**3.2 Test method**

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

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

basis to evaluate the properties of filler soils. A standard screening test was

**3. Microheave filler frost heave test**

**3.1 Test apparatus**

**Figure 1.**

**96**

*Frost heave test apparatus.*

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.

The frost heave test apparatus consisted of a specimen box, an incubator, a temperature control system, a temperature monitoring system, a deformation monitoring system, a pressure loading system and a water supply system, as shown in **Figure 1**. The specimen box had a diameter of 15 cm and a height of 15 cm.

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 incubator, and the water contents were measured.

### **3.3 Test items**

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

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 study was conducted to investigate the following aspects.

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

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


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


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

required amounts of the specimens were calculated based on a compactness of 0.95. The specimens were then compacted in the specimen box for frost heave testing.

To prepare specimens with the required filler contents, proper amounts of dry filler were mixed with the required filler. In addition, the specimen's filler volume

*V*<sup>1</sup> is the filler skeleton grain volume fraction, *V*<sup>2</sup> is the filler volume fraction, *M*<sup>1</sup> is the skeleton grain mass for a unit specimen volume, *γ*<sup>1</sup> is the skeleton grain dry density for the corresponding soil sample compactness, *M*<sup>2</sup> is the filler mass for a unit specimen volume, and *γ*<sup>2</sup> is the filler dry density for the corresponding soil

In this test, 15 groups of specimens were prepared. The specimen filler contents

contents were used to ensure that the filler skeleton component was proportionally adjusted under the premise that the total mass of filler remained unchanged. All the specimens used in the frost heave test had 15% water content and compactness

Filler frost heave and pure filler frost heave tests were performed for the 15 groups of filler content specimens prepared in (3) under test conditions of 15%

**specimen volumetric water content ωV(%)**

� 100% (1)

3. Effects of filler content and filling rate on microheave filler frost heave

*<sup>s</sup>* <sup>¼</sup> <sup>1</sup>‐*V*<sup>1</sup> *V*<sup>2</sup>

and filler filling rates are listed in **Table 4**. In the test, fillers with different

4. Effects of filler frost heave on microheave filler frost heave.

1 5.83 2 7.02 3 8.30 4 9.60 5 11.07 6 11.34 7 11.85 8 13.17 9 14.48 10 15.27 11 15.80 12 16.04 13 16.57 14 17.49 15 18.21

fill rate s was calculated via the following formula.

*Frost Heave Deformation Analysis Model for Microheave Filler*

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

, *<sup>V</sup>*<sup>2</sup> <sup>¼</sup> *<sup>M</sup>*<sup>2</sup> *γ*2 .

water content and 0.95 compactness [19].

where *<sup>V</sup>*<sup>1</sup> <sup>¼</sup> *<sup>M</sup>*<sup>1</sup>

sample compactness.

values of 0.95.

**Table 3.**

**99**

*Specimen volumetric water contents.*

*γ*1

**Table 2.** *Specimen initial water contents.*

first 15 groups of specimens were used to investigate the effects of filler plastic limit on the microheave filler frost heave property, and the next 15 groups of specimens were used to investigate the effects of filler optimal water content on the microheave filler frost heave property. The required amounts of the specimens were calculated based on a compactness of 0.95. The specimens were then compacted in the specimen box for frost heave testing.

2. Effects of volumetric water content on microheave filler frost heave

Proper amounts of dry filler were mixed with various amounts of water to produce 15 groups of *ω<sup>V</sup>* specimens with various levels of initial water content. The initial water content values of the 15 groups of specimens are listed in **Table 3**. The

required amounts of the specimens were calculated based on a compactness of 0.95. The specimens were then compacted in the specimen box for frost heave testing.

3. Effects of filler content and filling rate on microheave filler frost heave

To prepare specimens with the required filler contents, proper amounts of dry filler were mixed with the required filler. In addition, the specimen's filler volume fill rate s was calculated via the following formula.

$$s = \frac{1 \cdot V\_1}{V\_2} \times 100\% \tag{1}$$

where *<sup>V</sup>*<sup>1</sup> <sup>¼</sup> *<sup>M</sup>*<sup>1</sup> *γ*1 , *<sup>V</sup>*<sup>2</sup> <sup>¼</sup> *<sup>M</sup>*<sup>2</sup> *γ*2 .

*V*<sup>1</sup> is the filler skeleton grain volume fraction, *V*<sup>2</sup> is the filler volume fraction, *M*<sup>1</sup> is the skeleton grain mass for a unit specimen volume, *γ*<sup>1</sup> is the skeleton grain dry density for the corresponding soil sample compactness, *M*<sup>2</sup> is the filler mass for a unit specimen volume, and *γ*<sup>2</sup> is the filler dry density for the corresponding soil sample compactness.

In this test, 15 groups of specimens were prepared. The specimen filler contents and filler filling rates are listed in **Table 4**. In the test, fillers with different contents were used to ensure that the filler skeleton component was proportionally adjusted under the premise that the total mass of filler remained unchanged. All the specimens used in the frost heave test had 15% water content and compactness values of 0.95.

4. Effects of filler frost heave on microheave filler frost heave.

Filler frost heave and pure filler frost heave tests were performed for the 15 groups of filler content specimens prepared in (3) under test conditions of 15% water content and 0.95 compactness [19].

