Keywords

1 Introduction

With the increasing number of new and expanded civil airports in China, the available land resources are becoming increasingly tense [1]. More airports choose to be built in mountainous valleys, crisscrossed areas and other harsh geographical environments, and a large number of high fill slope projects have appeared [2]. The settlement and uneven settlement of high fill slope engineering will occur after the completion of the project, which will seriously affect the safety of people’s lives and property [3, 4]. Therefore, it is necessary to explore the material properties of different regions in depth. Based on the actual project, this paper determines the engineering geological conditions of the study area through engineering investigation, and calibrates the material parameters in the indoor screening test, stone wear and liquid-plastic limit test, and saturated water absorption test, laying the material parameter foundation for subsequent research.

2 Overview of Engineering Geological Conditions

A proposed airport is intended to be a dual-use facility for both military and civilian purposes, with a total area exceeding over 4,000 acres. The construction standards for the airport are based on the design of a feeder airport with an annual passenger capacity of one million and an annual cargo capacity of 4,000 tons. The airport plans to construct a runway measuring 2800 m × 45 m, with a designed shoulder width of 1.5 m. Additionally, blast pads measuring 60 m × 48 m will be situated at each end of the runway to prevent damage from jet blasts. The airport’s flight area will be constructed to meet Grade 4C standards, with dimensions for the clearway set at 2920 m × 300 m and dimensions for the safety areas at the ends of the runway set at 240 m × 90 m. The site elevation, based on the 1985 National Elevation Datum, is preliminarily established at 165 m. Finite Element Model Establishment.

3 Construction Site Sampling

The samples are taken from the field project, and the selection results of different positions are quite different. In order to make the collected soil samples represent the real soil as much as possible, the soil samples are collected as much as possible at each position to avoid the influence of uneven selection on the test results. After the soil samples are transported back to the laboratory, they are uniformly mixed and tested. This sampling 1t. The acquisition process is shown in Fig. 1.

Fig. 1.
figure 1

The acquisition process

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4 Tests and Results

4.1 Indoor Screening Test

Referring to the ‘Highway Soil Test Procedure’ screening test procedure, the pore size (mm) of the coarse sieve (round hole) is selected as: 60, 40, 20, 10, 5, 2; the pore size (mm) of fine sieve was 2.0, 1.0, 0.5, 0.25, 0.075. The total soil mass before screening was 10,000 g, and the soil mass less than 2 mm was 710 g, and the soil less than 2 mm accounted for 7.1% of the total soil mass. The remaining records are shown in Table 1.

Table 1. The remaining records
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When the content of particles exceeding the particle size is greater than 5%, the equal mass substitution method is adopted. The method is to replace the content of super-diameter particles with equal mass according to all the coarse materials allowed by the instrument (from coarse materials with a particle size of 5 mm to the maximum particle size). The new gradation composition can be calculated according to the following formula. The calculation results are shown in Table 2:

$$ p_i = \frac{100 - p_m }{{p_m - p_5 }}\left( {p_{0i} - p_5 } \right) + p_{0i} $$
(1)
Table 2. The calculation results
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According to the coarse particle screening record (conversion algorithm), the filler particle gradation curve is drawn, as shown in Fig. 2.

Fig. 2.
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The acquisition process

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From the above Fig., the 0–5 mm gradation line is smooth, the particle size is continuous, and the slope is slow. The curve of 5–20 mm began to steep, and the particle content was the most, about from 14% to 63%. The steepness of the 20–60 mm line segment is slightly reduced. After calculation, the non-uniformity coefficient Cu is 6.172; the curvature coefficient Cc is 1.51, which meets the requirements of Cu ≥ 5 and 1 ≤ Cc ≤ 3, and the gradation is good.

5 Stone Abrasion and Liquid Limit, Plastic Limit

Referring to the ‘Highway Geotechnical Test Procedures’ joint determination method of liquid limit and plastic limit, representative samples were taken from coarse materials (particle size greater than 5 mm) and fine materials (particle size less than 0.5 mm) for stone wear and physical properties tests such as liquid limit and plastic limit. The experimental process is shown in Fig. 3, and the experimental results are shown in Table 3.

Fig. 3.
figure 3

Stone wear and liquid plastic limit test

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Table 3. Test results of stone wear and liquid plastic limit
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6 Saturated Water Absorption Test

Refer to the ‘Highway Geotechnical Test Procedures’ standard hygroscopic moisture content, the saturated water absorption rate of granular materials with particle sizes of 0–0.5 mm, 0.5–5 mm, and 5–40 mm is determined by grading. HT-30 saturated surface dry mold test instrument is selected for fine materials of 0–0.5 mm, and 101A-3 electric hot blast constant temperature drying box is selected for coarse materials of 0.5–40 mm. After drying, soak until the water absorption is saturated, then wipe the surface dry, and then weigh the wet mass. The saturated water absorption is:

$$ w_a = \frac{(m - m_s )}{{m_s }} \times 100 $$
(2)

The test results are shown in Table 4.

Table 4. Saturated water absorption test results
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7 Conclusion

Through the construction site sampling and indoor screening test, the calculated non-uniformity coefficient Cu is 6.172, and the curvature coefficient Cc is 1.51, which meets the good grading requirements of Cu ≥ 5 and 1 ≤ Cc ≤ 3, and the grading is good. Through the soil sample parameter test, the stone wear value of coarse material (particle size greater than 5 mm) is 27.4%, the liquid limit of fine material (particle size less than 0.5 mm) is 23%, and the plastic limit is 14%. The saturated water absorption rate of coarse material (5–60 mm) is 2.2%, the saturated water absorption rate of coarse material (0.5–5 mm) is 3.0%, and the saturated water absorption rate of fine material (0–0.5 mm) is 5.7%.