From 65438 to 0948, when he was studying at Delft University of Science and Technology, he analyzed the causes of pile foundation failure two years after the completion of Wlaggemans Bridge in the Netherlands. At that time, the engineering community generally believed that this was caused by pore pressure. However, Chen Zongji thinks that the pore pressure in soil will gradually disappear with time, while the deformation under shear stress will increase with time, so he puts forward a new concept that rheological characteristics, triaxial stress and large deformation of soil must be considered in soil mechanics theory. In order to develop this new concept, Delft University of Science and Technology in the Netherlands specially allocated funds for his research. Later, Delft Institute of Soil Mechanics hired him to further carry out related research work. 1952- 1954, under the guidance of Professor Borges, a famous physicist and mechanic of the Royal Dutch Academy of Sciences, he introduced the principles of modern rheology, plastic mechanics and colloid chemistry, systematically carried out experimental research and theoretical exploration of soil rheology, established soil rheology at the earliest in the world, and opened up a new research way for soil mechanics. 65438-0954 was awarded a certificate by Delft University of Science and Technology for his outstanding achievements in studying soil rheology in the Netherlands. After 1955 returned to China, a large number of experimental studies were carried out on loess and coastal soft soil in China, which further developed and enriched soil rheology, put forward the basic principle of micro-rheology of loess structure and its special mechanical properties in China, and developed new experimental instruments. 1978 won the research award of soil rheology in the first national science conference.
Chen Zongji expounded the rheological and failure characteristics of clay through experimental study, and put forward a new theory of "Clay Structural Mechanics" for the first time in the world (1954, 1957). 1959 his theory was confirmed by the observation of Norwegian physical chemist Rosenwest with electron microscope. This theory of Chen Zongji has been compiled into foreign textbooks. Chen Zongji first put forward the theory of three-dimensional consolidation rheology of soil in the world (1953- 1956). Prior to this, it was generally believed that the time factor was caused by consolidation. Chen Zongji's theory emphasizes that the creep of soil skeleton caused by deviatoric stress tensor plays an important role, while the time effect caused by spherical stress tensor is very limited. Through experiments and theoretical deduction, he obtained the long-standing unsolved problem of sub-time effect in soil mechanics. From 65438 to 0956, he solved the problems of one-way and two-way finishing and sub-time effect with his own three-way finishing theory. 196 1 year, he developed this theory into a linear anisotropic discipline. 1964, developed into a nonlinear rheological consolidation problem.
Chen Zongji discovered for the first time in the world that clay has three deformation stages and three yield values (f 1, f2, f3), and the concept of the third yield value f3 or the highest yield value is of great significance to the long-term stability of the project. In 196 1, Chen Zongji suggested that the third yield value f3 should be used for stability calculation in engineering design. This view has been highly valued at the General Assembly of the International Society of Soil Mechanics and Basic Engineering and the General Assembly of Rheology and Soil Mechanics of the International theoretical and applied mechanics Society. This yield value is called "Chen yield value". Chen Zongji also explored the rheological characteristics of soil under dynamic load, and in 1958, he developed two kinds of soil dynamic triaxial apparatus for the first time in the world. Chen Zongji's research methods and achievements in soil rheology are also applicable to weak structural planes in soft rock mass and hard rock mass. Chen Zongji has written more than 70 papers on soil rheology. These papers are widely circulated in the Netherlands, France, Sweden, Portugal, the former Soviet Union, Japan, Poland, the former Yugoslavia and the United States, and have attracted great attention from the international soil mechanics community.
In the aspect of rock rheology, Chen Zongji took the lead in carrying out rheological tests in the surrounding rock of the tunnel of the Three Gorges Project on the Yangtze River in 1959. At that time, only a few people in the world noticed this problem. In 196 1, he extended the rheological theory of rock mass to anisotropic rock mass. 1965, according to the experimental study of jointed rock strata, he solved the problem of stress distribution of tunnel surrounding rock in layered rock mass theoretically, put forward two concepts: surrounding rock stress rotates with time and lining stress increases with time due to rheological rebound of rock mass, and pointed out the irrationality of Platts theory widely used at that time. In 1970s, based on the study of rock microstructure and considering the origin and history of rock mass, he put forward the theory of the source and release of internal stress in rock mass, and pointed out that there must be dislocations, cracks and in-situ stresses in natural rock mass, which led to the rheological characteristics of rock mass. According to the experimental observation and theoretical analysis, he also put forward the constitutive equation of rock dilatancy. 1979 published the paper "rock sealing stress, creep, dilatancy and constitutive equation". 198 1 year, based on the study of argillaceous interlayer in the foundation of Gezhouba water control project on the Yangtze River, the paper "Shear stress relaxation and creep characteristics of argillaceous interlayer and its importance in dam engineering design" was written and published at the international soft rock academic conference (Tokyo, Japan). 1983, he further developed the theory of rheological dilatancy, and published a paper entitled "Rock Failure and Time-related Dilatation before Earthquake" at the Fifth International Conference on Rock Mechanics (Melbourne, Australia), and studied the deformation mechanism of expansive rocks from the perspective of rheology. From 65438 to 0984, he gave an academic report entitled "The Third Yield Value of Rock and Soil and Its Importance in Engineering" at the Royal College of Science, Literature and Art in Belgium, which was highly praised. In the same year, he was hired as an academician of the Royal Belgian Academy of Science, Literature and Arts. 1986 was awarded the title of "Knight of Leopold II" by the Belgian King, and was awarded a medal and a certificate of honor. From 65438 to 0988, based on the principle of rheology, Chen Zongji creatively studied the construction of NATM tunnel around the topics of creep, expansion and tectonic stress of surrounding rock. According to his constitutive equation, the stability of surrounding rock is analyzed by finite element method. On this basis, reasonable suggestions are put forward for the reinforcement measures of tunnel surrounding rock. 1989, Chen Zongji published a paper "Measuring the Expansion, Creep and Relaxation of Brittle Rock with 8000kN Multifunctional Triaxial Instrument". In this paper, a new type of 8000kN servo-controlled multifunctional triaxial apparatus is introduced comprehensively, and a new method to determine the dilatancy parameters of rocks in the brittle range is systematically introduced, and the dilatancy process related to time is analyzed. In the test, the highest confining pressure is 400MPa and the highest temperature is 250℃.