**Abstract**

With the rapid development of high-speed railway, high-speed railways pose new requirements on subgrade frost heave deformation control. Microheave in conventional non-frost-heave filler cannot meet the requirements of high-speed railways for high levels of smoothness and stability and threaten high-speed train operation safety. To solve problems of seasonal permafrost region subgrade filler microheave in China, combined laboratory test and theoretical analysis, this research analyzed the physical properties of frost heave influencing factors for microheave filler. The influence of skeleton grain during frost heave formation is revealed. The microheave filler frost heave development mechanism is investigated. On this basis, based on the principle of minimum energy, a frost heave calculation formula for microheave filler is deduced, and a frost heave deformation analysis model for microheave filler is created. In addition, the effectiveness of the model is demonstrated in an indoor test. This study provides a theoretical reference for controlling the frost heaving deformation of railway subgrade.

**Keywords:** high-speed railway subgrade, microheave filler, frost heave influencing factor, frost heave development mechanism, frost heave analysis model

#### **1. Introduction**

China now has the world's longest high-speed railway operation mileage, fastest operational speed and largest scale of projects under construction. By the end of 2016, the high-speed railway operational mileage had reached 2.2 <sup>10</sup><sup>4</sup> km, which was the largest in the world. Compared with normal speed railways, the major features of high-speed railways are that they are fast, comfortable and safe. For ballasted track, high-speed railway subgrade settlement should not exceed 5 or 3 cm in transition segments. For ballastless track high-speed railway subgrades, the ideal goal in actual projects is zero settlement, in particular for deformation-sensitive sections such as transit segments, for which settlement is controlled to be under 5 mm and to not exceed 1/1000 at corners. To achieve the above goal, track structure smoothness and stability should be guaranteed, which is reliant on providing track structures with subgrade structures of high strength, high rigidity, uniform longitudinal variation, high stability and durability. Currently, in northeast China, the Harbin-Dalian, Panjin-Yingkou, Harbin-Qiqihar, Shenyang-Dandong and Jilin-Hunchun high-speed railways span seasonal permafrost regions. Compared with high-speed railways in non-frost regions, for high-speed railways in permafrost regions, subgrade filler frost heave induces uneven settlement, which

has become a critical issue [1]. In northern China, all railway subgrades have developed various levels of frost heave, which directly threatens travelling safety [2].

frost heave forecast to a freeze-thaw cycle simulation [12]. Zhang and Michalowski introduced a THM (thermal-hydro-mechanical) model for frost heave sensitive soils such as viscous soils to describe temperature, hydraulic pressure and force field changes induced by freeze-thaw cycling and subsequent physical phenomena such as expansion and settlement; they also provided a numerical simulation for the onedimensional problem [13]. Bronfenbrener described heat and matter transfer in a fine grain porous medium with frost heave during a phase transition and provided a model for the problem with a movement boundary condition. Comparison with test data proved that within a certain level of precision, the model was viable for frost heave estimation [14]. Yin created a seasonal permafrost region, subgrade soil, multi-factor, frost heave rate forecast model via field measurements and theoretical

In this paper, based on a field survey in a permafrost region and high-speed railway subgrade filler and frost heave characteristics, the concept of subgrade microheave filler is proposed. A frost heave calculation formula for a microheave filler in closed systems is deduced via an indoor test and theoretical analysis. A frost heave deformation analysis model for microheave filler is created, and its effective-

**2. Experimental study on microheave filler frost heave influencing**

Upon conducting an experimental study, Wang et al. suggested that there were three categories of railway subgrade filler: over coarse grained soils, coarse grained soils and fine grain soils [16]. In this paper, the large amounts of coarse grained soil filler in high-speed railway subgrades in the seasonal permafrost region of China are

The bed filler used in high-speed railway subgrades in the permafrost regions of China is arranged as follows. A normal embankment bed surface is filled with a layer of 55-cm grading gravel, below which are 5 cm of thick coarse sand and 2.1 m of thick soil in two groups, A and B. In the frozen depth range, the embankment bed is filled with non-frost-heave soil in groups A and B, and soils in groups A, B and C exist below the beds. The top 1.0 m of the embankment bed floor is filled with nonfrost-heave filler in groups A and B. Based on the distribution of filler along the line, the lower sections have filler in groups A and B. Low embankment bed surfaces are filled with grading gravel. Non-frost-heave filler in groups A and B is used in the range of the upper meter of bed floors. The lower sections are filled with filler in groups A and B. In the bed floor lower sections, the grading gravel layer water content is 3.2–5.9%, and the fine grain content is 3.2–10.7%. In lower sections, the non-frost-heave soil filler water content generally is 3.7–9.2%, and the fine grain content is 0.4–9.3%. In seasonal permafrost regions, the entire beds are excavated and replaced. The bed surfaces are filled with grading gravel, the upper 1 m of the bed floors are filled with non-frost-heave filler in groups A and B, and the lower sections are filled with filler in groups A and B. The grading gravel layer water contents are 2.2–3.2%, the fine grain contents are 8.0–15.1%, the water contents in the lower section non-frost-heave soil filler are generally 3.7–9.2%, and the fine

Coarse grained soil frost heave tests and analysis proved that the factors that influence major coarse grained soil frost heave include the soil property, water content, temperature and load [17]. To investigate the characteristics of high-speed railway subgrade filler frost heave in permafrost regions, in this chapter, typical permafrost region subgrade soil samples were selected to perform soil property tests

analysis and applied it to a project [15].

*Frost Heave Deformation Analysis Model for Microheave Filler*

*DOI: http://dx.doi.org/10.5772/intechopen.82575*

ness is proven.

**factors**

called microheave filler.

grain contents are 10.9–16.9%.

**95**

In China, both existing high-speed trains and those under construction follow the guidelines in the *Code for Design of Special Subgrade of Railway* (TB10035-2006) regarding filler selection and the design of scattered row impermeable and antifrost-heave structures. That is, the standard for filler frost heave control is 1%. However, on high-speed railway subgrades in Northeast China, the maximum depth of frost reaches 3 m. According to this standard, subgrade frost heave deformation cannot meet the requirement for ballastless track deformation control. In addition, in the *Code for Design of Special Railway Subgrades*, the seasonal frozen soil frost heave grading object is natural frozen soil, not manually compacted subgrade filler. Therefore, the microheave deformation mechanism for subgrade filler should be investigated, and a microheave deformation analysis model should be created to provide a theoretical basis for specification development and engineering design.

Currently, subgrade seasonal frost heave problems worldwide are investigated via experiments and theoretical models. In an experimentally based investigation, Askar and Zhanbolat investigated the effects of freeze-thaw cycles on a high-speed highway subgrade; a frost heave test was performed using field soil samples to identify frost heave and frost heave pressure in regional soil samples and frost heave depth under different conditions. They suggested that frost heave could be effectively reduced by replacing frost heave sensitive soil with coarse grained soil and deploying a drainage system [3].

Konrad suggested that it was inadequate to determine if subgrade filler had an anti-frost property by grain grading alone; the frost heave properties of fine grains should also be considered [4]. In addition, the frost heave sensitivities of subgrade fillers with superior grading increase linearly with fine grain content and active mineral content [5]. Bilodeau et al. investigated the effects of grain grading and fine grain properties on frost heave sensitivity and found that when fine grain content was low, fine grain mineral composition and grading had greater impacts on frost heave sensitivity. In addition, fine grains with different uniformity coefficients resulted in different frost heave levels [6]. Uthus et al. suggested that the main factors that influenced frost heave were water and fine grains (active minerals). Among these factors, water had greater impacts on frost heave than the material elastic modulus [7].

Wang et al. suggested that frost heave sensitivity and strength of coarse grained soil were affected by fine grain content. Frost heave tests and triaxial tests showed that when the fine grain soil content was 5%, coarse grained soil had weak frost heave property but high shear strength [8]. Bilodeau et al. investigated the relation between freeze-thaw cycle and long-term compression-induced permanent displacement in subgrade coarse grained materials. The results showed that pressure had a greater influence in a saturated soil sample that had not undergone freezethaw cycling. In addition, freeze-thaw cycles had a significant influence [9]. Guo et al. performed a frost heave test in a closed system with various levels of water content and compactness as well as in an open system, investigated the Lanzhou-Xinjiang railway subgrade soil frost heave characteristics and reached a conclusion that due to water content replenishment, the frost heave rate in the open system significantly exceeded that in the closed system [10].

In a model-based investigation, Sheng et al. undertook a model test and discovered that train cycle load increased subgrade soil pore hydro-pressure; under the pump suction effect, water level was observed to rise to the frost heave layer, which resulted in continuous frost heave in a high-speed railway subgrade [11]. Abdalla et al. making reasonable assumptions, extended a porosity function model from a

*Frost Heave Deformation Analysis Model for Microheave Filler DOI: http://dx.doi.org/10.5772/intechopen.82575*

has become a critical issue [1]. In northern China, all railway subgrades have developed various levels of frost heave, which directly threatens travelling

*Geotechnical Engineering - Advances in Soil Mechanics and Foundation Engineering*

In China, both existing high-speed trains and those under construction follow the guidelines in the *Code for Design of Special Subgrade of Railway* (TB10035-2006) regarding filler selection and the design of scattered row impermeable and antifrost-heave structures. That is, the standard for filler frost heave control is 1%. However, on high-speed railway subgrades in Northeast China, the maximum depth of frost reaches 3 m. According to this standard, subgrade frost heave deformation cannot meet the requirement for ballastless track deformation control. In addition, in the *Code for Design of Special Railway Subgrades*, the seasonal frozen soil frost heave grading object is natural frozen soil, not manually compacted subgrade filler. Therefore, the microheave deformation mechanism for subgrade filler should be investigated, and a microheave deformation analysis model should be created to provide a theoretical basis for specification development and engineering design. Currently, subgrade seasonal frost heave problems worldwide are investigated via experiments and theoretical models. In an experimentally based investigation, Askar and Zhanbolat investigated the effects of freeze-thaw cycles on a high-speed highway subgrade; a frost heave test was performed using field soil samples to identify frost heave and frost heave pressure in regional soil samples and frost heave depth under different conditions. They suggested that frost heave could be effectively reduced by replacing frost heave sensitive soil with coarse grained soil and

Konrad suggested that it was inadequate to determine if subgrade filler had an anti-frost property by grain grading alone; the frost heave properties of fine grains should also be considered [4]. In addition, the frost heave sensitivities of subgrade fillers with superior grading increase linearly with fine grain content and active mineral content [5]. Bilodeau et al. investigated the effects of grain grading and fine grain properties on frost heave sensitivity and found that when fine grain content was low, fine grain mineral composition and grading had greater impacts on frost heave sensitivity. In addition, fine grains with different uniformity coefficients resulted in different frost heave levels [6]. Uthus et al. suggested that the main factors that influenced frost heave were water and fine grains (active minerals). Among these factors, water had greater impacts on frost heave than the material

Wang et al. suggested that frost heave sensitivity and strength of coarse grained soil were affected by fine grain content. Frost heave tests and triaxial tests showed that when the fine grain soil content was 5%, coarse grained soil had weak frost heave property but high shear strength [8]. Bilodeau et al. investigated the relation between freeze-thaw cycle and long-term compression-induced permanent displacement in subgrade coarse grained materials. The results showed that pressure had a greater influence in a saturated soil sample that had not undergone freezethaw cycling. In addition, freeze-thaw cycles had a significant influence [9]. Guo et al. performed a frost heave test in a closed system with various levels of water content and compactness as well as in an open system, investigated the Lanzhou-Xinjiang railway subgrade soil frost heave characteristics and reached a conclusion that due to water content replenishment, the frost heave rate in the open system

In a model-based investigation, Sheng et al. undertook a model test and discovered that train cycle load increased subgrade soil pore hydro-pressure; under the pump suction effect, water level was observed to rise to the frost heave layer, which resulted in continuous frost heave in a high-speed railway subgrade [11]. Abdalla et al. making reasonable assumptions, extended a porosity function model from a

significantly exceeded that in the closed system [10].

safety [2].

deploying a drainage system [3].

elastic modulus [7].

**94**

frost heave forecast to a freeze-thaw cycle simulation [12]. Zhang and Michalowski introduced a THM (thermal-hydro-mechanical) model for frost heave sensitive soils such as viscous soils to describe temperature, hydraulic pressure and force field changes induced by freeze-thaw cycling and subsequent physical phenomena such as expansion and settlement; they also provided a numerical simulation for the onedimensional problem [13]. Bronfenbrener described heat and matter transfer in a fine grain porous medium with frost heave during a phase transition and provided a model for the problem with a movement boundary condition. Comparison with test data proved that within a certain level of precision, the model was viable for frost heave estimation [14]. Yin created a seasonal permafrost region, subgrade soil, multi-factor, frost heave rate forecast model via field measurements and theoretical analysis and applied it to a project [15].

In this paper, based on a field survey in a permafrost region and high-speed railway subgrade filler and frost heave characteristics, the concept of subgrade microheave filler is proposed. A frost heave calculation formula for a microheave filler in closed systems is deduced via an indoor test and theoretical analysis. A frost heave deformation analysis model for microheave filler is created, and its effectiveness is proven.

## **2. Experimental study on microheave filler frost heave influencing factors**

Upon conducting an experimental study, Wang et al. suggested that there were three categories of railway subgrade filler: over coarse grained soils, coarse grained soils and fine grain soils [16]. In this paper, the large amounts of coarse grained soil filler in high-speed railway subgrades in the seasonal permafrost region of China are called microheave filler.

The bed filler used in high-speed railway subgrades in the permafrost regions of China is arranged as follows. A normal embankment bed surface is filled with a layer of 55-cm grading gravel, below which are 5 cm of thick coarse sand and 2.1 m of thick soil in two groups, A and B. In the frozen depth range, the embankment bed is filled with non-frost-heave soil in groups A and B, and soils in groups A, B and C exist below the beds. The top 1.0 m of the embankment bed floor is filled with nonfrost-heave filler in groups A and B. Based on the distribution of filler along the line, the lower sections have filler in groups A and B. Low embankment bed surfaces are filled with grading gravel. Non-frost-heave filler in groups A and B is used in the range of the upper meter of bed floors. The lower sections are filled with filler in groups A and B. In the bed floor lower sections, the grading gravel layer water content is 3.2–5.9%, and the fine grain content is 3.2–10.7%. In lower sections, the non-frost-heave soil filler water content generally is 3.7–9.2%, and the fine grain content is 0.4–9.3%. In seasonal permafrost regions, the entire beds are excavated and replaced. The bed surfaces are filled with grading gravel, the upper 1 m of the bed floors are filled with non-frost-heave filler in groups A and B, and the lower sections are filled with filler in groups A and B. The grading gravel layer water contents are 2.2–3.2%, the fine grain contents are 8.0–15.1%, the water contents in the lower section non-frost-heave soil filler are generally 3.7–9.2%, and the fine grain contents are 10.9–16.9%.

Coarse grained soil frost heave tests and analysis proved that the factors that influence major coarse grained soil frost heave include the soil property, water content, temperature and load [17]. To investigate the characteristics of high-speed railway subgrade filler frost heave in permafrost regions, in this chapter, typical permafrost region subgrade soil samples were selected to perform soil property tests for filler covering water content, liquid plastic limit and grain analysis. On this basis, the effects of various factors on filler frost heave were analyzed to obtain rules regarding the influence of soil fine grain content, compactness, water content, permeability and coarse grain pore filling by fine grains on the properties of coarse grained soil frost heave. It is worth noting that the test reported in this section was based on the conventional liquid and plastic limit combined determination method. In the test, fine grain soil liquid limit water and plastic limit water contents were measured to calculate the soil plasticity index and liquid index, which were used as a basis to evaluate the properties of filler soils. A standard screening test was employed to calculate the relative content of each grain group and to determine soil grain composition. In addition, for subgrades, compactness is not only a control index that ensures subgrade filling quality but also a major factor that affects the properties of filler frost heave. Under identical conditions, as compactness increases, fine grain soil frost heave increases initially and then decreases.

**3.2 Test method**

**3.3 Test items**

frost heave.

**Table 1.** *Test filler grades.*

**97**

bator, and the water contents were measured.

19.2%, and the optimal water content *ω<sup>0</sup>* was 13.2%.

study was conducted to investigate the following aspects.

Proper amounts of dry soil samples were mixed with water to produce the required water contents. The soil samples were separated into layers of predefined compactness (5 layers, each with thicknesses of 3 cm) and placed in the specimen box. The specimen box with a sample was placed in the incubator. Thermistor thermometers were deployed on the specimen top plate, bottom plate and side. The specimen box was wrapped in 5 cm of thick plastic foam for heat insulation. The top plate and bottom plate temperatures were controlled using two high precision low temperature circulation cooling systems. A dial indicator was installed on the top plate to monitor specimen deformation. Finally, the temperatures for the specimens were collected automatically via the data collector. The testing was performed in a closed environment. The unidirectional freezing method was applied [18], the duration of the freezing process for each specimen was 72 h, and the direction of freezing was from top to bottom. At the beginning of the tests, the soil column temperature was stabilized at approximately 1°C and maintained for 6 h. The bottom plate temperature was then maintained at 1°C. At 0.5 h, the top plate temperature was decreased to 15°C, and the soil samples were frozen rapidly from the top surface. The top plate temperature was increased to 2°C, and top plate temperature was then decreased by a certain amount per hour. At the conclusion of each test, the soil samples were separated into layers in the low temperature incu-

*Frost Heave Deformation Analysis Model for Microheave Filler*

*DOI: http://dx.doi.org/10.5772/intechopen.82575*

Test filler was obtained from the subgrade filling soil of a high-speed railway in Northeast China. The grades are listed in **Table 1**. The filler plastic limit *ω<sup>p</sup>* was

To investigate the effects of factors such as water content, filler and external load on microheave filler frost heave for this paper, a frost heave experimental

1. Effects of filler plastic limit and optimal water content on microheave filler

Proper amounts of dry filler were mixed with various amounts of water to produce 30 groups of ω specimens with various levels of initial water content. The initial water content values of the 30 groups of specimens are listed in **Table 2**. The

**Grain size range (mm) content (%)** 31.5–45.0 20 22.4–31.5 10 7.1–22.4 25 1.7–7.1 20 0.5–1.7 10 0.1–0.5 9 0.075–0.1 3 <0.075 3
