whether it withstands the water pressure of 30 m (0.3 MPa) underground. Therefore, in this study, the toughness of the synthetic rubber polymerized gel (SPRG) leak repair material was calculated using three factors: viscosity, cohesive strength (adhesion strength), and elongation, and an analysis method that can be replaced with water pressure resistance was proposed. In addition, in the correlation between toughness and underground water pressure, it was possible to find out the thickness of the leak repair material used by the underground depth. As a result, it was possible to know the required thickness of the leak repair material according to the depth of the structure to be built underground.

1. Introduction

In the case of concrete structures constructed underground, major problems have been raised in the safety and usability of the structures due to dry shrinkage cracks at the initial stage of curing and leakage from member joints and cold joints [1]. Groundwater flowing into the interior along these cracks and joints increases maintenance costs due to discharge [2], and especially, water passing through concrete structures corrodes buried reinforcing bars and steel frames, thereby reducing the durability and safety of structures [3]. To overcome this situation, ISO TR 16475 [4] and ISO TS 16774 [5] stipulate standard guidelines for leak crack repair and test methods for repair material performance evaluation. Therefore, repair materials and methods are needed to prevent leakage from entering the concrete structure and indoor space at the initial stage [6,7]. Recently, a waterproof layer reforming injection method using a synthetic rubber-based polymer gel (hereinafter referred to as SPRG) leak repair material has been developed and is being used internationally [7,8]. The biggest reason why SPRG is used as a leak-crack repair material is that it is a non-hardening gel, and it does not break or tear even in cracks and joint behavior, and it has the characteristic of continuously attaching to the wet surface [9,10]. In other words, when high-viscosity SPRG is injected into leaky cracks or gaps in the joint, it has been evaluated because it has excellent resistance to repeated behavior and high pressure. Therefore, it is very important to always maintain high viscosity in order for SPRG to have continuous hydraulic resistance [10,11]. However, for on-site quality control of this material and method, the standard for the appropriate amount of SPRG filling (usage) or the appropriate thickness according to the depth of the underground has not yet been established [12,13]. Therefore, it is necessary to measure the injection amount and thickness of the repair material for leak repair design according to the depth of the underground structure.

Therefore, it is necessary to check the correlation between the viscosity of the SPRG and the water pressure resistance, which responds to the behavior of concrete members in cracks or joints, contraction, and expansion due to temperature, and subsidence of the ground. When SPRG is injected along the leak path of cracks and joints, the material repels water while filling the voids. In this state, when the pressure of groundwater acts, the water inflow is blocked by the hydraulic resistance of the SPRG [14,15]. At this time, the water pressure resistance or hydraulic resistance largely depends on the viscosity or cohesiveness (cohesive force) of the SPRG. The higher the viscosity, the greater the cohesive force and hydraulic resistance, and the lower the viscosity, the weaker the cohesive force and hydraulic resistance [16]. Therefore, it is necessary to quantitatively evaluate the correlation with the underground water pressure according to the viscosity or cohesiveness of the SPRG. Therefore, in this study, a theoretical analysis was conducted to confirm the interconnection of viscosity, cohesiveness, toughness, and hydraulic resistance of SPRG. ‘Viscosity’ is a quantity that indicates the difficulty of fluid flow, and is defined as the degree of stickiness or internal resistance when flowing. Here, the internal resistance refers to the chemical bonding force between atoms or molecules constituting the material, and it can be expressed as ‘cohesiveness (cohesive force)’, which is the interaction between molecules [17]. Here, ‘cohesiveness’ can also be defined as the cohesive strength of a solid or liquid substance to adhere to another substrate or to resist applied energy and maintain adhesion until destruction [18,19]. This ‘cohesiveness’ for a solid or liquid to maintain its shape due to intermolecular attraction can also be defined as ‘toughness’ of a substance. ‘Water pressure’ acts as a force to destroy the internal resistance (water pressure resistance) of the waterproofing material in the waterproofing field [20,21]. Therefore, the waterproofing material must have energy to resist water pressure (water pressure resistance) and secure sufficient ‘toughness’ of the material, which can in turn be interpreted as ‘hydraulic resistance’. Based on this theory, in this study, the interconnection of ‘cohesive strength’, ‘toughness’, and ‘hydraulic resistance’ can be equally applied as N/mm² in the unit of measurement of force.

Accordingly, as a previously published study, Jong-Yong Lee proposed the possibility to find ‘toughness’ in the stress-strain relationship of SPRG and to judge the toughness as hydraulic resistance [22,23]. Based on this, in this study, ‘cohesive force’ and ‘toughness’ were calculated according to the temperature at each depth in the underground for SPRG of high, medium, and low viscosity. Again, the correlation between toughness and water pressure resistance is obtained, and the appropriate thickness for each viscosity of SPRG that can resist changes in water pressure according to the depth of the ground is presented.

2. Analysis and Experimental Methods of Correlating Toughness and Hydraulic Resistance

2.1. Analysis of the Relationship between Viscosity, Cohesive Strength, Toughness, and Hydraulic Resistance

2.1.1. Cohesive Strength

The polymer material used in this study, SPRG, maintains the cohesive force between molecules in a stable state, and when an external force is applied, the intermolecular cohesive force acts as a stress that resists the external force [24,25]. This cohesive force is engineeringly defined as cohesive strength with a substrate [26,27]. Therefore, the cohesive strength can be calculated as in Equation (1) because the value of the adhesive strength measured according to the test method presented in 2.3 can be used.

$${\tau }_a=\frac{P_{max}}{1600}$$

(1)

where${\tau }_a$ is the Cohesive Strength (N/mm²) and$P_{max}$ is the Maximum Load (Force) (N).

2.1.2. Elongation

Elongation can be obtained by following the test method presented in Section 2.3 along with measuring the adhesive strength. Therefore, in parallel with the cohesive strength measurement in Section 2.1.1, the maximum elongation of the SPRG can be calculated as in Equation (2).

$${\epsilon }_a=\frac{\Delta L}{L_0}\times 100$$

(2)

where${\epsilon }_a$ is the Elongation between attachments at break (%),$L_0$ is the Distance between attachments (mm), and$\Delta L$ is the Elongation at break (mm).

2.1.3. Toughness

Toughness can be calculated according to Equation (3) using the cohesive strength and elongation obtained in Equations (1) and (2) above.

$${{\displaystyle \int }}_0^{\epsilon f}\sigma d\epsilon$$

(3)

where is the $\epsilon$ = strain,$\epsilon f$ is the strain at break, and$\sigma$ is the Stress (MPa, N/mm²).

The toughness value calculated according to the above formula can be confirmed as the total area under the stress-strain curve confirmed in the cohesive strength (adhesion strength) measurement as shown in Figure 1, and the area of the graph can be defined as the toughness value.

2.1.4. Estimation of Water Pressure Response Performance

Toughness can be interpreted as ‘energy that resists damage without being destroyed by water pressure’ according to the definition of ‘energy required for destruction’. Moreover, since the unit of toughness and water pressure is ‘force acting per unit area’, the same unit is used, so there is no problem in commonly used analysis, and toughness and water pressure are regarded as the same [18]. This relation between toughness and hydrostatic pressure is summarized in Figure 2 below.

When the atmospheric pressure is 1 atm, it is 1.01 × 10⁵ Pa, which can be converted into units of 0.1 MPa (N/mm²). In general, the water pressure at 10 m underground is 10 tonf/m² = 0.1 MPa = 0.1 N/ mm², which can be converted into units. If this is journalized in units of 1 m, the water pressure of 1 m underground = 1 tonf/m² = 0.01 MPa = 0.01 N/mm² is converted into units.

For example, in the case of 30 m underground, the water pressure acting can be converted to 0.3 N/mm².

2.2. Materials and Equipment Used in Experiments and Analysis

In this study, three viscosity types of SPRG were used. The material composition ratio (%) and viscosity (cP) of each type are shown in

Table 1. Composition and viscosity of SPRG.

		Type A	Type B	Type C
Composition	Waste oil	24%	22.5%	20%
	Waste rubber	6%	7.5%	10%
	Asphalt	35%	35%	35%
	Tackifier	10%	10%	10%
	Asphalt modifier	5%	5%	5%
	Filler	20%	20%	20%
	Total	100%	100%	100%
Viscosity		1.8~2.1 million cP	3.5~3.8 million cP	5.0~5.3 million cP
Remark		Low viscosity	Medium viscosity	High viscosity

. Figure 3 shows the photos of the SPRG material samples that were tested in this study.

2.3. Test Method

To measure the cohesive strength (adhesion strength) of viscous materials, as shown in Figure 4, the ‘tensile adhesion test method’ proposed by Jong-Yong Lee [8] was used.

In the case of manufacturing multiple specimens by simulating concrete cracks in manufacturing the test base, in order to obtain the consistency of the specimen with a homogeneous surface state, a 40 × 40 × 10 mm size iron attachment was used as specified in ASTM D 2651 and ASTM D 7234. The two were replaced with the substrate, and the gap was defined as the concrete crack width or joint width.

The experimental conditions are shown in

Table 2. Test conditions.

Test Condition	Temperature	Thickness	Test Speed
	5 °C, 10 °C, 20 °C	2 mm, 10 mm	20 mm/min

. Considering the temperature change environment in the underground space [10], the cohesive strength is measured at 5 °C, 10 °C, and 20 °C. The leakage crack width (injection material thickness) is assumed to be 2 mm to 10 mm considering the general behavior of underground concrete [10], and after fixing the spacing between attachments to 2 mm and 10 mm, SPRG is injected and cured. cured specimen is installed on to the universal testing machine (UTM), whereby tensile force is applied at a rate of 20 mm/min in the vertical direction, and maximum load and displacement values are recorded and the raw data from the UTM program are extracted and measured values using Formulas (1), (2), and (3) were calculated. In this study, all test data were measured five times for each condition, and among them, three values excluding the maximum and minimum values were used for analysis. Refer to Figure 5 for an illustration of the UTM testing chamber and the apparatus for material testing.

3. Analysis and Consideration of Result

3.1. Cohesive Strength and Toughness of 2 mm Thickness

The results of measuring the cohesive strength and toughness under the temperature conditions of 5 °C, 10 °C, and 20 °C on a 2 mm thick specimen for each SPRG viscosity type are shown in Figure 6,

Table 3. Measurement result based on specimen types (2 mm thickness).

Specimen Types	Temperature (°C)	Cohesive Strength [N/mm2]	Avg. Cohesive Strength [N/mm2]	Elongation [%]	Average Elongation [%]	Toughness [N/mm2]	Average Toughness [N/mm2]
Type A	5	0.0170	0.0195	1297	1141	0.0138	0.0123
		0.0175		1002		0.0110
		0.0242		1125		0.0122
	10	0.012	0.0115	1221	1400	0.0105	0.0117
		0.0097		1571		0.0119
		0.0128		1398		0.0129
	20	0.0125	0.0136	106	695	0.0035	0.0033
		0.0134		849		0.0038
		0.0148		1129		0.0026
Type B	5	0.0236	0.0213	1589	1409	0.0298	0.0294
		0.0169		2013		0.0359
		0.0237		626		0.0226
	10	0.0194	0.0251	1358	1369	0.0167	0.0270
		0.0276		1373		0.0324
		0.0284		1377		0.0318
	20	0.0220	0.0186	804	811	0.0059	0.0057
		0.0179		959		0.0051
		0.0160		671		0.0060
Type C	5	0.0327	0.0296	1602	806	0.0379	0.0309
		0.0282		305		0.0271
		0.028		512		0.0276
	10	0.0375	0.0342	532	583	0.0377	0.0295
		0.036		290		0.0260
		0.0291		928		0.0247
	20	0.0251	0.0216	1881	1667	0.0392	0.0368
		0.0143		1817		0.0336
		0.0253		1304		0.0377

, and Figure 7. Figure 6 shows the sample of testing (adhesion strength) for a specimen with a thickness of 2 mm.

Table 3 shows the measured values and average values of cohesive strength, elongation, and toughness under the temperature conditions of 5 °C, 10 °C, and 20 °C for each of the three SPRG viscosity types. The average value of toughness was analyzed by viscosity and temperature, as shown in Figure 7. As for the cohesive strength according to the viscosity condition of SPRG, in the order of Type C (10 °C, 0.0342 N/mm²) > Type B (10 °C, 0.0251 N/mm²) > Type A (10 °C, 0.0115 N/mm²), it was confirmed that the higher the viscosity, the greater the cohesive strength appeared. In addition, the toughness according to the viscosity conditions of SPRG increases as the viscosity increases in the order of Type C (20 °C, 0.0368 N/mm²) > Type B (5 °C, 0.0294 N/mm²) > Type A (20 °C, 0.0123 N/mm²). The trend was confirmed (refer to Figure 7a) as shown in Figure 7b, the cohesion and toughness of SPRG according to the temperature environment tended to appear higher in the low temperature region (5 °C, 10 °C) than in the high temperature region (20 °C). In addition, it was found that the deviation of cohesion and toughness was larger in the high temperature region (20 °C) than in the low temperature region (5 °C, 10 °C).

Through this experimental analysis, in the case of SPRG with a thickness of 2 mm, the cohesive strength and toughness tended to increase as the viscosity increased in the order of Type C > Type B > Type A. It was found that the cohesive strength and toughness according to the effect of temperature showed higher toughness and stability in the low temperature region (5 °C, 10 °C) than the relatively high temperature region (20 °C).

3.2. Cohesive Strength and Toughness of 10 mm Thickness

Figure 8,

Table 4. Measurement result based on specimen types (10 mm thickness).

Specimen Types	Temperature (°C)	Cohesive Strength [N/mm2]	Avg. Cohesive Strength [N/ mm2]	Elongation [%]	Average Elongation [%]	Toughness [N/ mm2]	Average Toughness [N/ mm2]
Type A	5	0.0051	0.0046	3009	3075	0.0243	0.0192
		0.0050		3348		0.0172
		0.0037		2870		0.0160
	10	0.0029	0.0030	3341	3076	0.0073	0.0071
		0.0029		3009		0.0066
		0.0033		2879		0.0074
	20	0.0033	0.0031	2844	2920	0.0063	0.0067
		0.0025		2931		0.0048
		0.0036		2986		0.0089
Type B	5	0.0102	0.0092	1648	2127	0.1422	0.1229
		0.0085		2276		0.1243
		0.0088		2456		0.1021
	10	0.0083	0.0080	2184	2412	0.0785	0.0747
		0.0071		2960		0.0794
		0.0087		2093		0.0661
	20	0.0063	0.0071	2093	2147	0.0374	0.0352
		0.0081		2316		0.0363
		0.0069		2032		0.0321
Type C	5	0.0286	0.0289	517	1465	0.2461	0.2062
		0.0417		476		0.2222
		0.0163		3402		0.1503
	10	0.0252	0.0286	4680	5254	0.3236	0.3220
		0.0191		6445		0.3204
		0.0415		4637		0.3218
	20	0.0177	0.0161	10443	9490	0.2570	0.2703
		0.0153		7828		0.2913
		0.0152		10200		0.2627

, and Figure 9 show the results of measuring cohesive strength and toughness under the temperature conditions of 5 °C, 10 °C, and 20 °C for 10 mm thick specimens for each SPRG viscosity type. Figure 8 shows the measurement of viscosity and cohesive strength (adhesion strength) of a 10 mm thick sample.

Table 4 shows the measured values of cohesive strength, elongation, and toughness under the temperature conditions of 5 °C, 10 °C, and 20 °C for each of the three SPRG viscosity types and their average values. The average value of was divided by viscosity and temperature and analyzed as shown in Figure 9. The cohesive strength according to the viscosity condition of SPRG increases as the viscosity increases in the order of Type C (5 °C, 0.0289 N/mm²) > Type B (5 °C, 0.092 N/mm²) > Type A (5 °C, 0.046 N/mm²). In addition, the toughness according to the viscosity conditions of SPRG increases as the viscosity increases in the order of Type C (5 °C, 0.2062 N/mm²) > Type B (5 °C, 0.1229 N/mm²) > Type A (5 °C, 0.0192 N/mm²). The trend was confirmed (refer to Figure 9a). As shown in Figure 9b, the cohesion and toughness of SPRG according to the temperature environment tended to be higher in the low temperature region (5 °C, 10 °C) than in the high temperature region (20 °C).

Through this experimental analysis, in the case of 10 mm thickness of SPRG, the cohesive strength and toughness tended to be greater as the viscosity increased in the order of Type C > Type B > Type A. It was found that the cohesive strength and toughness according to the influence of temperature showed relatively higher toughness in the low temperature region (5 °C, 10 °C) than in the high temperature region (20 °C).

3.3. Comparison of 2 mm and 10 mm Thickness

Table 5. Comprehensive measurement results for each sample.

Specimen Types	Thickness	Temperature (°C)	Avg. Cohesive Strength [N/ mm2]	Average Elongation [%]	Average Toughness [N/mm2]
Type A	2 mm	5 °C	0.0195	1141	0.0123
		10 °C	0.0115	1400	0.0117
		20 °C	0.0136	695	0.0033
	10 mm	5 °C	0.0046	3075	0.0192
		10 °C	0.003	3076	0.0071
		20 °C	0.0031	2920	0.0067
Type B	2 mm	5 °C	0.0213	1409	0.0294
		10 °C	0.0251	1369	0.027
		20 °C	0.0186	811	0.0057
	10 mm	5 °C	0.0092	2127	0.1229
		10 °C	0.008	2412	0.0747
		20 °C	0.0071	2147	0.0352
Type C	2 mm	5 °C	0.0296	806	0.0309
		10 °C	0.0342	583	0.0295
		20 °C	0.0216	1667	0.0368
	10 mm	5 °C	0.0289	1465	0.2062
		10 °C	0.0286	5254	0.322
		20 °C	0.0161	9490	0.2703

shows the average values of cohesive strength and elongation toughness for each type of SPRG viscosity and thickness of 2 mm and 10 mm specimens for each temperature condition.

(1)

Comparison of cohesive strength

Figure 10 shows the results of comparison of the cohesive strength of the 2 mm and 10 mm thick specimens. Comparison of cohesive strength according to the thickness of the SPRG sample shows that the cohesive strength of 2 mm thickness is greater than that of 10 mm thickness in types A, B, and C viscosities. In a comparison of the cohesive strength according to the viscosity, it was found that the cohesive strength deviation was large according to the thickness difference in the low viscosity (Type A) or the medium viscosity (Type B), but the deviation was not large in the high viscosity (Type C). In a comparison of cohesive strength according to temperature conditions, it was found that in the low viscosity (Type A) or medium viscosity (Type B), the cohesive strength deviation was large according to the thickness difference at all temperatures, but the deviation was not large in high viscosity (Type C).

(2)

Comparison of elongation rates

Figure 11 shows the comparison results of elongation rates of 2 mm and 10 mm thick specimens. Comparison of the elongation according to the thickness of the SPRG sample showed that the 10 mm thickness showed a greater elongation than the 2 mm thickness in types A, B, and C viscosities and temperature conditions. Comparing the elongation rate according to the difference in viscosity, it can be seen that the elongation rate is greater at high viscosity (Type C) than at low viscosity (Type A) or medium viscosity (Type B). Comparison of elongation rates according to temperature conditions shows that, at low viscosity (Type A) or medium viscosity (Type B), the elongation deviation is not large at all temperatures of 2 mm and 10 mm, but at high viscosity (Type C) there is a large deviation. In the case of elongation, as the thickness of the material increases, the amount of material increases accordingly, so the intermolecular elongation range is widened, so it is judged that the elongation is measured to be high. In addition, it is determined that when the temperature is high, the flexibility is increased, so that the elongation occurs better and the elongation rate is increased.

(3)

Comparison of toughness

Figure 12 shows the comparison result of the toughness of the 2 mm and 10 mm thick specimens. A comparison of the toughness according to the thickness of the SPRG sample shows that the 10 mm thickness is greater than the 2 mm thickness. Comparison of toughness in all viscosities and temperature condition of Type A, B, and C shows that toughness greatly increases according to the difference in thickness at high viscosity (Type C) than at low viscosity (Type A) or medium viscosity (Type B). Comparison of toughness according to temperature conditions showed that there was little difference in thickness at low viscosity (Type A), medium viscosity (Type B) at low temperature, and temperature at high viscosity was not significantly affected.

Similar to elongation, it is judged that as the amount of material increases as the thickness of the material increases, the potential energy of the material itself, that is, the energy to resist external force due to the high internal cohesive strength, was measured. However, at low temperature, the arrangement between molecules is condensed to maintain a close shape, but as the temperature increases, the arrangement is loosened and the toughness decreases.

3.4. Prediction Result of Hydraulic Response

By substituting the average toughness analyzed in Section 3.3 into the hydrostatic pressure equation (hydrostatic resistance) of Figure 3, the expected underground depth can be converted as shown in

Table 6. Comprehensive toughness of specimen types in accordance with thickness and temperature.

Specimen Type	Thickness (mm)	Temperature (°C)	Average Toughness [N/mm2]	Expected Resistance Capacity Relative to Underground Depth [m]
Type A	2	5	0.0123	1.2
		10	0.0117	1.2
		20	0.0033	0.3
	10	5	0.0192	1.9
		10	0.0071	0.1
		20	0.0067	0.1
Type B	2	5	0.0294	2.9
		10	0.0270	2.7
		20	0.0057	0.6
	10	5	0.1229	12.3
		10	0.0747	7.5
		20	0.0352	3.5
Type C	2	5	0.0309	3.1
		10	0.0295	3.0
		20	0.0368	3.7
	10	5	0.2062	20.6
		10	0.3220	32.2
		20	0.2703	27.0

below.

Based on the results shown in Table 6 above, it is judged that the low-viscosity Type A should be used only in the very shallow underground of 1 m or less under the assumption that the temperature at the depth of the underground is maintained at an average of 10 °C. It is judged that Type B of medium intensity can be used from 2 m to 7 m underground. It is judged that the high viscosity Type C can be used from 3 m to 32 m underground.

Based on the above results, trend lines and equations were obtained as shown in Figure 13 based on the average toughness value of 10 °C for each SPRG viscosity type, and then the toughness values according to thickness were checked. It was confirmed that the low-viscosity Type A, regardless of the increase in toughness, decreased as the thickness of the material increased, and converted to a negative region around 22 mm in thickness. It means that the viscosity is low in spite of applying a thickness greater than that, which means that it cannot resist water pressure and is lost. Since Type B of medium strength does not have a large increase in toughness with increasing thickness, it is predicted that a thickness of 30 mm or more should be secured to cope with water pressure of 20 m. If it is to be used at a depth of 100 m or more, it is predicted that the SPRG must be constructed with a thickness of about 165 mm or more to cope with water pressure of 100 m. It can be confirmed from Figure 13 that the increase in toughness of Type C with high viscosity is proportional to the increase in the thickness of the material, and the increase is confirmed to be very large.

Therefore, it is predicted that it is possible to respond when the thickness is about 28 mm or more at a depth of 100 m or more. Thus, it was found that it is possible to use SPRG having a quality and viscosity equal to or higher than that of Type C in order to block water leakage in an actual deep underground tunnel, etc.

4. Conclusions

In this study, correlations of environmental and material workability conditions including temperature, viscosity, cohesive force, adhesion strength, toughness, and water pressure resistance were analyzed to present quality standards for proper filling amount and thickness management for on-site quality control when using SPRG leak repair materials. Based on presented analysis, a theory was presented that can determine the water pressure resistance according to the change in the underground depth according to the viscosity and thickness, and the conclusion of this study is as follows:

(1)

In this study, an experimental method to reproduce the behavior of cracks injected with SPRG type repair materials was presented. The adhesion and elongation of the leak repair material obtained through this experiment were interpreted as ‘toughness’ and ‘water pressure resistance’, and a theory that can be viewed as an equivalent physical force was presented;

(2)

Based on this method, a correlation between viscosity, cohesive strength, toughness, and hydraulic resistance of SPRG used as a leak crack repair material for concrete structures was presented. Based on this analysis, study results suggested the appropriate thickness to resist the water pressure in the underground depth for SPRG of high viscosity, medium viscosity, and low viscosity. In this regard, it was found that a thickness of about 28 mm or more was required for high-viscosity SPRG at 100 m underground, and it was found that even with the same thickness, a high-viscosity material can resist higher water pressure. Limited within the scope of this testing and the SPRG types investigated, it was found that the SPRG types from the highest hydraulic resistance to lowest hydraulic resistance is Type C > Type B > and Type A;

(3)

This study demonstrates that an evaluation method (test method) can be made possible to evaluate leakage repair materials and their hydraulic resistance performance in various underground water pressure conditions. Therefore, in the future, the work to use the correlation of viscosity, toughness, and water pressure resistance of the repair materials presented in this study as a practical evaluation standard will be promoted.