Wang Tiehang Liu Mingzhen Lu Jie

(Shaanxi xi Xi University of Architecture and Technology School of Civil Engineering 7 10Q55)

According to the climatic characteristics of the loess plateau and the existing literature, the numerical value of surface temperature field simulating the climatic factors of the loess plateau is put forward.

Calculation method, and simulate the boundary conditions such as temperature, radiation and humidity. Through the analysis and study of the boundary factors of the Loess Plateau, the suitable

Model parameters of loess plateau. Through the comparative analysis of the calculated and measured results of the surface temperature in Xi and Yan 'an, it is shown that the surface temperature in this paper is within the range.

The rationality of this method is analyzed, and the dynamic change of temperature field of loess subgrade with climate is analyzed, and the influence of temperature gradient on the stability of unsaturated loess subgrade is discussed

Influence, indicating that the influence of day and night change of external conditions on subgrade and pavement temperature is less than 30 cm.

Numerical analysis of loess temperature and climate: roadbed

1 Introduction

Subgrade is directly affected by radiation, evaporation, humidity, wind speed and other gases.

Affected by climate factors and subgrade surface morphology, the soil temperature field is changing.

Yes Water content changes due to water migration caused by temperature change, and

It causes the freezing-thawing phase change of soil and makes water migrate to the freezing-thawing interface. Temperature change

It leads to the change of humidity field of engineering soil, and then leads to the change of strength field.

Chemical transformation (p 1) often leads to a series of diseases. Subgrade engineering intersection

The problem of temperature difference and the diseases caused by it, that is, the problem of yin and yang in engineering

Slope problems are mainly related to climatic factors such as radiation from shady and sunny slopes of subgrade.

About the difference between elements. At present, there are few research results in this field. This paper simulates

Climate Change Process and Subgrade Surface Morphology in Loess Plateau

The numerical calculation method of temperature field and the changing process of temperature field are given.

Discuss it.

2. Numerical model and parameter selection of loess subgrade temperature field.

Radiation, evaporation, humidity, wind speed and other factors change with time. yellow

The temperature field of soil subgrade belongs to unstable phase change temperature field, and its basic equation is

([K]+ (middle school) four ={P|t+ Yan Siyi Mountain (1)

Where [K] is the temperature stiffness matrix; [Ⅳ] is the time of unstable temperature change.

Array; {r} is the column vector of temperature value; △f is the time step; Combined {P}

In an array, the subscript f is time.

{P} is a comprehensive consideration of phase change, radiation, convection and evaporation.

Array. Radiation array includes solar radiation array, earth radiation array and large-scale radiation array.

Airborne radiation array. See related literature ∞ 1 for each array. Refer to related articles.

Given 1, the surface radiation blackness of loess is 0.68, and loess is taken.

The absorption rate of solar radiation on the surface is O.78, and asphalt pavement is harmful to the sun.

The radiation absorption rate is 0.90. Atmospheric radiation blackness z: and the earth to the atmosphere

The value of radiation absorption rate is complex, and its value is related to temperature and clouds.

Quantity, humidity, dust content and other factors, temperature and humidity can not only

To reflect the amount of water vapor in the air, but also reflect the level of cloud cover.

everywhere

In this paper, temperature and humidity are selected as the characteristic indexes of climate to determine Z:

After analysis with Lu:, consider that the product of Z: and Lu 7 in the calculation is

A whole, get the definite relationship of Z: Lu.

Z2 Lu' =，+0.006t+0.004SD (2)

Where z is the air temperature,' (℃); S is relative humidity, (%); factory

Boxing National Natural Science Foundation (50308024).

Wang Tiexing, male, professor.

In order to comprehensively consider the regional coefficient affected by other factors, Xi takes a value.

0.20, Yan 'an takes 0.25. Monthly average temperature in Xi and Yan 'an areas.

And relative humidity are shown in table 1

Table 1 temperature and relative humidity table

Taking the east-west subgrade as an example, the slope ratio of subgrade slope is 1: 1.5, according to

According to the method in reference [10], the south slope and north slope of subgrade are calculated.

See Table 2 for the slope.

Table 2 Table of Slope Coefficient of South Slope and North Slope

Wanfang Data

2. Subgrade Engineering, No.3, 2008 (totalNo. 138), is the national Chinese core periodical.

3 Calculation results and analysis

Using the above methods, the local climatic conditions in Xi 'an and Yan 'an are simulated.

The surface temperature is calculated, and the average surface temperature obtained by calculation and measurement varies with

The calculated results are in good agreement with the measured results.

Taking Xi 'an east-west embankment as an example, the temperature field of subgrade is studied.

Calculation and analysis. Slope ratio of subgrade slope 1: 1.5, width 10 m, height 4.

M, asphalt pavement. Calculate the daily average temperature of subgrade in different months.

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Figure 1 temperature distribution of subgrade shady slope with depth

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Fig. 2 Distribution of subgrade sunny slope temperature with depth

Figure 1 shows the distribution of average temperature on the surface of the shady slope of subgrade with depth; Figure 2 shows

Distribution of average temperature on sunny slope of subgrade with depth. The picture shows that no matter in the shade

Under the slope or sunny slope, the temperature distribution along the depth changes with the season.

The calculation shows that the average temperature of shallow soil in winter is low and the depth is 3 m.

There is an obvious temperature gradient at the depth of the shell. Due to the unsaturated soil water content

It has the characteristics of migration from high temperature area to low temperature area, and is made in temperature gradient.

In winter, soil moisture constantly migrates to the surface. Local topsoil freezing

At the time of joining, the continuously migrating water gradually freezes and appears in the frozen layer.

Frost heave, even permafrost. When the frozen layer melts in spring, it is solid.

A sharp drop in temperature can cause diseases such as slipping, or form a loose layer, which is easy.

Washed away by rain. In summer, the average temperature of shallow soil is higher, 3 m.

There is an obvious negative temperature gradient along the depth range, which has the following characteristics.

Inhibition of evaporation potential leads to the migration and evaporation of soil moisture to the surface.

Comparing figure 1 with figure 2, we can see the temperature difference between the shady slope and the sunny slope.

There is little difference in fabrics in summer, but there is a big difference in winter. The difference between summer solstice and winter solstice is the smallest.

The difference is the biggest. In winter, the temperature difference between sunny slope and shady slope is large, which is easy to frost.

In this way, different freezing states appear on the slopes of Yin and Yang. The picture shows Xi 'an.

The sunny slopes in this area are not frozen all year round, while the shady slopes are frozen in winter.

In the northern cold region of the Loess Plateau, there are differences in freezing depth.

question

Figure 3 shows the lateral temperature of subgrade at 2 meters and 4 meters below the road surface.

Degree distribution. As can be seen from the figure, the subgrade temperature in July is endothermic, and the more.

Near the slope, the higher the temperature, the greater the temperature gradient. 65438+ 10 month subgrade

The temperature is exothermic. The closer to the slope, the lower the temperature and the higher the temperature gradient.

It's huge. The lateral change of temperature in the middle of subgrade is small, but it increases with the increase of depth.

In addition, the temperature at 2 m depth in July is higher than that at 4 m depth. 65438+ October

The temperature at a depth of 2m is lower than that at a depth of 4m.

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Distance from the center /c "Distance from the center, cm"

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Fig. 3 transverse thermal distribution of subgrade

Dynamic change of temperature field of loess subgrade with climate, especially temperature.

Considering the influence of temperature, the existence of slope is very important to determine the permeability of unsaturated soil subgrade.

Coefficient, determine the unsaturated soil water potential, unsaturated soil subgrade water field.

Calculation is valuable.

The average daily temperature of subgrade is calculated and analyzed above. In order to enter

Further discuss the day-night difference of subgrade temperature, and divide a day into two time periods.

Do a calculation. Calculate the daytime average temperature distribution of subgrade and pavement and the road

Average temperature distribution of subgrade and pavement at night. The surface is directly exposed to the outside world day and night.

Conditions change, and the temperature difference between day and night is large. This difference varies with the seasons.

Different festivals, the biggest difference is in July, exceeding 30℃, and the highest is in 65438+ 10.

Small, about 7℃. But at a depth of 30 cm, the average temperature during the day

The average temperature at night is almost the same, with little difference. because

Therefore, the influence of day and night changes of external conditions on pavement temperature should not exceed.

30 cm. When the depth exceeds 30 cm, the external conditions can be ignored.

The influence of night change. When the depth is less than 30 cm, day and night contrast should be considered.

Wanfang Data

Zheng Jianlong et al. Field observation and analysis of expansive soil subgrade temperature 3.

Field observation, analysis and research on temperature of expansive soil subgrade

Zheng Jianlong Miao Wei

(School of Highway Engineering, Changsha University of Science and Technology, Changsha, Hunan 4 10076)

In order to study the variation law of ground temperature of expansive soil subgrade under natural climate conditions, experiments were carried out on expansive soil embankment.

After more than one year of on-site follow-up observation, the variation law of soil temperature with time at different positions was analyzed, and the phenomenon of temperature change lag at different depths was found.

The aftereffect and seasonal difference of temperature field distribution, and describe and explain its characteristics and reasons. According to the sign of temperature amplitude, infer

The serious influence depth of local expansive soil climate is analyzed, which can provide reference for related engineering treatment.

Keywords: in-situ observation of temperature of deep expansive soil affected by climate

1 preface

Expansive soil is a kind of clay mainly composed of hydrophilic mineral (montmorillonite)

Stone, illite) composed of high liquid limit clay, its main characteristics are as follows

Water absorption obviously swells and softens, and dehydration and cracking are severe. A large number of research forms

During the Ming and Qing Dynasties, the dry-wet cycle of climate caused the shallow damage of expansive soil subgrade.

The fundamental reason, therefore, the relationship between soil and water has become the focus of expansive soil research and

Hot spots, but not temperature, are also directly affected by climate.

Has attracted enough attention.

According to thermodynamic theory and unsaturated soil theory, temperature has a great influence on unsaturated soil.

And the nature of the soil. First of all, the suction of unsaturated soil is generally constant.

It means the free energy state of soil water, temperature rise and potential energy of soil water.

Increase, suction decreases, and shear strength decreases. Secondly, the soil is wet.

Temperature field and temperature field are coupled and influenced each other. In other words, the soil

The movement of soil moisture is not only caused by uneven distribution of water content.

Yes, the existence of temperature gradient is also the reason driving water migration. From this

It can be seen that the temperature of expansive soil subgrade under different climatic conditions is studied.

The law of change is of great theoretical and practical significance.

Meaning.

Science and technology project of western traffic construction of Ministry of Communications (2002 3 18000).

Zheng Jianlong, male, professor, doctor, doctoral supervisor.

2 Design and implementation of observation scheme

In the study of unsaturated soil temperature change law, poplar fruit

Lin et al. obtained the results of day and night water accumulation through the model test of expansive soil subgrade

Under four simulated climatic conditions of sunshine, cloudy day and rainfall, expansive soil subgrade

The law of temperature change has a long history. Liu Bingcheng and others, under various conditions, are not satisfied.

The dynamic characteristics of temperature and humidity distribution in porous soil were studied in laboratory.

The influence of temperature effect on water migration is analyzed through experimental research. for

In order to truly and accurately understand the expansive soil subgrade under natural climate conditions,

In this study, the variation law of soil temperature was studied by field tracking method.

Observe. The observation point is located in Ningming section of Nanyou (Guan Yi) Road.

Section Al(2+4 12) is located at the edge of geogrid reinforcement of this construction team.

Treatment scheme "in the experimental section, the width of grid package is 3. 0 m, with embankment

The filler is the weathered residual soil HJ of Ningming gray-black expansive shale, which is buried by * * * *.

The temperature sensor, water content probe, earth pressure box and horizontal displacement are introduced.

Six observation elements: instrument, section settlement tube and vertical inclinometer tube. that

In order to ensure the accuracy and stability of observation, Changsha Golden Code chose 3.

JMT-36 temperature sensor produced by high-tech company, its main technology

The indicators are: measuring range 1: 20- 1 10℃, accuracy +0.5℃, line.

Sex error +0.3℃. Seven temperature sensors are arranged along the transverse direction with an interval of.

The horizontal distance of the slope is 0.4 m, 0.9 m, 1.5 m, 2.2 m,

3.0m, 4.0m and13.0m, 3.5m away from the top of subgrade.

The temperature changes greatly. Because of its heat absorption, soil surface is less than asphalt pavement.

The change of subgrade temperature caused by the day-night change of boundary conditions is less than the reference value of asphalt pavement;

Surface, so we can consider the influence of day and night changes of external conditions on subgrade temperature [1 Wang Tiexing], Discussion on water migration of unsaturated loess under the influence of temperature and geotechnical force.

The sound does not exceed 30 cm. ⅲ Gail ='0,: ∑ Zhai:% Tadpole, W. Ferret. One ~. . . . . m .

Conclusion (33): 483-500.

Temperature change can lead to a series of diseases in loess subgrade, [3] Dang, Li Jing, Influence of water content on unsaturated loess strength, Journal of Northwest Agricultural University,

Especially the Yin-Yang slope and the diseases caused by it are mainly related to some new trends in the study of five studies in Ru Ru. Journal of Geotechnical Engineering, 200 1 year.

It is related to the difference of climate factors. This paper is based on Loess Plateau 23 (1): L- 13.

Climate characteristics and existing literature, put forward to simulate the climatic factors of the Loess Plateau [5] Liu Baojian' Zhi Xilan, Xie et al. Collapsibility analysis of loess in highway engineering

The numerical calculation method of surface temperature field is based on the simulation of temperature, radiation and [6]. Resist D qianren quick repair training

Humidity and other boundary conditions, through the analysis of the boundary factors of the Loess Plateau. Two cups of coffee for me: "Qi. Ghai-ibet. 1. withered lens. I ... H arrives at two e, 2002, 45.

The model parameters suitable for the loess plateau are determined. Re-discussion on Xi 'an (4): 433-"3.

Plastic chalk must be made, and the amount of bamboo knots must be repeated. Stupid words: My wife says Lotus is arrogant, but I swear to save the pot.

The rationality of the method in this paper, the calculation results of the east-west slope reveal that Gao Lan: salary: reputation? Hu Fanhua II; Numerical model of degree field. heavy

The difference of surface temperature between yin and yang slopes was analyzed, and the surface temperature of yin and yang slopes was studied. Journal of Qing University, 2003,26 (6): 66-69.

The variation law of this difference with seasons is discussed. External conditions [10] Numerical analysis of loess subgrade surface temperature simulated by Wang Tiexing and Yue Caikun. roadbed

The influence of diurnal variation on subgrade and pavement temperature is less than 30 cm.

Project-2008t (1):1also received: April 20, 2007.

Wanfang Data