River underground water level space-time evolution rule characterization method

Abstract

The invention discloses a river-side underground water level space-time evolution rule characterization method, and belongs to the technical field of underground water engineering. The method comprises the following steps: firstly, establishing an underground water burial depth fitting formula by considering factors such as a confined water head, river water level change, rainfall intensity and a distance between an observation point and a river side edge; then, constructing a stratum numerical model of the river-adjacent region, carrying out simulation analysis on different working conditions to obtain pore water pressure of the bottom of the phreatic aquifer under different working conditions by taking a confined water head, a river water level variation and rainfall intensity as single variables, and calculating underground water burial depths under different working conditions; the confined water head, the river water level variable quantity, the rainfall intensity, the underground water burial depth and the distance between the observation point and the side edge of the river under all the working conditions are substituted into an underground water burial depth fitting formula for fitting, and all fitting parameters are obtained; and finally, calculating a correction coefficient, and correcting the underground water burial depth to obtain an underground water burial depth calculation formula. And according to a groundwater burial depth calculation formula, calculating the groundwater burial depth of each observation point at the same moment or at different moments at the same observation point in the river-adjacent region. According to the method, the underground water level prediction precision is improved, and the arrangement of monitoring wells and the number of times of manual underground water level measurement are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of groundwater engineering, and in particular is a method for characterizing the temporal and spatial evolution law of groundwater levels near a river. Background Art

[0002] For example, engineering projects such as foundation pits, roads, bridges, and tunnels inevitably face groundwater problems, especially those built near rivers, which are particularly affected by groundwater. There is a water exchange between groundwater and rivers, which is significantly affected by seasonal changes, resulting in significant seasonal fluctuations in groundwater levels. In the flood season, rivers recharge the groundwater system, while in the dry season, the groundwater system recharges the river. In addition, rainfall also has a significant impact on groundwater levels.

[0003] In order to ensure the safety and stability of various riverside projects, it is necessary to conduct in-depth research on the evolution law and characteristics of groundwater in the riverside, which will help optimize resource utilization efficiency and reduce the impact on the environment. The traditional method is to set up a large number of monitoring wells, regularly measure the groundwater level manually, and collect data for analysis, but it cannot capture the rapid changes in the groundwater level in a short period of time, and the groundwater level data may have a long time delay and cannot reflect the dynamic changes of the groundwater level in real time. Therefore, the present invention proposes a method for characterizing the spatiotemporal evolution law of groundwater levels in rivers, which aims to accurately capture the dynamic changes of groundwater levels by deeply analyzing the seasonal changes in groundwater levels, the influence of rainfall and other factors. Summary of the invention

[0004] In view of the deficiencies in the prior art, the technical problem that the present invention intends to solve is to provide a method for characterizing the temporal and spatial evolution laws of groundwater levels near a river.

[0005] The present invention solves the technical problem by adopting the following technical solution:

[0006] A method for characterizing the temporal and spatial evolution law of groundwater level near a river, characterized in that the method comprises the following steps:

[0007] Step 1: Establish the groundwater depth fitting formula:

[0008]

[0009] Where H1 is the groundwater depth, H2 is the pressure head, ΔH is the river water level change, Q is the rainfall intensity, D is the distance between the observation point and the river side, a, b, c, m, e, f, g, o, p, j, v and l are all fitting parameters;

[0010] Step 2: Construct a numerical model of the stratigraphic formation in the riverside area, simulate and analyze different working conditions, obtain the pore water pressure at the bottom of the phreatic aquifer under different working conditions with the confined water head, river water level change and rainfall intensity as single variables, and calculate the groundwater depth under different working conditions;

[0011]

[0012] Where h is the drilling depth, c is the distance from the bottom of the unconfined aquifer to the lower boundary of the model, u is the pore water pressure at the bottom of the unconfined aquifer, ρ is the density of water, and g is the acceleration of gravity;

[0013] The pressure head, river water level change, rainfall intensity, groundwater depth and the distance between the observation point and the river side under all working conditions are put into the groundwater depth fitting formula for fitting to obtain various fitting parameters;

[0014] Step 3: Calculate the correction coefficient, correct the groundwater depth, and obtain the groundwater depth calculation formula;

[0015]

[0016]

[0017] Where β is the correction coefficient, m is the number of observation points, n is the number of monitoring days, and Δh i is the ith groundwater depth deviation;

[0018] Step 4: According to the groundwater depth calculation formula, calculate the groundwater depth at each observation point in the riverside area at the same time or at the same observation point at different times, and obtain the groundwater level line of the riverside area that changes with time and space.

[0019] Furthermore, in the third step, multiple observation points are randomly selected in the riverside area to set up monitoring wells to collect the actual value of the groundwater depth; the actual values ​​of the pressure head, river water level change, and rainfall intensity are obtained, and the actual values ​​of the pressure head, river water level change, rainfall intensity, and the distance between the observation point and the side of the river are brought into the groundwater depth fitting formula to calculate the theoretical value of the groundwater depth; the actual value of the groundwater depth is subtracted from the theoretical value to obtain the groundwater depth deviation.

[0020] Furthermore, the operating conditions are divided into three categories. The first type of operating condition is that the pressure head is a fixed value, the rainfall intensity is zero, and the change in river water level is the variable; the second type of operating condition is that the change in river water level and the rainfall intensity are both zero, and the pressure head is the variable; the third type of operating condition is that the pressure head is a fixed value, the change in river water level is zero, and the rainfall intensity is the variable.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention considers many factors such as rainfall intensity, the distance between the observation point and the river side, proposes a groundwater depth fitting formula, and introduces a correction coefficient to fine-tune the fitting formula, thereby improving the groundwater level prediction accuracy. It effectively reduces the layout of monitoring wells and the number of manual groundwater level measurements, reducing the consumption of manpower and material resources. The groundwater level at the same observation point at different times can be predicted in time, and the groundwater level at different observation points at the same time can be predicted in space, thereby more accurately capturing the dynamic changes of the groundwater level. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The following is the overall flow chart;

[0024] Figure 2 This is a schematic diagram of drilling in the strata in the Linhe area;

[0025] Figure 3 This is a cross-sectional view of the numerical model of the Linhe area stratigraphic structure. DETAILED DESCRIPTION

[0026] Specific embodiments are given below in conjunction with the accompanying drawings. The specific embodiments are only used to introduce the technical solutions of the present invention in detail and are not intended to limit the protection scope of the present application.

[0027] The present invention provides a method for characterizing the temporal and spatial evolution law of groundwater level in a river (hereinafter referred to as method, see Figures 1 to 3 ), including the following steps:

[0028] Step 1: Considering factors such as pressure head, river water level change, rainfall intensity, and the distance between the observation point and the river side, establish the groundwater depth fitting formula of formula (1);

[0029]

[0030] Where H1 is the groundwater depth (m), H2 is the pressure head (m), ΔH is the change in river water level, that is, the difference between the river water level before and after the change (m), Q is the rainfall intensity (m / d), D is the distance between the observation point and the side of the river (m), and a, b, c, m, e, f, g, o, p, j, v and l are all fitting parameters.

[0031] Step 2: Construct a numerical model of the stratigraphic formation in the riverside area, simulate and analyze different working conditions based on the numerical model, and obtain the pore water pressure at the bottom of the phreatic aquifer under different working conditions; calculate the groundwater depth based on the pore water pressure at the bottom of the phreatic aquifer, and bring the pressure head, river water level change, rainfall intensity, groundwater depth and the distance between the observation point and the river side under all working conditions into the groundwater depth fitting formula for fitting, and obtain various fitting parameters;

[0032] Drill the riverside strata to extract soil; divide the strata according to the color and particle size of the soil, and determine the thickness of each stratum; determine the physical parameters of each stratum according to the "Standard for Geotechnical Test Methods", including natural density, cohesion, internal friction angle, permeability, deformation modulus, etc.; start from the river side along the river width, drill once at a certain distance, and take the average value of the physical parameters at all drilling positions in the same stratum. At the same time, measure the river width S1, the vertical distance S2 from the riverbed to the surface, and the river bank slope θ and other data, and use numerical simulation software such as ABAQUS to construct a numerical model of the strata in the riverside area.

[0033] The numerical model of the riverside formation is used to simulate and analyze different working conditions, and the pore water pressure u at the bottom of the phreatic aquifer under different working conditions is obtained. Then, the groundwater depth under different working conditions is calculated according to formula (2);

[0034]

[0035] Where h is the drilling depth, c is the distance from the bottom of the phreatic aquifer to the lower boundary of the model (m), and ρ is the density of water (kg / m 3 ), g is the acceleration due to gravity (m / s 2 );

[0036] The pressure head, river water level change, rainfall intensity, groundwater depth and the distance between the observation point and the river side under all working conditions are substituted into formula (1) for fitting, and the fitting parameters of formula (1) are obtained.

[0037] Among them, the phreatic aquifer refers to the first aquifer located below the surface with a permeability greater than 1m / d. The confined water head is measured on the confined aquifer. The confined aquifer refers to the aquifer with a permeability greater than 1m / d and meets the conditions of the aquifer other than the phreatic aquifer appearing below the surface.

[0038] The working conditions can be divided into three categories with the confined water head, river water level change and rainfall intensity as single variables. The first type of working condition: the confined water head is a fixed value, the rainfall intensity is zero, the river water level change is set to kδ1, and the river water level change is used as a variable for simulation to obtain the pore water pressure at the bottom of the phreatic aquifer under various working conditions; k is an integer, and δ1 is 0 to 5m.

[0039] The second type of working condition: the river water level change and rainfall intensity are both zero, the pressure head is set to kδ2, and the pressure head is used as a variable for simulation to obtain the pore water pressure at the bottom of the phreatic aquifer under various working conditions; among which, δ2 takes a value of 0 to 15m.

[0040] The third type of working condition: the pressure head is a fixed value, the change of river water level is zero, the rainfall intensity is set to kδ3, and the simulation is carried out with rainfall intensity as a variable to obtain the pore water pressure at the bottom of the phreatic aquifer under various working conditions; among which, δ3 takes a value of 0.001~0.05m / d.

[0041] Step 3: Calculate the correction coefficient, correct the groundwater depth, and obtain the groundwater depth calculation formula;

[0042] In order to reduce the deviation between the actual and theoretical values ​​of groundwater depth, 2 to 5 observation points are randomly selected in the riverside area, and groundwater level monitoring wells are laid out in accordance with the specification "Technical Planning for Groundwater Environmental Monitoring" to collect the actual value of groundwater depth; pressure head monitoring wells are set up in accordance with the specifications, and the pressure head is collected at the bottom of the well by a pressure water level gauge to obtain the actual value of the pressure head; a pressure water level gauge is placed on the riverbed to monitor the river water level, and the river water level monitoring value is subtracted from the initial water level to obtain the actual value of the river water level change; the rainfall intensity is measured with a photoelectric rain gauge to obtain the actual value of the rainfall intensity.

[0043] Substitute the actual values ​​of the pressure head, river water level change, rainfall intensity, and the distance between the observation point and the river side into the groundwater depth fitting formula of formula (1) to obtain the theoretical value of the groundwater depth; subtract the actual value of the groundwater depth from the theoretical value to obtain the groundwater depth deviation; calculate the correction coefficient β according to formula (3), and then multiply the fitting formula by the correction coefficient to obtain the groundwater depth calculation formula of formula (4);

[0044]

[0045] H1=β(a+bH2+cH2 2 )(m+eΔH+fΔH 2 )(g+oQ+pQ 2 )(j+vD+lD 2 ) (4)

[0046] Where m is the number of observation points, n is the number of monitoring days, and Δh i is the ith groundwater depth deviation.

[0047] Step 4: In actual application, the pressure head H2, river water level change ΔH and rainfall intensity Q at each observation point in the riverside area at the same time or at different times are substituted into formula (4) to calculate the groundwater depth at each observation point at the same time or at different times, thereby obtaining the groundwater level line of the riverside area that changes with time and space.

[0048] In order to more intuitively display the temporal and spatial evolution of groundwater levels in riverside areas, the groundwater depth at each observation point can be visualized in the form of cloud maps, curve graphs, etc.

[0049] Matters not covered by the present invention are applicable to the prior art.

Claims

1. A method for characterizing the temporal and spatial evolution of groundwater levels in rivers. It is characterized in that The method comprises the following steps: Step 1: Establish the groundwater depth fitting formula: In the formula, H 1 is the groundwater depth, H 2 is the pressure head, ΔH is the change in river water level, Q is the rainfall intensity, D is the distance between the observation point and the side of the river, and a, b, c, m, e, f, g, o, p, j, v and l are all fitting parameters; Step 2: Construct a numerical model of the stratigraphic formation in the riverside area, simulate and analyze different working conditions, obtain the pore water pressure at the bottom of the phreatic aquifer under different working conditions with the confined water head, river water level change and rainfall intensity as single variables, and calculate the groundwater depth under different working conditions; Where h is the drilling depth, c is the distance from the bottom of the unconfined aquifer to the lower boundary of the model, u is the pore water pressure at the bottom of the unconfined aquifer, ρ is the density of water, and g is the acceleration of gravity; The pressure head, river water level change, rainfall intensity, groundwater depth and the distance between the observation point and the river side under all working conditions are put into the groundwater depth fitting formula for fitting to obtain various fitting parameters; Step 3: Calculate the correction coefficient, correct the groundwater depth, and obtain the groundwater depth calculation formula; Where β is the correction coefficient, m is the number of observation points, n is the number of monitoring days, and Δh i is the ith groundwater depth deviation; Step 4: According to the groundwater depth calculation formula, calculate the groundwater depth at each observation point in the riverside area at the same time or at the same observation point at different times, and obtain the groundwater level line of the riverside area that changes with time and space.

2. The method for characterizing the temporal and spatial evolution of groundwater level in a river according to claim 1, It is characterized in that In the third step, multiple observation points are randomly selected in the riverside area to set up monitoring wells and collect the actual value of groundwater depth; the actual values ​​of pressure head, river water level change, and rainfall intensity are obtained, and the actual values ​​of pressure head, river water level change, rainfall intensity, and the distance between the observation point and the river side are brought into the groundwater depth fitting formula to calculate the theoretical value of groundwater depth; the actual value of groundwater depth is subtracted from the theoretical value to obtain the groundwater depth deviation.

3. The method for characterizing the temporal and spatial evolution of groundwater level in a river according to claim 1 or 2, It is characterized in that There are three types of operating conditions. The first type of operating condition is that the pressure head is a fixed value, the rainfall intensity is zero, and the change in river water level is the variable; the second type of operating condition is that the change in river water level and rainfall intensity are both zero, and the pressure head is the variable; the third type of operating condition is that the pressure head is a fixed value, the change in river water level is zero, and rainfall intensity is the variable.

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