阅读说明：本技术 一种煤矸石复垦场土壤含水率检测方法 (Method for detecting soil moisture content of coal gangue reclamation farm ) 是由 郭亚超 康向南 雷永超 任予鑫 杨恒 吴宜珊 单成方 杜昭 李晓彤 李响 杨旭 于 2021-09-07 设计创作，主要内容包括：本发明公开一种煤矸石复垦场土壤含水率检测方法,涉及土地复垦与生态修复技术领域,旨在提出一种土壤含水率高效、快速检测方法,通过在煤矸石复垦场雷达测线的不同深度覆土中预埋“铝锭”,然后利用探地雷达获取并计算经过“铝锭”时反射的电磁波速,并采用水分传感器法探测“铝锭”所处层位土壤含水率,建立雷达电磁波速与土壤含水率间的关系模型,进而测算出矸石复垦场覆土层不同层位土壤含水率的分布,最后采用插值法得到复垦地含水率空间分布图,实现对复垦场地土壤含水率连续、高效探测,提高测量评估效率,具有较强的适应性和推广性。(The invention discloses a coal gangue reclamation field soil moisture content detection method, relates to the technical field of land reclamation and ecological restoration, and aims to provide a method for efficiently and quickly detecting the moisture content of soil.)

1. A method for detecting the water content of coal gangue reclamation farm soil comprises the following steps:

s1: determining the positions of radar survey lines (2) according to the area of the coal gangue reclamation field (1), and embedding a reflecting medium (3) in a soil covering layer (5) according to the position of each radar survey line (2);

s2: detecting each radar survey line (2) of the coal gangue reclamation land by using a ground penetrating radar (4);

s3: preprocessing the acquired radar data and calculating the radar wave speed;

s4: detecting the water content of the soil at different buried depths of the reflecting medium (3) on the section of one radar measuring line (2), taking an average value as the water content of the depth, and fitting the radar wave velocity and the water content to obtain a soil water content inversion model;

s5: and (3) obtaining the water content of each layer of soil in the reclamation area by utilizing a soil water content inversion model and combining with the wave speed of other survey line radars in the reclamation area, and obtaining a spatial distribution map of the water content of the coal gangue reclamation field (1) by utilizing an interpolation method.

2. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in the step S1, the position of the radar survey line (2) is determined according to a five-point method.

3. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in the step S1, the length of the radar survey line (2) is not less than 10 m.

4. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in step S1, the reflective media (3) are embedded in the cover soil layer (5) in a step-like manner at equal intervals.

5. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in the step S1, the reflecting medium (3) is an aluminum ingot, the diameter of the aluminum ingot is 8-10 cm, the height of the aluminum ingot is 6-8 cm, and the horizontal distance is not less than 50cm when the aluminum ingot is pre-buried.

6. The method for detecting the water content in the soil in the coal gangue reclamation farm as recited in claim 1, wherein in the step S2, a ground penetrating radar (4) with a center frequency of 200-1000MHz is adopted.

7. The coal gangue reclamation farm soil water content detection method as recited in claim 1, wherein in the step S3, the preprocessing method comprises filtering, wavelet transformation, automatic gain control and background denoising.

8. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in the step S3, the radar wave velocity is calculated according to the following formula:

wherein: v₁Is the propagation velocity of radar waves in the layer 1 soil, S₁Is buried depth t of the 1 st layer of reflective medium (3)₁The time required for the radar wave to be transmitted from the earth surface and received after being reflected by the 1 st reflecting medium (3);

wherein: v_iIs the propagation velocity of radar waves in the i-th layer of soil, S_i-1Is buried depth t of the i-1 th layer of reflective medium (3)_iThe time required for the radar wave to be received after reflection from the transmission via the i-th reflecting medium (3), S_iIs the buried depth of the ith layer of reflecting medium (3), and x is the ratio of the buried depth of the ith layer of reflecting medium (3) to the buried depth of the (i-1) layer of reflecting medium (3).

9. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 1, wherein in the step S4: and detecting the water content of the soil with different buried depths of the reflecting medium (3) on one radar measuring line section by using a TDR method.

10. The method for detecting the soil moisture content in the coal gangue reclamation farm as recited in claim 9, wherein in the step S4: each depth was probed 3 times and the average was taken as the water cut for that depth.

Technical Field

The invention relates to the technical field of land reclamation and ecological restoration, in particular to a method for detecting the soil moisture content of a coal gangue reclamation field.

Background

The coal gangue has the characteristics of high temperature, spontaneous combustion and low nutrient. When the gangue is used as a reclamation matrix layer, the overlying soil layer also faces the problems of poor soil water holding capacity, deteriorated soil quality, low vegetation survival capacity and the like, the detection of the water content of the surface layer covering soil is carried out, and the timely irrigation of the overlying soil layer is carried out, so that the key for ensuring the reclamation effect is realized. The soil moisture content is used as a direct factor for evaluating the soil quality, measurement methods such as a traditional drying method and a moisture sensor method (TDR method for short) have the characteristics of large engineering quantity, large cost of manpower and material resources, damage to a soil structure, low efficiency, unsuitability for large-range detection and the like, and the ground penetrating radar is used as a novel detection technology and can continuously, quickly and efficiently detect underground targets according to different transmission capacities of electromagnetic waves in different underground medium interfaces and target bodies, but because the soil belongs to a single medium, the soil moisture content of different levels of soil cannot be directly detected by the ground penetrating radar.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for detecting the soil moisture content of a coal gangue reclamation site, and solves the problems that a large amount of manpower, material resources and low efficiency are consumed and the soil moisture content in a scale range cannot be obtained in the traditional drying method, TDR method and the like.

In order to achieve the technical purpose, the method for detecting the water content of the coal gangue reclamation farm soil comprises the following steps:

the method comprises the following steps: according to the design of the area size of a coal gangue reclamation site, determining the positions of radar survey lines according to a five-point method, and simultaneously embedding the reflection media in the soil covering layer at the position of each radar survey line according to a ratio x (x is the ratio of the burial depths of two adjacent reflection media) in the coal gangue reclamation process;

step two: detecting each radar survey line of the coal gangue reclamation land by using a ground penetrating radar;

step three: preprocessing the acquired radar data and calculating the radar wave speed;

step four: detecting the water content of the soil at different reflection medium burial depths on one radar measuring line section by using a TDR method, taking an average value as the water content of the depth, and fitting the radar wave velocity and the water content to obtain a soil water content inversion model;

step five: and (3) obtaining the water content of each layer of soil in the reclamation area by utilizing a soil water content inversion model and combining with the wave speed of other survey line radars in the reclamation area, and obtaining a reclamation land water content spatial distribution map by utilizing an interpolation method.

Further, the first step specifically includes: before reclamation, according to the area size of a designed coal gangue reclamation site, determining the position of a radar survey line according to a five-point method, namely respectively arranging one survey line in the southeast, the northwest and the east of the reclamation site according to the area of the reclamation site, determining the specific range according to characteristics of the reclamation site, and then embedding a reflection medium on each survey line, wherein the length of the radar survey line is not less than 10 m. Meanwhile, in the coal gangue reclamation process, reflecting media are embedded in a soil covering layer in a step-shaped manner at each radar survey line position according to a ratio x (x is the ratio of the embedding depths of two adjacent reflecting media); and receiving reflected electromagnetic waves of different layers according to the step shape so as to obtain the soil moisture content of different layers.

Further, the first step specifically includes: soil belongs to single medium, utilizes the unable different horizon soil moisture content of direct detection of ground penetrating radar, wants to survey different horizon soil moisture content, must arrange the reflection medium different in soil at each horizon, can replace with the different medium that is distinguished from soil: steel bars, iron blocks, aluminum blocks, etc.; considering that the underground is in a humid environment for a long time, iron blocks, steel bars and the like are easy to corrode and have large weight, aluminum ingots which are light in weight and difficult to corrode are selected as reflecting media, the diameter of each aluminum ingot is 8-10 cm, the height of each aluminum ingot is 6-8 cm, and the horizontal distance is not less than 50cm when the aluminum ingots are embedded.

Further, the second step specifically comprises: detecting a radar survey line of a reclamation gangue yard by adopting a ground penetrating radar with the central frequency of 200-plus 1000MHz to obtain radar data, wherein the radar data is mainly a reflected wave waveform; the transmitting antenna sends high-frequency short pulse electromagnetic waves into the ground in a directional mode, the electromagnetic waves are reflected when meeting a stratum or a target body with electrical property difference in the transmission process, and the receiving antenna receives reflected wave signals, digitalizes the reflected wave signals and records the reflected wave signals in the form of reflected wave waveforms by a computer.

Further, the third step specifically comprises: the preprocessing of the acquired radar data includes filtering, wavelet transformation, automatic gain control (AGC gain) and background denoising. The propagation speed of the ground penetrating radar waves in each soil layer can be calculated according to the following formula:wherein: v₁Is the propagation velocity of radar waves in the layer 1 soil, S₁Is the buried depth of the layer 1 reflective medium soil, t₁The time required for the ground penetrating radar waves to be transmitted from the ground surface and reflected by the 1 st reflecting medium and then received is saved; wherein: v_iIs the propagation velocity of radar waves in the i-th layer of soil, S_i-1The i-1 th layer of reflective medium is buried deep in soil, t_iThe time required for the radar wave to be received after reflection from the transmission medium i_iThe buried depth of the ith layer of reflective medium soil is shown, and x is the ratio of the buried depth of the ith layer of reflective medium soil to the buried depth of the ith-1 layer of reflective medium soil.

Further, the fourth step specifically includes: and detecting the water content of the soil at different aluminum ingot burying depths on one radar measuring line section by using TDR (time domain reflectometry), detecting for 3 times at each depth, taking the average value as the water content of the depth, and fitting the radar wave velocity and the water content to obtain a soil water content inversion model.

Further, the fifth step specifically comprises: and obtaining the water content of each layer of soil in the reclamation area by utilizing a soil water content inversion model and combining with the wave speed of other measuring line radars in the reclamation area, and simultaneously obtaining a reclamation land water content space distribution map by utilizing ArcGIS software to carry out an interpolation method.

The invention has the beneficial effects that: the method overcomes the difficulty in traditional monitoring, the aluminum ingots are pre-buried in different-depth soil covering of a radar survey line of the gangue reclamation field in a step shape, then the ground penetrating radar is used for obtaining the electromagnetic wave speed reflected when the aluminum ingots pass through, the soil moisture content of the layer where the aluminum ingots are located is detected by adopting a moisture sensor method, a relation model between the radar electromagnetic wave speed and the soil moisture content is established, the distribution of the soil moisture content of different layers of the soil covering of the gangue reclamation field is measured, and finally the spatial distribution map of the water content of the reclamation field is obtained by adopting an interpolation method. The method can realize the multiple detection of the water content of the soil in the waste rock reclamation farm, ensure the reliability of the detection result and meet the requirement of modern rapid measurement.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic view of a radar line layout of the present invention;

FIG. 3 is an inverse model of soil moisture content according to the present invention;

FIG. 4 is a water content distribution diagram of a land surface (0-25cm) of a reclamation site according to the present invention;

in the figure: 1-coal gangue reclamation ground, 2-radar survey line, 3-reflection medium, 4-ground penetrating radar, 5-soil covering layer and 6-gangue layer.

Detailed Description

An embodiment of the present invention will be described in detail with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

A large amount of gangue in a coal mine is accumulated, soil covering is needed after the surface of the gangue is leveled, and the reclamation effect is evaluated, and the coal gangue reclamation field soil moisture content detection method is adopted to detect the soil moisture content of the reclamation field for multiple times according to the technical flow shown in the figure 1.

1) According to the design data of the construction engineering of the reclamation land, the area of the coal gangue reclamation land is 1 km and 0.24km²The thickness of the covering soil is 1.0m, five radar measuring lines 2 are determined in the south, the south and the north of a coal gangue reclamation field according to a five-point method, the length of each radar measuring line 2 is 10m, meanwhile, in the process of reclaiming the coal gangue, 4 reflecting media 3 (adopting aluminum ingots) with the diameter of 10cm and the height of 8cm are embedded in a covering soil layer 5 at equal intervals according to the step shape at the position of each radar measuring line 2, the vertical interval of two adjacent embedded aluminum ingots is 25cm, and the horizontal interval is set to be 3 m. As shown in fig. 2.

2) Detecting each radar survey line 2 of the coal gangue reclamation farm 1 by adopting a ground penetrating radar 4 with the central frequency of 500MHz, and setting a time window of the ground penetrating radar to be 20 ns; and arranging one electrode at each position of each measuring line at intervals of 25cm, and arranging 40 electrodes in total to obtain radar data.

3) The obtained radar data is subjected to filtering, wavelet transformation, AGC gain and background denoising pretreatment, and the time required for receiving radar waves transmitted by the ground penetrating radar 4 on the 3# measuring line by the ground penetrating radar 4 after the radar waves are reflected by aluminum ingots with different depths is dependent on the time required by the ground penetrating radar 4The following steps are carried out: t is t₁＝1.00ns,t₂＝2.05ns,t₃＝3.12ns,t₄4.58ns, and calculating to obtain the radar wave velocity as: v. of₁＝5×10⁸m/s，v₂＝4.76×10⁸m/s，v₃＝4.67×10⁸m/s，v₄＝3.42×10⁸m/s。

4) Excavating a soil profile at the 2 position of the 3# radar measuring line, detecting the soil moisture content of different aluminum ingot burying depths (25cm, 50cm, 75cm and 100cm) by using TDR (time-dependent radar), measuring for 3 times at each point, taking an average value as the moisture content of the depth, and fitting the radar wave velocity and the soil moisture content to obtain a soil moisture content inversion model:

as shown in fig. 3.

5) And (3) obtaining the water content of each layer of soil in the reclamation area by utilizing a soil water content inversion model and combining with the wave velocity of other measuring line radars in the reclamation area, and simultaneously obtaining a distribution map of the water content of different depths in the reclamation area by utilizing an ArcGIS software interpolation method, as shown in figure 4.

TABLE 1 TDR survey 3# radar survey line different depth soil moisture content