1. A method of predicting the progress of deterioration of rock strength in a hydro-fluctuation belt during operation of a reservoir, the method comprising:

acquiring physical environment characteristics and chemical environment characteristics of a reservoir in one operating cycle;

obtaining a rock test block;

determining a drying time of an indoor wet-dry alternation test based on the physical environment characteristics;

determining equivalent time of the falling zone rock soaked in the reservoir water and the chemical solution, namely the wetting time of the indoor wet-dry alternation test; the chemical solution is configured based on the chemical environment characteristic;

placing the rock test block in the chemical solution, and performing an indoor wet-dry alternating test according to the wetting time and the drying time; after each wet-dry alternate action, carrying out a triaxial compression test on the rock test block, and obtaining mechanical parameters of the rock test block;

drawing a change curve of the mechanical parameters along with the increase of the wet-dry alternation times based on the change of the mechanical parameters of the rock test block and carrying out function fitting to obtain a functional relation between the mechanical parameters of the rock test block and the wet-dry alternation times;

and predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the reservoir operation period based on the functional relation.

2. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the specific steps of determining the drying time of the indoor wet-dry alternation test based on the physical environment characteristics are as follows:

determining equivalent time of the falling zone rock in a natural drying state and an indoor drying state, wherein the equivalent time is the drying time of an indoor wet-dry alternation test;

the condition of the indoor drying is determined based on the physical environmental characteristics.

3. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the physical environmental characteristics comprise reservoir water level, wind speed, air temperature, water pressure and hydro-fluctuation zone bank slope stress;

the chemical environmental characteristics include the type of ions contained in the reservoir water, the amount of ions contained in the reservoir water, and the pH.

4. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: and selecting a position which is in the same rock stratum with the rock in the hydro-fluctuation belt and is not subjected to the alternate action of reservoir water wetting and drying as the acquisition place of the rock test block.

5. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the rock test block is a cylindrical test sample, and the size is 50mm in diameter and 100mm in height.

6. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the chemical solution is comprehensively determined according to the ion type, the ion content and the pH value in the reservoir water.

7. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the evaluation indexes for determining the equivalent time of the rock in the hydro-fluctuation belt under the reservoir water soaking and the chemical solution soaking are the change of rock strength, the change of density, the change of elastic modulus and/or the change degree of porosity.

8. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 2, wherein: and determining the evaluation index of the equivalent time of the falling zone rock in the natural drying state and the indoor drying state as the weight change condition of the rock.

9. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: and the confining pressure of the triaxial compression test is determined according to the bank slope stress and the water pressure of the rock in the falling zone.

10. The method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir as claimed in claim 1, wherein: the mechanical parameters of the rock test block comprise an internal friction angle and cohesive force.

Background

The reservoir can store or discharge flood periodically after storing water, resulting in the periodic lifting of the water level and forming a hydro-fluctuation belt. Rock mass in the falling zone is in an environment with periodic wet-dry alternate change for a long time. The periodical wet-dry alternate action can cause the macroscopic mechanical strength of the bank slope rock mass to be deteriorated, so that the bank slope is deformed, and even the bank slope is destabilized and damaged by the existing engineering reinforcement measures. Therefore, the reservoir bank slope can be pertinently reinforced in advance by predicting the degradation process of the rock strength of the hydro-fluctuation belt in the reservoir operation period, and the bank slope instability is prevented.

At present, the method for evaluating the deterioration process of the rock strength of the hydro-fluctuation belt in the reservoir operation period is mainly a wet-dry alternative test of indoor rocks, but the test cannot strictly simulate the long-term soaking process and the natural drying process of a test piece, so that the obtained result is not representative. In addition, considering that the water level change of the reservoir is long in time, the simulation of the humidification and drying process under the action of reservoir water in a laboratory takes several years or even longer, and the efficiency is low.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a method for predicting the deterioration process of the rock strength of a hydro-fluctuation belt in the operation period of a reservoir, and solves at least one technical problem in the background technology.

(II) technical scheme

In order to achieve the purpose, the invention adopts the technical scheme that: a method of predicting the progression of deterioration in rock strength in a hydro-fluctuation belt during operation of a reservoir, the method comprising:

acquiring physical environment characteristics and chemical environment characteristics of a reservoir in one operating cycle;

obtaining a rock test block;

determining a drying time of an indoor wet-dry alternation test based on the physical environment characteristics;

determining equivalent time of the falling zone rock soaked in the reservoir water and the chemical solution, namely the wetting time of the indoor wet-dry alternation test; the chemical solution is configured based on the chemical environment characteristic;

placing the rock test block in the chemical solution, and performing an indoor wet-dry alternating test according to the wetting time and the drying time; after each wet-dry alternate action, carrying out a triaxial compression test on the rock test block, and obtaining mechanical parameters of the rock test block;

drawing a change curve of the mechanical parameters along with the increase of the wet-dry alternation times based on the change of the mechanical parameters of the rock test block and carrying out function fitting to obtain a functional relation between the mechanical parameters of the rock test block and the wet-dry alternation times;

and predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the reservoir operation period based on the functional relation.

Preferably, the specific steps of determining the drying time of the indoor wet-dry alternation test based on the physical environment characteristics are as follows:

determining equivalent time of the falling zone rock in a natural drying state and an indoor drying state, wherein the equivalent time is the drying time of an indoor wet-dry alternation test;

the condition of the indoor drying is determined based on the physical environmental characteristics;

preferably, the physical environmental characteristics comprise reservoir water level, wind speed, air temperature, water pressure and hydro-fluctuation zone bank slope stress;

the chemical environmental characteristics include the type of ions contained in the reservoir water, the amount of ions contained in the reservoir water, and the pH.

Preferably, the acquisition site of the rock test block is selected to be a position which is in the same rock stratum with the rock in the hydro-fluctuation belt and is not subjected to the alternate action of reservoir water and water.

Preferably, the rock test block is a cylindrical test sample, and the size is 50mm in diameter and 100mm in height.

Preferably, the chemical solution is comprehensively determined according to the ion type, the ion content and the pH value in the reservoir water;

preferably, the evaluation indexes for determining the equivalent time of the falling zone rock soaked in the reservoir water and soaked in the chemical solution are the change of rock strength, the change of density, the change of elastic modulus and/or the change degree of porosity;

preferably, the evaluation index for determining the equivalent time of the falling zone rock in the natural drying state and the indoor drying state is the weight change condition of the rock;

preferably, the confining pressure of the triaxial compression test is determined according to the bank slope stress and the water pressure of the rock in the hydro-fluctuation belt;

preferably, the mechanical parameters of the rock test block comprise an internal friction angle and a cohesion force.

(III) advantageous effects

The invention provides a method for predicting the deterioration process of rock strength of a hydro-fluctuation belt in a reservoir operation period, which has the following beneficial effects compared with the prior art:

according to the chemical environmental characteristics of the hydro-fluctuation belt of the reservoir, the chemical solution is configured to accelerate the corrosion action of the aqueous solution and the sandstone so as to simulate the long-term interaction of the reservoir water and the rock of the hydro-fluctuation belt, so that the time of an indoor simulation test is greatly shortened. Various physical and chemical environmental factors of the hydro-fluctuation belt are fully considered, the obtained result is more representative, and the hydro-fluctuation belt has high practical value. The evaluation on the degradation process of the hydro-fluctuation belt rocks can provide theoretical support for the evaluation on the stability of the bank slope of the hydro-fluctuation belt of the reservoir, and has higher practical significance.

Drawings

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

FIG. 1 is a flow chart of the present invention for predicting the deterioration process of the red sandstone intensity of the hydro-fluctuation belt in the reservoir operation period;

FIG. 2 is a photograph of a triaxial sample of rock;

FIG. 3 is a fitted curve of rock mechanics parameters with increasing number of wet-dry alternation.

Detailed description of the invention

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

At present, the evaluation means for the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir mainly comprises a wet-dry alternation test of indoor rocks, but the liquid for soaking the rocks in the test is mainly pure water, and the physical action and the chemical action of reservoir water are not considered. Meanwhile, considering that the water level change of the reservoir is long in time, the simulation of the humidification and drying process under the action of reservoir water in a laboratory takes several years or even longer, and therefore, finding a method for shortening the simulation test time is the key for improving the indoor test efficiency.

Most of the existing researches on the evaluation of the degradation process of the rock strength of the hydro-fluctuation belt in the reservoir operation period only consider the physical process of the wet-dry alternating action, but neglect the influence of the chemical action processes of ion exchange, hydration, corrosion and the like on the degradation of the macroscopic mechanical strength of the sandstone test piece caused by the interaction of the reservoir water solution and the sandstone water and rock, so the obtained results are not representative. Therefore, the method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the reservoir operation period is provided, the fineness of the indoor simulation reservoir water wet-dry alternation effect is improved to a great extent, the physical and chemical effects of the reservoir water are considered, the obtained result is accurate, and the method can be used for reference of actual engineering.

For better understanding of the above technical solutions, the following detailed descriptions will be provided in conjunction with the drawings and the detailed description of the embodiments:

as shown in the attached figure 1 of the specification, the method for predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the operation period of the reservoir comprises the following steps:

step 1: analyzing physical and chemical environmental characteristics of rocks in a hydro-fluctuation belt of the reservoir, and collecting the change conditions of different physical environmental characteristics and chemical environmental characteristics in one operation period of the reservoir;

the physical environmental characteristics comprise reservoir water level, wind speed, air temperature, water pressure, hydro-fluctuation zone bank slope stress and the like, the chemical environmental characteristics comprise ion type, content and PH value, and each parameter can be an average value in a reservoir operation period.

Step 2: obtaining a rock test block from the site and processing the rock test block into a triaxial test standard sample by means of drilling, grinding and the like;

the rock test block obtained from the site is not positioned in the hydro-fluctuation belt, and the rock which is positioned in the same rock stratum with the hydro-fluctuation belt and is not subjected to the alternate action of reservoir water and humidity is selected as a sampling object.

Specifically, the triaxial standard sample has a height of 100mm and a diameter of 50mm, and is a cylindrical sample.

And step 3: determining a drying time of an indoor wet-dry alternation test based on the physical environment characteristics;

specifically, determining equivalent time of the falling zone rock in a long-term natural drying state and an indoor short-time drying state, namely determining the drying time of an indoor wet-dry alternation test;

according to the physical environment of the hydro-fluctuation belt obtained in the step 1, the main factors comprise temperature and wind speed, the soaked triaxial rock sample is placed in a drying box for drying, the temperature is set as the annual average air temperature of the location of the hydro-fluctuation belt of the reservoir, the wind speed is set as the annual average air temperature of the location of the hydro-fluctuation belt of the reservoir, the sample is taken out and weighed after a period of time, and when the weight of the sample is not changed any more, the time at the moment is taken as the drying time of an indoor wet-dry alternation test;

and 4, step 4: configuring a chemical solution for accelerating the degradation process of the rock strength of the hydro-fluctuation belt indoors according to the chemical environment characteristic information obtained in the step 1;

the chemical solution for accelerating the degradation process of the rock strength of the hydro-fluctuation belt indoors is determined according to different physical environment characteristics and chemical environment characteristics in one operation period of the reservoir obtained in the step 1, the type of reservoir water ions is mainly considered when the chemical solution is prepared, the corrosion of the chemical solution to the rock can be accelerated by adopting a method for expanding the concentration of the reservoir water ions by a certain multiple, so that the purpose of shortening the indoor wet-dry alternate humidification time is achieved, the chemical solution prepared indoors is comprehensively determined according to the type, the content and the pH value of the main ions in the reservoir water under the condition of comprehensively considering the charge balance of the solution, and the cation type of the chemical solution is preferably considered;

and 5: determining equivalent time of the falling zone rock soaked in the reservoir water for a long time and chemical solution prepared in the room for a short time, namely determining the humidification time of the indoor wet-dry alternation test;

putting the rock test block obtained in the step 2 into storage water for soaking, wherein the soaking time of the test sample in the storage water is the soaking time of the falling zone rock in the storage water within one reservoir operation period, and testing the porosity change value after the rock test block is dried after soaking is completed; and then, putting a fresh rock test block into the prepared chemical solution for soaking, taking out the test block at regular intervals, air-drying the test block to test the porosity change value, and taking the soaking time of the test block in the chemical solution as the humidification time of the indoor wet-dry alternation test when the porosity change of the test block soaked in the chemical solution is equal to the porosity change value of the test block soaked in the reservoir water.

Wherein the fresh rock test block is an un-soaked rock test block; further, in addition to measuring the change in porosity, the change in wave velocity, intensity and/or density may also be measured.

Step 6: placing the falling zone rock in an indoor wet-dry alternating environment, determining the humidifying time and the drying time according to the step 5 and the step 3 respectively, wherein the soaking solution used in the humidifying process is the chemical solution prepared in the step 4, and performing a triaxial compression test on the falling zone rock after each wet-dry alternating action;

and (3) comprehensively determining the confining pressure of the triaxial compression test according to the bank slope stress and the water pressure obtained in the step (1).

And 7: according to the change of the mechanical parameters of the falling zone rock after the indoor wet-dry alternating action, drawing a change curve of the mechanical parameters along with the increase of the wet-dry alternating times, and performing function fitting to obtain a functional relation between the mechanical parameters of the falling zone rock and the wet-dry alternating action times;

and 8: and predicting the deterioration process of the rock strength of the hydro-fluctuation belt in the reservoir operation period according to the functional relation between the mechanical parameters of the hydro-fluctuation belt rock and the wet-dry alternate action times.

And 7, inputting the expected reservoir operation cycle to obtain the mechanical parameter value of the rock after the reservoir operates the cycle, and referring to the subsequent reservoir bank slope hydro-fluctuation belt reinforcement design.

It should be noted that, in the above steps 1 to 8, other steps may be adopted in the specific implementation process, for example, the wetting time may be determined first, and then the drying time may be determined; or the rock test block can be obtained firstly, and then the physical and chemical environmental characteristics are collected.

According to the embodiment of the invention, the chemical solution is configured to accelerate the corrosion action of the aqueous solution and the sandstone according to the chemical environmental characteristics of the hydro-fluctuation belt of the reservoir so as to simulate the long-term interaction between the reservoir water and the rock of the hydro-fluctuation belt, so that the time of an indoor simulation test is greatly shortened. Various physical and chemical environmental factors of the hydro-fluctuation belt are fully considered, the obtained result is more representative, and the hydro-fluctuation belt has high practical value. The evaluation on the degradation process of the hydro-fluctuation belt rocks can provide theoretical support for the evaluation on the stability of the bank slope of the hydro-fluctuation belt of the reservoir, and has higher practical significance.

The following detailed description is given with reference to specific examples:

s1: the operation period of a certain reservoir is 1 year, the variation amplitude of the water level of the hydro-fluctuation belt of the bank slope in 1 operation period is 20m, the hydro-fluctuation belt rock mass is in the reservoir water immersion environment for 6 months every year, the hydro-fluctuation belt rock mass is in the direct sunlight environment for 6 months, the annual average temperature of the location of the reservoir is 26 ℃, the annual average wind speed is 2m/s, the stress of the rock bank slope is 1.8MPa, and the maximum water pressure is 0.2MPa, and the measured calcium ion concentration, the potassium ion concentration, the sodium ion concentration, the magnesium ion concentration, the chloride ion concentration, the sulfate ion concentration and the pH value of the reservoir water in one operation period are respectively 1mmol/L, 0.05mmol/L, 0.4mmol/L and 0.3mmol/L respectively.

S2: obtaining a rock test block from the site and processing the rock test block into a triaxial test standard sample by means of drilling, grinding and the like, as shown in the attached figure 2 of the specification;

s3: the concentration of main ions in the reservoir water is expanded by 50 times to prepare a water chemical solution, the priority of the ions is calcium ions, magnesium ions, potassium ions and sodium ions, the charge balance is comprehensively considered, and the finally determined chemical solution component is CaCl₂50mmol/L，Na₂SO₄ 10mmol/L，MgSO₄ 10mmol/L，KCl 2.5mmol/L。

S4: and (3) soaking the triaxial sample processed in the S2 in reservoir water for 6 months, taking out the triaxial sample after 6 months, air-drying the triaxial sample, measuring the porosity change of the triaxial sample to be 0.8%, soaking the fresh standard sample in a chemical solution prepared in a room again, and finding that the porosity change is 0.8% after soaking for 3 days, namely taking 3 days as the humidification time of the indoor wet-dry alternation test.

S5: and (3) putting the soaked rock triaxial sample into a drying box for drying, setting the temperature to be 26 ℃, setting the wind speed to be 2m/s, taking out the sample at intervals, weighing, and taking 6 hours as the drying time of the indoor wet-dry alternation test, wherein the mass of the rock does not change after 6 hours.

S6: and (3) putting the triaxial standard sample into a prepared chemical solution for carrying out wet-dry alternate action, wherein the wetting time is 3 days, and the drying time is 6 hours.

S7: taking a rock sample out after each wet-dry alternating action to carry out a triaxial test, taking 2MPa of confining pressure according to the maximum value of the sum of the bank slope stress and the water pressure, and finally determining the confining pressure of the triaxial test to be equal-difference seriesObtaining variation curves of mechanical parameters of the hydro-fluctuation belt rock along with the increase of the wet-dry alternation times at 0MPa, 2MPa and 4MPa, and obtaining the functional relations of the cohesive force, the internal friction angle and the reservoir running time respectively C by fitting the curves as shown in the attached figure 3 of the specification_n=7.20exp(-n/1.78)+7.44、

S8: and (3) predicting the change condition of the mechanical parameters of the rocks after the reservoir operates for 20 periods, and substituting n-20 into a functional relation to obtain that the cohesive force of the rocks in the hydro-fluctuation belt after the reservoir operates for 20 periods is 7.44MPa and the internal friction angle is 44.79 degrees.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.