J. Cent. South Univ. (2019) 26: 1863-1873

DOI: https://doi.org/10.1007/s11771-019-4140-5

A new clay-cement composite grouting material for tunnelling in underwater karst area

ZHANG Cong(张聪), YANG Jun-sheng(阳军生), FU Jin-yang(傅金阳),

OU Xue-feng(欧雪峰), XIE Yi-peng(谢亦朋), DAI Yong(戴勇), LEI Jin-shan(雷金山)

School of Civil Engineering, Central South University, Changsha 410075, China

Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract: A new clay-cement composite grouting material (CCGM) for tunnelling in underwater karst area was developed through the excellent synergistic interactions among cement, clay, meta-aluminate and lignin. The probable formation mechanism of the material was proposed based on a series of experimental tests. The results show that with an optimal mass ratio (2:1:1:0.024) for water, cement, clay and additives, the obtained CCGM displayed an excellent grouting performance for karst in an underwater condition. Compared with neat cement grouts and clay-cement grouts, CCGM has faster gel time, lower bleeding rate and bulk shrinkage rate, greater initial viscosity, and a strong resistance to water dispersion. A successful engineering application indicates that CCGM not only fulfils a better grouting performance for karst in underwater conditions but also reduces the engineering cost and environmental pollution.

Key words: tunnel; karst; underwater; new grouting material; clay-cement composite

Cite this article as: ZHANG Cong, YANG Jun-sheng, FU Jin-yang, OU Xue-feng, XIE Yi-peng, DAI Yong, LEI Jin-shan. A new clay-cement composite grouting material for tunnelling in underwater karst area [J]. Journal of Central South University, 2019, 26(7): 1863-1873. DOI: https://doi.org/10.1007/s11771-019-4140-5.

1 Introduction

The rapid development of transportation infrastructures in China requires more and more tunnels to be constructed in karst regions [1-6]. Research shows that 50% of domestic underground engineering and over 40% of long tunnels are constructed in karst regions [7]. Karst is recognized as a complex hydrology and geology system, and is often accompanied with caves, faults and fractures, which results in unpredictable adverse effects for tunnelling in this area, such as collapse, ground fissures, and water inrush [8, 9]. Over the past decade, many disastrous events associated with karsts in tunnels have been reported because of the geological complexity of karst [10-12]. Therefore, the crux of tunnel engineering construction in karst areas lies in how to avoid and address geological problems that may occur during the construction process. Grouting is one of the most effective and common ways to stabilize karst caves [13-15], in which grout is injected into cavities, voids and fractures to improve their mechanical and hydraulic properties, particularly in reducing permeability and deformability, and increasing strength and modulus of the karst ground formations [16-18].

Engineers have developed many grouting materials to deal with karst [19-21]. Among those materials for karst grouting, cement slurry is one of the most widely used materials because of its high intensity, inexpensiveness and availability of the raw material source. However, since cement slurry is a particulate material, there are still some difficult problems such as long setting time, poor stability and easy shrinkage of the concretion body. Later, cement grouts were replaced by clay-cement grouts. Clay-cement grouts are widely used in karst grouting because of their good performance. Compared with cement grouts, clay-cement grouts have advantages such as good stability, low permeability and low cost, but the materials are easily segregated by water in underwater karst. These problems make cement grouts and clay-cement grouts unreliable to fill karst in underwater conditions. Although some engineers have developed some chemical materials to attempt to solve this problem, the materials are extremely expensive and not environmentally friendly. Thus, it is necessary to search for a new grouting material with reliable performance to solve the karst problems in underwater conditions.

The paper presents a clay-cement composite grouting material (CCGM) for karst in underwater conditions. At first, the grouting performance and mechanical performance of CCGM for karst in underwater conditions are evaluated by a series of tests, and the formation mechanism of CCGM is proposed. A field grouting application is conducted to verify the superior performances of CCGM used for engineering grouting in karst area in an underwater condition.

2 Materials and methods

2.1 Raw materials

In this study, the cement was Nanfang 42.5 ordinary Portland cement with a specific density of 3.17 g/cm³ and a 28-d compressive strength of 45.5 MPa. The grain size distribution of the cement is listed in Table 1.

The clay was obtained from excavations at a depth of 2-8 m in the material yard of Hunan Province, China. The basics in situ characteristics were measured at Central South University and all tests were conducted according to the Chinese standard GB/T 50123-1999 [22]. The mineral components were measured using the SIMENS D500 X-ray diffractometer from Bruker, Switzerland. The particle size analysis was measured using OMEC LS-601 from Zhuhai, China. As results show that the clay is a kind of acidic clay of medium plasticity, and its properties make it suitable for grouting with cement. The grain size distribution is listed in Table 1 while the test results of its properties are listed in Table 2.

The modifier was made in-house and contained meta-aluminate and lignin. Meta- aluminate is a powder of alkaline white chemical substance which can significantly accelerate the hydration reaction of cement and shorten the setting time of the grout. Lignin is a phenolic polymer that can be used as a water-reducing agent to improve the mobility of grout.

2.2 Device of grouting experiment

The physical testing device was designed and fabricated as shown in Figure 1, which was composed of a pressure system and a karst system. The pressure system was composed of a gas cylinder, a constant-pressure valve, and a trachea. The gas cylinder was approximately 12 MPa; after depressurization through the constant-pressure valve and trachea, an experimental design pressure of 0-2 MPa was output to the grout storage system. The schematic layout of the karst cavity system is presented in Figure 1. It comprises a steel cylinder, which is 5 cm in diameter and 20 cm in height; the upper and lower sides are installed with a flange and fixed by bolts, which makes the installation and removal more convenient. A gas hole with a diameter of 1.5 cm was sited on the surface of upper flange, and a pressure gauge was fitted to the surface to record the pressure during grouting. Some drain holes with a diameter of 0.2 cm were drilled on the bottom surface of the lower flange, and a circular groove was set on the bottom surface to install a permeable stone and filter paper. This experimental setup enables one to inject grouts of different grouting parameters into a karst.

Table 1 Cement and clay grain size distribution

Table 2 In situ properties of silty clay

Figure 1 Schematic layout of model test

2.3 Testing program

To prepare CCGM, the clay (smaller than the size of 75 μm) was soaked in water for 12 h and stirred by a rotating mixer at 1000 r/min for 15 min, and the specific gravity of the slurry was adjusted. Afterwards, appropriate amounts of cement and clay slurry were thoroughly mixed by a rotating mixer at 1000 r/min for 5 min to form stable clay-cement grouts. Finally, the appropriate amounts of modifier was added to the clay-cement grouts and stirred for 5 min using a rotating mixer (1000 r/min) to form the CCGM. To study the properties of the CCGM for karst in an underwater condition, we placed the fresh CCGM into the karst cavity until saturation of the karst cavity. In addition, a constant-pressure injection to karst cavities was applied for 15 min. At the end, the fresh specimens were retrieved for the performance test. All the processes were performed under a standard temperature ((25±2) °C).

The purpose of the experiments was to verify the performance of the CCGM for karst in an underwater condition. For comparison, the cement grouts and clay-cement grouts were also analyzed. According to previous grouting engineering experience, a relatively small pressure and a low water-cement ratio are normally used to fill the karst cavity. Therefore, the grouting pressure of 1 MPa and water-cement ratio of 1:1 were used in this experiment. The clay content is commonly determined based on several factors. In this study, the clay content of 50% was selected considering the water cement ratio and grouting pressure. Detailed information of the grouting material and grouting parameters is provided in Table 3. The gel time, bleeding water, bulk shrinkage rate and retention rate were altered by changing the amount of modifier, and the testing scheme is shown in Table 4.

Table 3 Detailed ratio information of grouting material with grouting pressure of 1 MPa

Table 4 Test scheme for different modifiers with m(Water): m(Clay): m(Cement)=1:0.5:0.5

2.4 Testing methods

According to the testing program and mix proportion in Table 3, the fresh specimens were retrieved for the performance test. The gel time of the grouts was measured using the inverted-cup method. In this work, the ratio of the volume of bleeding water from the grouts in the grouting process (V₀) to the initial volume of grouts (V) is called the bleeding rate (V₀/V). The bulk shrinkage rate is defined as the final value of (V₁-V₂)/V₁, where V₂ is the volume of specimens after they have solidified in an underwater condition, and V₁ is the initial volume of the specimens. All the processes in this work were performed under a standard temperature ((25±2) °C, 95% humidity).

To verify the water-resistant dispersion of the material, experiments were conducted at a low flow velocity (0.2 m/s) in a transparent flume of 4 m length, 0.3 m width and 0.3 m height (Figure 2). When testing, the fresh specimens (mass, m) were removed to place in the transparent flume and the residual specimens (mass, m₀) were weighed after scouring for 5 min. The retention rate is defined as the final value of m₀/m [23].

Figure 2 Water-resistant dispersion test device

The rheological flow curves were obtained using the R/S Plus rheometer from Brookfield Ltd., USA. For the rheological model test, the shear rate was increased from 0 to 60 s^-1 over a period of 2 min, and the test result was analyzed using the software Rheo3000.

When we tested the mechanical properties of the grouts, the fresh specimens were kept in the karst cavity for 12 h until the grout developed a suitable strength. Then, the specimens were demolded, and a soil cutter was used to trim the specimens into 100-mm-high samples with 50 mm diameter (Figure 3(a)). The samples were stored underwater ((25±2) °C) until the testing ages (1, 3, 7 and 28 d). The unconfined compressive strength of the specimens was tested using the STYE-3000C universal testing machine, and the compression speed during the test was controlled at 5 mm/min (Figure 3(b)).

After 28 d of curing, a layer of polyurethane with a thickness of approximately 1-2 mm was uniformly coated on the surface of the cylindrical specimens, and the specimens were pressed into the karst cavity system. Then, we injected water into the karst cavity system with a constant pressure. We recorded the change in water level in the cylinder in a certain period, and the permeability coefficient was calculated using the method of constant head [24].

The microstructure of the grouting materials was examined using a HELIOS Nano Lab 600i field-emission scanning electron microscope (FEI Ltd, Hillsboro, USA) operating at 25 kV.

3 Results of CCGM performance

3.1 Gel time

The gel time is an important parameter to determine the pumping time and diffusion radius of grouting. In addition, a shorter gel time of grouts is beneficial for solidifying in underwater conditions. The gel time test results of the grouts are summarized in Table 5. Table 5 shows that the gel time of the CCGM can be controlled and it has a much shorter gel time than the cement grouts and clay-cement grouts, which implies that CCGM can stably fill the karst in underwater conditions. From A1 to A3, as the meta-aluminate content increases, the gel time of CCGM decreases almost linearly. From B1 to B3, as the lignin content increases, the gel time of CCGM increased slightly.

Figure 3 Photos of specimens stored (a), compression testing machine (b) and samples destruction (c)

Table 5 Gel time of grouts (min)

The above result shows that the gel time of CCGM is mainly affected by the meta-aluminate, which is an efficient accelerator that can significantly accelerate the hydration reaction of cement. It is worth noting that CCGM is no longer suitable for pumping when the meta-aluminate content is excessive.

3.2 Bleeding rate and bulk shrinkage rate

The stability of grouts can assess by the bleeding rate. A lower bleeding rate means the grouts is more stable. Table 6 shows the bleeding rate of grouts in the tests, where the addition of clay and modifier substantially decreased the bleeding rate. For example, CCGM and clay-cement grouts had 82.1% and 37.5% reduction in bleeding rate, respectively, compared with the cement grouts. From A1 to A3, as the meta-aluminate content increases, the bleeding rate of CCGM tends to decrease. From B1 to B3, as the lignin content increases, the bleeding rate of CCGM increases by 28.6%. The bleeding rate of CCGM is significantly raised by increasing the lignin content. Thus, clay can improve the stability of clay-cement grouts, and the stability can be further improved by adding meta-aluminate.

Table 6 also shows the bulk shrinkage rate of grouts in the tests. The bleeding rate is consistent with the law of the bulk shrinkage rate. It was remarkable that the bulk shrinkage rate of CCGM was 0, which is significantly less than that of other grouts. The bleeding rate and bulk shrinkage rate are important in grouting engineering. Lower bleeding rate and bulk shrinkage rate indicate better grouting effectiveness. In other words, CCGM is better than cement grouts and clay-cement grouts for grouting karst in underwater conditions.

Table 6 Bleeding rate and bulk shrinkage rate of grouts

3.3 Rheological properties

The rheological model of grouts can be discussed based on the flow curves drawn by different shear rate versus shear stress. The graph of shear stress versus shear strain rate for cement grouts, clay-cement grouts and CCGM is shown in Figure 4.

Figure 4 Flow curves of grouts

The relationship between the shear stress and the shear strain rate was examined using Bingham model for all grouts. However, CCGM had a higher initial shear yield stress than cement grouts and clay-cement grouts. Therefore, CCGM can hardly be separated by water when grouting in karst under groundwater, and the diffusion range of CCGM can be controlled.

3.4 Retention rates

The water-resistant dispersion of the grouts significantly affects the grouting effect in karst under groundwater. The retention rate is an important index to assess the ability of the water-resistant dispersion of the grouts: a higher retention rate implies that the grout is more conducive to grouting in karst under groundwater. The results of the water-resistant dispersion experiments are shown in Table 7. The retention rates of cement grouts, clay-cement grouts and CCGM were 21.3%, 62.4% and 88.7%, respectively. Thus, CCGM has excellent properties to resist water dispersion, and it is suitable for grouting in karst in underwater conditions. From A1 to A3, when the meta-aluminate content (in proportion) increased from 0.005 to 0.015, the retention rate increases by 22.1%. From B1 to B3, as the lignin content increased, the retention rate of CCGM reduced slightly. The results show that the meta- aluminate content have the greatest impact on the retention rate, and the lignin content has the least influence on the retention rate. We must mention that the total grouting volume should consider the dispersed grout volume by water.

Table 7 Retention rates of grouts (%)

3.5 Mechanical characteristics

The obtained CCGM exhibited intriguing mechanical characteristics as shown in Table 8. The early compressive strength (1 and 3 d) almost matched that of cement grouts, although a lot of clay was added. The 28-d compressive strength of CCGM was approximately 5.8 MPa, and the permeability coefficient was less than 10^-6 cm/s. Significantly, even with the curing in an underwater condition, its compressive strength and impermeability reached the requirements of karst grouting engineering.

Table 8 Scouring rate and mechanical characteristics of grouts

3.6 Microscopic structure

The superior performance of CCGM can be closely related to its microscopic structure. The microscopic structure of CCGM was identified via SEM images, and for comparison, the SEM images of cement and clay-cement were also analyzed.Figure 5 shows the SEM images of samples.Figures 5(a)-(c) show the cross-sectional SEM images of cement grouts, clay-cement grouts and CCGM, respectively. As shown in Figure 5, the fracture surface of CCGM was more compact than cement grouts and clay-cement grouts. We find that the cement and clay particles in CCGM were interconnected with each other to form a stable pellet network structure, and some hydration products were distributed between networks to form an integrated whole. The above SEM observation shows that the structure of CCGM is favorable because of its mechanical performance and stability of grouts.

Figure 5 SEM images:

4 Discussion

4.1 Formation mechanism of CCGM

The basic components of CCGM are clay, cement, meta-aluminate and lignin, each of which plays its own role. The formation mechanism of the CCGM can be described as follows. When cement is uniformly dispersed in the clay slurry, there is a strong interaction between clay particles and cement particles to form cement-clay balls [25, 26]. Therefore, the cement hydration is carried out around cement-clay balls, and hydration products continue to fill the pore-forming strength among the cement-clay balls. However, clay particles can easily be attracted by calcium ions from the hydration products of cement, which creates a stable pellet structure. More importantly, the cementitious particles formed by the hydration of cement combining with the pellet structure to thicken the clay-cement grouts. As a result, the stability of the clay-cement grouts is improved, and the bleeding rate decreases.

A series of complicated physical and chemical hydration reactions quickly occurs after we add admixtures (meta-aluminate and lignin) to the clay-cement grouts. After meta-aluminate is added to the clay-cement grouts, many NaOH and Al(OH)₃ molecules are produced; then, Al(OH)₃ can react with calcium hydroxide and gypsum (an ingredient of cement) [27,28]. The dissolving rate of the calcium aluminate phase and calcium silicate phase in the cement system is accelerated. Meanwhile, during the hydration process, meta-aluminate generates more heat and increases the temperature of the grouts, which further promotes the cement hydration. In addition, the combination of many Ca(OH)₂, SO₄^2-, AlO₂^-, etc. ions generates ettringite and the Ca(OH)₂ concentration decreases, which further promotes cement hydration. As a result, the gel time of CCGM is reduced, and the initial yield shear stress and early-age strength of CCGM are enhanced. Previous studies have shown that lignin is used as a dispersing agent or superplasticizer for cement grouts [29, 30]. On the one hand, lignin is a surfactant that can decrease the surface tension of water. When lignin is added to clay-cement grouts, the degree of dispersion of the cement particles and clay particles in the water will increase. Therefore, it reduces the cement hydration and the production of granular spheres between cement and clay. On the other hand, many hydrophilic groups will be generated when lignin is added to clay-cement grouts, and the hydrophilic groups will adsorb on the surface of cement particles to form a water film, which decreases the friction among the cement particles. Meanwhile, lignin can generate small bubbles during the mixing process of lignin and water, which also reduce the friction among the cement particles. As a result, the fluidity of CCGM increases.

Based on the excellent synergistic interactions among cement, clay, meta-aluminate and lignin, a new grouting material (CCGM) was developed with high stability, good pumpability, large initial viscosity, adjustable setting time, strong water- resistant dispersion, satisfactory compressive strength and permeability performance.

4.2 Properties of CCGM for tunnelling in underwater karst area

Generally, grouting material for karst tunnel in underwater conditions needs fast solidifying，a high stability and initial viscosity, a low bleeding rate and bulk shrinkage rate, sufficient early compressive strength as well as lower permeability and scour resistance. In this paper, based on the research institution, design and construction unit involved, the recommended parameters for the grouting material include a gel time between 30 to 45 min, a bleeding rate of less than 15%, and a retention rate of more than 80% with a flow velocity of approximately 0.2 m/s. The early compressive strength should be more than 1 MPa and 28-d compressive strength should be more than 5 MPa, and the permeability coefficient should be less than 10^-5 cm/s. Laboratory experiments and engineering applications reveal that the developed new clay-cement composite grouting material (CCGM) for tunnelling in underwater karst area is a Bingham fluid with a higher initial shear yield stress. The gel time of CCGM can be controlled in the range of 5 to 50 min by varying the amount of meta-aluminate and lignin. The clay significantly reduces the permeability and the bleeding rate, but it has a negative effect on the compressive strength. Furthermore, CCGM is subject to dynamic water scouring, and the retention rate firstly increases with meta-aluminate content and then it maintains at a relatively stable level. In a word, CCGM performs excellently for karst area grouting in an underwater condition with the recommended optimal mass ratio (2:1:1:0.024 for water, cement, clay, and additives, respectively).

It is worth noting that the engineers are very concerned about project cost and environment in underwater karst grouting engineering, because the grouting volume in underwater karst is very large. The field grouting test found that the depth of the test hole was 30 m and the grouting pressure was raised from 0 to 0.8 MPa. The grouting volume of cement grouts, clay-cement grouts and CCGM were 532.6 m³, 317.6 m³ and 154.5 m³, respectively. The cost of CCGM was only one-third as much as the cement grouts and no adverse effect was monitored to the water quality.

5 Field application

The subway traffic tunnel was planned to be built underwater in Xiangjiang River in Changsha City, Hunan Province, China. By exploring around the axis of the tunnel, we have discovered complex geology conditions including soft soil, sand gravel and a large amount of limestone. The karst proportion in the area is above 35%, most of which is under the water level of Xiangjiang River. There are many karst caverns detected by the bore hole investigation, and these caverns are presented with the vertical diameter (D) distribution of 26.5% for D<1 m, 38.8% for 1 m6 m. The minimum vertical diameter is 0.2 m and the largest vertical diameter is 22.46 m. The karst caverns are mainly filled with fine sand and silt. Additionally, the karst caverns was found in random distribution, and the distances from the karst caverns to the tunnel alignment are no more than 20 m and their depths to the river bed are from 10 up to 50 m. The water in the karst, which is interlinked with the river, increases the possibility of water inrush during the tunnel excavation. The permeability of the karst regions is approximately 5×10^-5 cm/s (Figure 6).

To facilitate the construction, a steel platform with an area of approximately 4000 m² was set up on the river (Figure 7). Around the axis of the tunnel, four rows of grouting holes were arranged according to the plum blossom type, and the distance between any two grouting holes was 1.5 m. The CCGM had the recommended water/cement ratio of 2, a clay content of 50%, a meta-aluminate content of 2%, and a lignin content of 0.4%. The parameters of the grouting were strictly controlled. when the grouting pressure reached 1 MPa, we continued grouting for 30 min.

To test the effect of the grouting, in-situ water- pumping experimental tests were carried out at typical sampling holes after 28 d of grouting [31, 32]. Figure 8(a) shows the in-situ water- pumping experimental tests. The results indicate that the permeability coefficient was decreased to 10^-5 cm/s which is below the required value by the design institute. To check the quality of the grouted karst ground, samples were taken from the typical drilling holes, as shown in Figure 8(b). Their compressive strengths were tested by indoor experiments. It was found that the compressing strength of the grouted body after 28 d increased to 2 MPa which is sufficient enough for tunnel excavation according to the requirement of design institute. Moreover, the total grouting volume of CCGM was 651 m³. The average value of grouting volume of CCGM was 0.38 m³ per meter of each grouting hole which is far lower than the grouting volume of using cement grouts or clay-cement grouts per meter of each grouting hole. The cost of CCGM is about 438 RMB per cubic meter while the cost of cement grouts or clay-cement grouts is almost the same. However, The amount of grouting material consumption using CCGM is much smaller than using cement grouts or clay- cement grouts, and the CCGM has a superior performance in engineering practice. There are no monitored adverse effects to the water quality of the Xiangjiang River during the construction according to result of the environmental protection department.

Figure 6 Engineering geology

Figure 7 Steel platform and site layout

Figure 8 Photos of in-situ water-pummping experimental tests (a) and samples (b)

6 Conclusions

In this paper, a cheap and environmentally friendly grouting material was developed to overcome the shortcomings of traditional grouting materials for tunnelling in underwater karst area. A series of experiments and a field case study were conducted to check the properties of the material and to verify the field performance of the material. The major conclusions are as follows.

1) The excellent synergistic interactions among cement, clay, meta-aluminate and lignin can lead to a grouting material of CCGM with a superior performance. The results of experimental test show that CCGM provides a faster gel time, a higher initial yield stress and a greater early strength than the cement grouts and clay-cement grouts. Moreover, the CCGM has a superior water-resistant dispersion performance to form a cohesive integration to fill the karst caves under water, thereby providing a solid surrounding rock for tunnelling under water.

2) The properties of CCGM can be adjusted by controlling the amount of meta- aluminate, lignin and clay, which in turn influences the quality of grouting. The gel time and retention rates of CCGM can be controlled by varying the amount of meta-aluminate and lignin. The clay can significantly reduce the permeability and the bleeding rate, but it has a negative effect on the compressive strength. The results of experimental test show that with an optimal mass ratio (2:1:1:0.024) for water, cement, clay, and additive, the obtained CCGM displayed an excellent grouting performance for karst in an underwater condition.

3) Due to the addition of a large amount of clay, the compressive strength of CCGM is moderate and its permeability is lower than that of the cement material. CCGM will greatly reduce the project cost and minimize the environmental pollution as a low-cost and environmentally friendly raw material, and the amount of cement is significantly reduced.

References

[1] GUO Fang, JIANG Guang-hui, YUAN Dao-xian, POLK J S. Evolution of major environmental geological problems in karst areas of Southwestern China [J]. Environmental Earth Sciences, 2013, 69(7): 2427-2435.

[2] CUI Qing-long, WU Hui-na, SHEN Shui-long, XU Ye-shuang, YE Guan-lin. Chinese karst geology and measures to prevent geohazards during shield tunnelling in karst region with caves [J]. Natural Hazards, 2015, 77(1): 129-152.

[3] YANG Zi-han, ZHANG Jia-hua. Minimum safe thickness of rock plug in karst tunnel according to upper bound theorem [J]. Journal of Central South University, 2016, 23(9): 2346-2353.

[4] SHI Shao-shuai, XIE Xiao-kun, BU Lin, LI Li-ping, ZHOU Zong-qing. Hazard-based evaluation model of water inrush disaster sources in karst tunnels and its engineering application [J]. Environmental Earth Sciences, 2018, 77(4): 141.

[5] CUI Qing-long, SHEN Shui-long, XU Ye-shuang, WU Huai-na, YIN Zhen-yu. Mitigation of geohazards during deep excavations in karst regions with caverns: A case study [J]. Engineering Geology, 2015, 195: 16-27.

[6] CHENG W C, CUI Qing-long, SHEN Shui-long, ARULRAJAH A, YUAN Da-jun. Fractal prediction of grouting volume for treating karst caverns along a shield tunneling alignment [J]. Applied Sciences, 2017, 7(7): 652.

[7] LI Shu-cai, LIU Ren-tai, ZHANG Qing-song, ZHANG Xiao. Protection against water or mud inrush in tunnels by grouting: A review [J]. Journal of Rock Mechanics and Geotechnical Engineering, 2016, 8(5): 753-766.

[8] ALIJA S, TORRIJO F J, QUINTA-FERREIRA M. Geological engineering problems associated with tunnel construction in karst rock masses: The case of Gavarres tunnel (Spain) [J]. Engineering Geology, 2013, 157(4): 103-111.

[9] LI Li-ping, TU Wen-feng, SHI Shao-shuai, CHEN Jian-xun, ZHANG Yan-huan. Mechanism of water inrush in tunnel construction in karst area [J]. Geomatics Natural Hazards and Risk, 2016, 7(sup1): 35-46.

[10] KNEZ M, SLABE T, EBELA S, GABROVEK F. The largest karst cave discovered in a tunnel during motorway construction in Slovenia’s Classical Karst (Kras) [J]. Environmental Geology, 2008, 54(4): 711-718.

[11] SONG K I, CHO G C, CHANG S B. Identification, remediation, and analysis of karst sinkholes in the longest railroad tunnel in South Korea [J]. Engineering Geology, 2012, 135-136: 92-105.

[12] CHENG Wen-chieh, SONG Zhan-ping, TIAN Wei, WANG Zhi-feng. Shield tunnel uplift and deformation characterisation: A case study from Zhangzhou Metro [J]. Tunnelling and Underground Space Technology, 2018, 79: 83-95.

[13] XIE Zhong-qiu, ZHANG Yu-chi, XIAO Hong-bin, FAN Jin-zhao. Acoustic full wave logging of karst foundation grouting effect evaluation [J]. Journal of Central South University (Science and Technology), 2012, 43(7): 2757-2761. (in Chinese)

[14] ZHANG Qing-song, LI Peng, WANG Gang, LI Shu-cai, ZHANG Xiao, ZHANG Qian-qing. Parameters optimization of curtain grouting reinforcement cycle in yonglian tunnel and its application [J]. Mathematical Problems in Engineering, 2015: 615736.

[15] SHI Hai, BAI Ming-zhou, XING Shao-chuan. Mechanics parameter optimization and evaluation of curtain grouting material in deep, water-rich karst tunnels [J]. Advances in Materials Science and Engineering, 2017: 1853951.

[16] NICHOLS S C, GOODINGS D J. Physical model testing of compaction grouting in cohesionless soil [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2000, 126(9): 848-852.

[17] SHIN J H, ADDENBROOKE T I, POTTS D M. A numerical study of the effect of groundwater movement on long-term tunnel behaviour [J]. Géotechnique, 2002, 52(6): 391-403.

[18] WANG Z F, SHEN J S, CHENG W C. Simple method to predict ground displacements caused by installing horizontal jet-grouting columns [J]. Mathematical Problems in Engineering, 2018: 1897394.

[19] LI Zhi-lin, WANG Xin-hua, XIE Li-zhao. Testing and applied research on grouting materials on karst tunnel water inrush [J]. Electronic Journal of Geotechnical Engineering, 2012, 17: 2933-2942.

[20] WEI Tao, ZHANG Da, CHEN Liang. The kinetics study and reaction mechanism of acrylate grouting materials [J]. Construction and Building Materials, 2015, 47: 89-92.

[21] CUI Wei, HUANG Jun-yan, SONG Hui-fang, XIAO Ming. Development of two new anti-washout grouting materials using multi-way ANOVA in conjunction with grey relational analysis [J]. Construction and Building Materials, 2017, 156: 184-198.

[22] GB/T 50123-1999. Standard for soil test method [S]. (in Chinese)

[23] ZHANG Cong, YANG Jun-sheng, ZHANG Gui-jin, YE Xin-tian, ZHANG Zhi-bo, LEI Jin-shan. Experimental study and engineering application of anti-washout properties of underwater karst grout [J]. Chinese Journal of Geotechnical Engineering, 2017, 39(10): 1859-1866. (in Chinese)

[24] ZHANG Cong, YANG Jun-sheng, ZHANG Gui-jin, ZHANG Jian. Experimental study on the anti-permeability of clay hardening grouts filling in water-rich karst [J]. Journal of Huazhong University of Science and Technology (Natural Science Edition), 2017, 45(2): 117-122. (in Chinese)

[25] WANG Xing-hua, ZHOU Hai-lin. An improved hyperbola rheological model for fresh cement-clay grouts [J]. Tunnelling and Underground Space Technology, 2001, 16(4): 353-357.

[26] SAVAGE D. Constraints on cement-clay interaction [J]. Procedia Earth and Planetary Science, 2013, 7: 770-773.

[27] PASTOR C, FERNNDEZ JIMNEZ A, VZQUEZ T, PALOMO . Calcium aluminate cement hydration in a high alkalinity environment [J]. Materiales De Construccion, 2009, 59(293): 21-34.

[28] FERNNDEZ-JIMNEZ A, VZQUEZ T, PALOMO A. Effect of sodium silicate on calcium aluminate cement hydration in highly alkaline media: A microstructural characterization [J]. Journal of the American Ceramic Society, 2011, 94(4): 1297-1303.

[29] KAMOUN A, JELIDI A, CHAABOUNI M. Evaluation of the performance of sulfonated esparto grass lignin as a plasticizer–water reducer for cement [J]. Cement and Concrete Research, 2003, 33(7): 995-1003.

[30] OUYANG Xin-ping, KE Li-xuan, QIU Xue-qing, GUO Yong-xia, PANG Yu-xia. Sulfonation of alkali lignin and its potential use in dispersant for cement [J]. Journal of Dispersion Science and Technology, 2009, 30(1): 1-6.

[31] SHEN Shui-long, CUI Qing-long, HO C E, XU Ye-shuang. Ground response to multiple parallel microtunneling operations in cemented silty clay and sand [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2016, 142(5): 04016001.

[32] CHENG W C, NI J C, ARULRAJAH A, HUANG Hui-wen. A simple approach for characterising tunnel bore conditions based upon pipe-jacking data [J]. Tunnelling and Underground Space Technology, 2018, 71: 494-504.

(Edited by ZHENG Yu-tong)

中文导读

新型的水下岩溶注浆黏土水泥复合材料

摘要：本研究利用水泥、黏土、偏铝酸盐及木质素之间良好的协同作用，研制了一种新型水泥复合灌浆材料(CCGM)用于富水岩溶盾构隧道注浆工程，并通过系列室内实验提出了新型水泥复合灌浆材料的形成机理。研究结果表明，在水、水泥、黏土和添加剂的最佳配比(2：1：1：0.024)下，所制得的CCGM注浆性能最优；与纯水泥浆和黏土水泥浆相比，CCGM具有较短的凝胶时间、较小的流动度和体积收缩率、较大的初始黏度以及较强的抗水分散性。工程应用表明，该注浆材料在富水岩溶环境下注浆性能优越，并且可以降低工程造价和减小环境污染。

关键词：隧道；岩溶；水下；新型灌浆材料；黏土水泥复合材料

Foundation item: Project(51608539) supported by the National Natural Science Foundation of China; Projects(2016M592451, 2017T100610) supported by the China Postdoctoral Science Foundation

Received date: 2018-05-16; Accepted date: 2018-11-07

Corresponding author: FU Jin-yang, PhD, Associate Professor; Tel: +86-18874758036; E-mail: jyfu2010@163.com; ORCID: 0000- 0002-0632-1222