Engaged in teaching and scientific research in seepage theory, groundwater numerical simulation, groundwater resources and environment evaluation and management. He presided over 38 national key science and technology projects (3 projects), National Natural Science Foundation projects (3 projects) and other scientific research projects, and won the first prize with the first author: 1 National Science and Technology Progress Award; 3 second prizes for provincial and ministerial level scientific and technological progress; Second prize of excellent teaching materials 1. He published 12 books and 100 papers. China Geo University 2 1 1 Project I and II "Geological Environment Protection and Geological Disaster Prevention" and "Groundwater Resources and Geological Environment Protection" are academic leaders and chief scientists.
Professor Chen Chongxi's major academic achievements are as follows:
1. Theoretical problems of groundwater resources evaluation
Evaluation of groundwater sustainable exploitation is one of the most important research directions of hydrology and water resources engineering. However, for a long time, groundwater recharge has been used as the evaluation basis at home and abroad. 1966 ~ 1978 Professor Chen Chongxi demonstrated: "The influence range caused by borehole pumping develops with time, because borehole pumping destroys the original hydrodynamic balance. If there is no increase in recharge or reduction in excretion due to pumping, the scope of influence will develop indefinitely. " At this time, all the groundwater extracted is stored; "Only when the sum of the increment of groundwater recharge and the decrement of groundwater discharge obtained by local pumping is equal to the pumping amount, can the groundwater form a stable well flow". This is the basic standard to evaluate the sustainable exploitation of groundwater. In 2002, Bredehoeft, a famous American scholar, proved that the evaluation standard of "sustainable development" is exactly the same as the conclusion demonstrated by Professor Chen Chongxi in 1966. Over the years, the evaluation criteria of "groundwater recharge increment and discharge decrement" have been gradually respected and not criticized.
2. Groundwater dynamics analysis theory.
(1)1966 ~1981:Corrected the error of the model of "well flow affecting radius stability" and restored the original appearance of Qiu Buyi's "model around the island". Qiubuyi model is the most basic model for stabilizing well flow of groundwater. In 1950s, this model was introduced to China by the former Soviet Union as an "influence radius" model, and has been used as the main basis for groundwater resources evaluation for decades. Later, I learned that in Europe and America, the fur model was also described as the "influence radius" model. Until 1972, Xiong J, a famous scholar, said the same thing in his famous book Fluid Dynamics in Porous Media.
During the period of 1966, Professor Chen Chongxi questioned the model of "stable well flow with influence radius", and proved theoretically that the model could not form stable well flow not only under the original assumed initial head level, but also under the initial groundwater flow (runoff field with recharge). According to the principle of water balance, Mr. Chen Chongxi strictly proved the conditions for forming stable well flow.
1March 1974, Professor Chen Chongxi further pointed out that the application condition of Qiubuyi's stable well flow equation should be "island model" rather than "influence radius" model, and the "influence radius" in Qiubuyi's formula should be changed to "island radius". This theoretically corrected the mistake of "influence radius model" which was introduced from abroad in 1950s and had a far-reaching impact in China.
Professor Chen Chongxi's scientific opinions were quickly responded at that time. 65438-0975 invited Mr. Chen Chongxi to explain the understanding of Qiubuyi's stable well flow model to the Institute of Hydrogeology and Engineering Geology of Chinese Academy of Geological Sciences and colleagues in various provinces and cities in China, and systematically introduce the theory and method of unstable well flow of groundwater. Therefore, Professor Chen Chongxi wrote the earliest book in China that systematically expounded the theory of groundwater unstable well flow-Calculation Method of Groundwater Unstable Well Flow.
In the following years, Professor Chen Chongxi traveled all over the libraries and information offices in major cities in China, looking for the original fur, but failed. It was not until 198 1 that the client copied the original fur of Paris Library to 1863 that the true face of Lushan Mountain was clearly seen. The original work expresses the "roundabout model" proposed by Professor Chen Chongxi in 1974. Professor Chen Chongxi's persistent pursuit of this problem for more than ten years has not only corrected the long-term misinformation and misuse of hydrogeological literature, but also proved the theoretical error of the "stable radius well flow" model, and established the mass balance equation under the condition of groundwater exploitation on this basis, and determined the basic criteria for correctly evaluating the sustainable exploitation of groundwater.
(2) Broaden the application conditions of Theis formula and Hantushi formula. Both Tess model and Hantush model of overflow system assume the horizontal distribution of initial head, which is difficult to satisfy in nature. In 1975, Professor Chen proved that Theis formula and Hantush formula can broaden the flow field for initial stability; For the unstable initial flow field, it must be dynamically corrected by natural head before it can be used. Theis model requires the borehole diameter to be close to zero, and 1975 proves that Theis formula can only be used for the actual limited borehole diameter after pumping for a short time. In 2002 and 2003, in cooperation with graduate students, the revised Tess well flow model and Hantushi well flow model were put forward, and the analytical solutions were obtained, which proved theoretically that the depth of the gap between the two models was small at the initial stage of pumping.
(3) In 1966, the hydraulic model/equation of permeability coefficient of porous media and fractured media is established. This achievement reveals the physical essence of permeability coefficient, the most important parameter in hydrogeology. In 1972, Bear put forward the same hydraulic equation of permeability coefficient of porous media as Mr. Chen Chongxi, and in 1967, French scholar Louis also put forward a hydraulic model of fractured media similar to Mr. Chen.
(4) In 1974, the analytical solution of groundwater confined-unconfined unstable well flow considering the time-varying permeability coefficient of aquifer is proposed. Compared with Moench( 1972), the solution of freezing or melting around the conduit in heat conduction is directly transplanted to the problem of unstable well flow with and without pressure, and both have their own advantages and disadvantages. From 2006 to 2008, we cooperated with graduate students and made new achievements in this field.
(5) In the aspect of karst spring flow attenuation, the negative exponential function with attenuation coefficient α is commonly used to analyze and predict in the world, but this coefficient has always been used as an empirical parameter. In 1988, Professor Lin Min and Professor Chen Chongxi cooperated to obtain the hydraulic equations of attenuation coefficient in laminar flow and turbulent flow, revealing the relationship between attenuation coefficient and basic parameters of aquifer.
(6)20 1 1 established some basic analytical solutions of mixed well flow, and obtained some important understandings.
(7) Combining the advantages of unsteady flow analytical method and numerical method, the "numerical-analytical method" is put forward, which solves the difficulty of predicting groundwater exploitation performance by simple analytical method (1978 ~ 1980) and boundary treatment in numerical model (such as Hancheng water source, 65430) due to aquifer recharge.
3. Numerical simulation of groundwater flow.
(1) The aquifer system model in coastal areas is improved, and the theory and method for determining the maritime boundary are put forward. In many numerical models of coastal areas, domestic researchers regard coastline as vertical boundary; Most foreign countries are the same as above, and some researchers take a certain extension distance as the boundary, without any basis. From 1986 to 1988, Professor Chen Chongxi thinks that most water-bearing systems extend to the seabed, and summarizes different discharge types into the concept of "equivalent discharge boundary". At the same time, he proposed a method to determine the "equivalent discharge boundary" and hydrogeological parameters of coastal aquifers by using the tidal effect information of groundwater, which was used to evaluate the sustainable exploitation of groundwater in several water sources such as Beihai City, Yangpu Port Area of Hainan Island and Yantai City. This systematic and complete theory and method for determining the seabed boundary has important theoretical significance and practical value for establishing coastal hydrogeological model. (won the third prize of National Science and Technology Progress Award)
(2) The traditional borehole-water-bearing system model based on line confluence is upgraded to "seepage-pipe flow coupling model", which solves the hydrogeological problem of borehole boundary demarcation for a long time. In order to solve the simulation problem of mixed pumping wells, Professor Chen Chongxi proposed a "seepage-pipe flow coupling model". The model successfully solved the layered hydrogeological parameters determined by the two-layer mixed pumping test in Beihai (1992), the layered hydrogeological parameters determined by the three-layer mixed pumping test in Zhengzhou (1995) and the dynamic prediction of four groundwater mixed wells in northwest China (1999 ~ 2005). The new model and the application of mixed well examples have created a higher platform for the "borehole-water-bearing system model".
1995 further developed the "seepage-pipe flow coupling model" into the "karst pipeline-fracture-pore" groundwater "linear nonlinear flow model, which broke through the limitations of foreign dual-medium model and linear pipe flow model. The model has been successfully used to simulate the very complex spring dynamics in karst areas along the Yangtze River in Guangxi.
From 2003 to 2005, the "seepage-pipe flow coupling model" was applied to artesian wells and horizontal wells, which improved the original model to a higher level. In 2003, the traditional concept of observing the formation of well water level was questioned. Famous foreign scholars (Hantushi, бочевер, Newman, etc. It is considered that the head drop in conventional observation wells can be regarded as the average value of the drop at each point in the filter tube. However, Professor Chen Chongxi pointed out: "These methods for calculating the drawdown of observation well water level are pure mathematical methods lacking physical foundation", and the formation of observation well water level was simulated by "seepage-pipe flow coupling model". The solution of this problem has important theoretical significance and practical value.
In 2004, the physical simulation of "seepage-pipe flow coupling model" was completed to further verify the model. The results show that the head and flow dynamics of numerical simulation reproduce the results of physical simulation well. Therefore, it took Professor Chen Chongxi 10 years to put forward the theory of "seepage-pipe flow coupling model" and "equivalent permeability coefficient", to verify the physical simulation, and then to further test it in different conditions.
In 1992, Professor Chen put forward the "seepage-pipe flow coupling model", which overcame the unreality of the traditional model of drilling-water-bearing system based on line confluence, and moved the boundary of drilling from the filter pipe wall to the wellhead, without artificially giving the boundary conditions at the filter pipe wall, just giving the flow or head at the wellhead. This achievement raises the borehole-water-bearing system model used in hydrogeology for a long time to a new level. Professor Chen's fruitful work has made China a world leader in scientific research in related fields.
(3) The Ninth Five-Year National Science and Technology Project: Developing groundwater exploitation-land subsidence model (taking Suzhou area as an example). How to couple soil consolidation with groundwater flow? Professor Chen criticized the mistake of "two-step coupling" in the world and put forward the theoretical basis of one-step solution; Quasi-three-dimensional flow model has been widely used in the world. Professor Chen pointed out that the quasi-three-dimensional flow model is not suitable for multi-layer water-bearing system with "thousand-layer cake" weak permeable layer (the error is not less than 5%, but more than 30%), and the true three-dimensional model should be adopted; A water flow model considering the changes of porosity, permeability coefficient and water supply/storage coefficient caused by soil consolidation is established. This paper depicts the general law that land subsidence lags behind the head dynamics of groundwater exploitation layer, and objectively simulates the fact that the land subsidence center in Suzhou is inconsistent with the groundwater exploitation funnel.
(4) In 2003, it was put forward that "preventing simulation distortion and improving simulation are the core of numerical simulation". In numerical simulation, Professor Chen Chongxi emphasized the correct analysis of hydrogeological conditions, the study of water flow mechanism and the improvement of simulation technology, and completed more than 30 actual simulation models, which improved the numerical simulation technology of groundwater from both scientific and practical aspects. In 2005, I developed PGMS software with graduate students, which is better than MODFLOW on the whole. The software includes mixed pumping well, conventional observation well, artesian well, horizontal well, rainfall/channel, pumping well level, spring water flow, groundwater nonlinear evaporation, groundwater-surface water interaction and other modules.
4. Conclusion
Looking back on Professor Chen Chongxi's 50-year career, we can feel his sensitivity in finding scientific problems, his wisdom in solving problems, and his courage in correcting predecessors' mistakes and facing the truth. Professor Chen Chongxi has always praised academic contention, and believes that only by actively carrying out academic contention and communication can we better promote the development of the discipline. Mr. Chen Chongxi has always adhered to the academic thought of "seeking truth from facts" and persistently sought answers to scientific questions. He often teaches students "not only to learn how to solve problems, but also to cultivate the ability to discover and ask questions scientifically".
Mr. Chen Chongxi is cheerful and frank. His love for science, meticulous work style and spirit of overcoming difficulties as a scientist have deeply influenced his students and work partners.
(Excerpted from "An Overview of Professor Chen Chongxi's Academic Thoughts and Achievements" (Jiao et al., 2003, slightly supplemented).