In this paper, an integral geomechanical model test for Jintan arch dam is described. The dam is situated in complex rock formations. The failure mechanism, stability factors, and the interaction between arch dam and abutments are given.
Ce document decrit le test de modele geomecanique integral pour le barrage-voûte de Jintan. L'ampleur du modèle en question constitue l'une de plus importantes en Chine. Le barrage se trouve dans des formations de roche complexes. Il est egalement aborde dans le document le processus d'echec, les facteurs de stabitite et l'interaction entre le barrage-voûte et son fondement. Ils correspondent parfaitement aux calculs des resultats.
In der vorliegenden Arbeit wird ein integraler geomechanisch Modellversuch fuer Jinshuitan Bogenstaumauer vorgesstellt. Die Bogenstaumauer liegt auf der komplizierten felsformationen. Der Zerstoerungsmechanismus, die stabilitaetsfaktoren und die Interaktion zwischen der Bogenstaumauer und den seitlichen
In China, a number of large arch dams which are more than 100m in height have been constructed. In the design of arch dams, the stability problem of abutments is acquiring greater importance since the geological conditions in dam projects are becoming more and more complicated. Mathematical models and analytical methods have been extensively used in stability analysis. However, so far, they are inadequate in the case of geomechanical conditions concerning the stability of complex rock formations. For nearly 30 years, a permanent research laboratory at Tsinghua University specialising in physical model tests of arch dams has been established. Geomechanical models can be used for a great variety of purposes, mainly to demonstrate the deformation processes of the dams from normal load to rupture, and to examine the stability factors of abutments. They can provide a basis of information for the validity of the analytical results. The geomechanical model test for Jintan arch dam has been performed in our laboratory. It is a model test of the largest scale in China. Owing to the complex rock formations in Jintan arch dam project, the geomechanical model test has been utilized to check the results of numerical analysis. This paper will briefly examine this approach in analysing the stability of Jintan arch dam.
Jintan dam, a dome-shaped arch dam of 110m in height, is situated on the upper reach of Ou River in Zhejiang Province in the southeastern part of China. It is under construction at present. The geology for the dam site mainly consists of granite and gneissic granite as shown in Fig.l. The rock masses are slightly weathered and relatively intact. However, the abutment rock masses are cut into blocks by several large faults and three sets of main joints. As shown in Fig. 1, there were found some remarkable faults, such as F17, F11, F8, F12, F14 in the right abutment, F23,F31,F32 in the left abutment, and some gently dipped joints. Some infillings appear in these faults. Generally, these faults with their influenced zones are 0.1–0.3 meters wide. These discontinuities form the weak discontinuities in the rock abutments. The stability of abutments mainly involves in the behavior of these discontinuities. For the sake of assessment of Jintan arch dam stability and reliability, an integrated three dimensional model was utilized to investigate the dam behavior from under normal load to rupture. Considering the precision of observations and the size of testing table, the model scale was taken to be 1/100. The model has a length of 6m and a width of 5m.
In the model, different geological conditions including deformability, mechanical characteristics of the foundation rocks and the main discontinuities were reproduced, as given in Table (1). The average deformation modulus of intact rock in foundation and abutment of Jintan project is 2.2 × 104N/m2.
Under normal water load, the dam model behaved elastically and symmetrically. The maximum radial deflection, 5.4cm, was found at the crest of crown cantilever, whereas at the surface of foundation,0.558cm, as shown in Fig. 4.
Along the dam heel of the model, ten strain gages were stuck to the model surface to monitor the deformation of the model. In Fig.5, as λ=1.87, the upstream dam heel of the model behaved in a plastic state; as λ>3.2, some fissures emerged near the foundation of crown cantilever beam. When λ approached 3.47, the cracks spreaded over the left part of the heel and gradually to the right part. When λ =5.33, the upstream heel became entirely cracked. When λ=4.0, some fissures emerged in the downstream dam surface of the model, and near the foundation of the dam along the maximum principal stresses.
