Device for monitoring and identifying mountain torrent and debris flow and method for early warning of disasters

Abstract

A device for monitoring and identifying a mountain torrent and debris flow and a method for early warning of disasters relate to the technical field of debris flow protection. The device includes a computation device, sensors, an amplifier and an analog-to-digital converter. The sensors convert an acquired impact force signal into a digital signal by the amplifier and the analog-to-digital converter, and transmits the digital signal to the computation device. The computation device utilizes the digital signal to compute an energy coefficient of a liquid impact signal and a solid-liquid impact energy ratio, and a debris flow mode is monitored and identified in combination with a threshold range of the energy coefficient and a threshold range of the solid-liquid impact energy ratio. The device identifies the nature of the mountain torrent and debris flow through time-frequency analysis of an impact force signal generated by the debris flow to sensors.

Claims

1. A device for monitoring and identifying a debris flow, comprising a computation device, sensors, an amplifier, and an analog-to-digital converter, wherein the sensors acquire an impact force signal, from the debris flow the impact force signal being amplified by the amplifier and converted into a digital signal by the analog-to-digital converter, and the digital signal is transmitted to the computation device, the computation device utilizes the digital signal to compute an energy coefficient e.sub.l of a liquid impact signal of the debris flow and a solid-liquid impact energy ratio r.sub.sl, and a debris flow mode is monitored and identified in combination with a threshold range of the energy coefficient e.sub.l and a threshold range of the solid-liquid impact energy ratio r.sub.sl, wherein $r_{sl}=\frac{e_s}{e_l},$ $e_l=\frac{{\int }_{f_{la}}^{f_{\mathrm{lb}}}E\left(f\right)\mathrm{df}}{{\int }_0^{\infty }E\left(f\right)df},$ e.sub.s is an energy coefficient of a solid particle impact signal $e_s=\frac{{\int }_{f_{sa}}^{f_{sb}}E\left(f\right)df}{{\int }_0^{\infty }E\left(f\right)df},$ of the debris flow, wherein a feature frequency domain range of a mud impact signal of the debris flow is [f.sub.la,f.sub.lb], a feature frequency domain range of particle impact is [f.sub.sa, f.sub.sb], the feature frequency domain range of the mud impact signal and the feature frequency domain range of the particle impact are obtained by a field experiment or by monitoring data analysis, f.sub.la is a lower boundary value of the feature frequency domain range of the mud impact signal, f.sub.lb is an upper boundary value of the feature frequency domain range of the mud impact signal, f.sub.sa is a lower boundary value of the feature frequency domain range of the particle impact, f.sub.sb is an upper boundary value of the feature frequency domain range of the particle impact, and E(f) is an energy spectrum of the debris flow; wherein the debris flow mode is no impact and is marked as a first mode parameter when e.sub.l and r.sub.sl are not changed; the debris flow mode is a water flow and is marked as a second mode parameter when e.sub.l is greater than 0.98 and r.sub.sl is less than 5e-4; the debris flow mode is a mud flow and is marked as a third mode parameter when e.sub.l is greater than or equal to 0.95 and less than or equal to 0.98 and r.sub.sl is greater than or equal to 5e-4 and less than or equal to 5e-3; the debris flow mode is a debris flow and is marked as a fourth mode parameter when e.sub.l is greater than or equal to 0.65 and less than or equal to 0.95 and r.sub.sl is greater than or equal to 5e-2 and less or equal to 5e-3; the debris flow mode is a water-rock flow and is marked as a fifth mode parameter when e.sub.l is greater than or equal to 0.65 and less than or equal to 0.95 and r.sub.sl is greater than or equal to 5e-2 and less than or equal to 0.5; and the debris flow mode is a clastic flow and is marked as a sixth mode parameter when e.sub.l is less than 0.65, and r.sub.sl is greater than 1.0; wherein the computation device encodes the digital signal for transmission by a radio signal; wherein feature frequencies of the sensors are greater than 3 kHz; wherein the sensors comprise a first sensor, a second sensor and a third sensor, heights from the first sensor, the second sensor and the third sensor to an earth surface being 0.5h.sub.1, 0.7h.sub.2 and 0.8h.sub.3 respectively, h.sub.1 being a perennial flow depth of a detected and identified ground, h.sub.2 being a debris flow starting water depth of the detected and identified ground, and h.sub.3 being a maximum water depth of the detected and identified ground in nearly 10 years.

2. The device according to claim 1, wherein the feature frequency domain range of the mud impact signal is [0.05, 3], and the feature frequency domain range of the particle impact is [300, 600].

3. The device according to claim 1, wherein the sensors are cylinders having diameters ranging from 50 mm to 100 mm.

4. A method for early warning a mountain torrent and debris flow disaster utilizing the device of claim 3, comprising: mounting the first sensor, the second sensor and the third sensor in a debris flow trench, wherein stress surfaces of the sensors make forward contact with a debris flow to acquire the impact force signal, the computation device utilizes the digital signal to perform time-frequency analysis, and performs information encoding on mode parameters generated by the sensors, and early warning of the debris flow disaster is performed according to encoded information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a basic flow chart of impact signal energy based debris flow mode identification of the present invention.

(2) FIG. 2 is a structural schematic diagram of a principle of a device for monitoring and identifying a mountain torrent and debris flow of the present invention.

(3) FIG. 3 is a structural schematic diagram of a sensor of the device for monitoring and identifying a mountain torrent and debris flow of the present invention.

(4) FIG. 4 is a mounting diagram of the device for monitoring and identifying a mountain torrent and debris flow of the present invention.

(5) The figures show 1-sensor, 11-first sensor, 12-second sensor, 13-third sensor, 2-support column, 3-earth surface, 4-concrete, 5-rebar, 6-signal and power pipeline and 7-debris flow trench.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(6) The present invention is further described in detail below by means of embodiments and drawings. It should be understood that the particular embodiments described herein are merely used to explain the present invention, and are not used to limit the present invention. Those skilled in the art should is understand that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the structural idea and scope of use of the present invention, but these modifications and substitutions fall within the scope of protection of the present invention.

(7) An empirical mode analysis based device for monitoring and identifying a mountain torrent and debris flow and a method of early warning of disasters, which are based on an early warning system to identify the nature of the mountain torrent and debris flow through time-frequency analysis of an impact force signal, and the early warning system is an effective early warning method constructed on the basis of features of the method.

(8) A basic process for identifying a debris flow mode based on energy distribution of an impact signal in different frequency bands is shown in FIG. 1. Firstly, a digital time sequence signal of an impact force of the debris flow is obtained by means of a pressure sensor 1 and a monitoring device, empirical mode decomposition (EMD) is carried out on impact force signals in previous 2Δt second time periods every Δt seconds by means of a preprogrammed preprogram in a microprogrammed control unit (MCU) to obtain a plurality of empirical mode functions IMF.sub.j(t), (j=1, 2, 3 . . . n), and then Hilbert transform (HT) is carried out on the obtained empirical mode functions to obtain energy spectrum E(f) of the signals, an impact force frequency spectrum of a general debris flow is shown as low-frequency impact of mud and high-frequency impact of particles, and therefore, a feature frequency domain [f.sub.la, f.sub.lb] of a mud impact signal and a feature frequency domain [f.sub.sa, f.sub.sb] of particle impact may be obtained according to a distribution rule of the energy spectrum on the frequency domain, thereby obtaining an energy coefficient e.sub.l of a debris flow liquid impact signal and an energy coefficient e.sub.s of a solid particle impact signal in the time period:

(9) $e_l=\frac{{\int }_{f_{\mathrm{la}}}^{f_{lb}}E\left(f\right)\mathrm{df}}{{\int }_0^{\infty }E\left(f\right)df}$$e_s=\frac{{\int }_{f_{sa}}^{f_{sb}}E\left(f\right)df}{{\int }_0^{\infty }E\left(f\right)df}$

(10) so as to further obtain a solid-liquid impact spectrum energy ratio:

(11) $r_{sl}=\frac{e_s}{e_l}$

(12) In general, determination of the feature frequency domain of the debris flow impact signal may be obtained by means of a field experiment or by monitoring data analysis. When experimental conditions do not exist, empirical parameters, i.e., the feature frequency domain [0.05, 3] of the mud impact signal and the feature frequency domain [300, 600] of the particle impact, may be used.

(13) By means of computation of a monitoring system computation device, the energy coefficient e.sub.l of the liquid impact signal of the impact force signal of fluid in a debris flow trench and the solid-liquid impact energy ratio r.sub.sl are obtained every Δt time. Therefore, the mode and state of the debris flow in the trench are determined according to a threshold range shown in table 1. For example, when the energy coefficient e.sub.l of the liquid impact signal of the fluid is greater than 0.98 and the solid-liquid impact energy ratio r.sub.sl is less than 5e-4, the fluid in the trench is water.

(14) TABLE-US-00001 TABLE 1 Debris Flow Mode Identification Table State e.sub.l r.sub.sl Debris flow mode 0 — — No impact 1 >0.98 <5e−4 Water flow 2 0.95-0.98 5e−4-5e−3 Mud flow 3 0.65-0.95 5e−2-5e−3 Debris flow 4 5e−2-0.5 Water-rock flow 5 <0.65 >1.0 Clastic flow

(15) Necessary basic composition of the device of the present invention is shown in FIG. 2. The device mainly includes a computation device, sensors 1, an amplifier and an analog-to-digital converter, where the computation device, such as a micro control computer (MCU), mainly has the effects of acquiring, processing and analyzing signals, sending early warning information, controlling modules to work, etc. The 3 impact force sensors (a first sensor 11, a second sensor 12 and a third sensor 13) are used for acquiring debris flow impact signals at three different positions in space, the signals obtained by the sensors pass through the amplifier and the analog-to-digital converter, impact force models are converted into digital signals to be transmitted to the MCU, and in such a case, the MCU computes and analyzes the 3 signals by means of a preset program (computes an energy coefficient and an energy spectrum ratio and assigns debris flow mode parameters), analyzes debris flow disaster information according to the debris flow mode parameters of the three sensors, and sends early warning information codes (shown in Table 2) of the debris flow by means of a fifth generation (5G) signal terminal module. In order to ensure time precision, system time is obtained by means of a satellite timing module. A power supply may be supplied by means of any type of power supply module having an uninterruptible power supply (UPS) function.

(16) The basic structure and mounting of the pressure sensors are shown in FIG. 3, and the sensors are cylinders, one end of which serves as stress surfaces to directly face the debris flow. The sensors 1 are fixed on a support column 2, and the support column 2 is connected to a rebar 5 by means of a bottom steel plate and poured in concrete 4 located below an earth surface 3. The whole support column 2 is made of steel, and therefore, a feature frequency of the whole is vibration of the mounted and fixed pressure sensors and an auxiliary structure is remarkably greater than a signal frequency of an impact force of the debris flow (preferably greater than 3 kHz), and the pressure sensors and the auxiliary structure are waterproof and impact-resistant. Diameters d of the sensors 1 are not suitable for being too great or too small, and is generally suitable for ranging from 50 mm to 100 mm. Heights h between the mounted sensors and the earth surface are divided into three grades, and are determined mainly by investigating a perennial flow depth h.sub.1, a debris flow starting water depth h.sub.2 and a maximum water depth h.sub.3 in nearly 10 years. FIG. 4 is field mounting schematic diagram of the device. The heights between the first sensor 11, the second sensor 12 and the third sensor 13 and the earth surface are configured to be 0.5h.sub.1, 0.7h.sub.2 and 0.8h.sub.3 respectively. A power supply and communication line of the sensors 1 is laid by burying a signal and power pipeline 6, and other modules are integrated on an erecting rod at a safe distance beside the debris flow trench 7.

(17) TABLE-US-00002 TABLE 2 Debris Flow Disaster Early Warning Information Encoding Disaster early Sensor state parameters reference First Second Third information Encoding sensor sensor sensor warning X-0-0 0&1 0 0 None 1-0-1 1 0 1 Mountain torrent 1-1-0 1 1 0 levels 2 and 3 1-1-1 1 1 1 Mountain torrent level 1 2-0-0 2 0 0 Mud flow level 4 2-0-1 2 0 1 Mud flow level 2-1-0 2 1 0 3 2-1-1 2 1 1 Mud flow level 2-2-0 2 2 0 2 2-X-2 2 0&1 2 2-2-X 2 2 0&1 2-2-2 2 2 2 Mud flow level 1 3-X-X 3 0&1 0&1 Debris flow level 4 3-2-1 3 2 1 Debris flow 3-1-2 3 1 2 level 3 3-3-Y 3 3 0&1&2 Debris flow 3-Y-3 3 0&1&2 3 level 2 3-3-3 3 3 3 Debris flow 3-4-3 3 4 3 level 1 3-3-4 3 3 4 4-3-3 4 3 3 4-X-X 4 0&1 0&1 Water-rock flow level 4 4-2-1 4 2 1 Water-rock flow 4-1-2 4 1 2 level 3 4-4-Y 4 4 0&1&2 Water-rock flow 4-Y-1 4 0&1&2 4 level 2 4-3-4 4 3 4 Water-rock flow 4-4-3 4 4 3 level 1 3-4-4 3 4 4 4-4-4 4 4 4 5-V-V 5 — — Clastic flow

(18) & is expressed as “or”.

(19) What is described above is merely a preferred embodiment of the present invention but not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should fall within the scope of protection of the present invention.