The prevision or estimation of rock durability is a very important and complex problem in engineering geology and civil engineering. Especially the durability of rocks for use as riprap of fill dams has a close relationship to their safety. The author has been studying on the durability of various rocks for use as riprap of fill dams by means of laboratory freezing and thawing test. As the first step, obtained results are as follows. (1) The deterioration characteristics of rocks are classified into following three types. A: No deterioration occurs in matrix itself. Sudden break to two or more pieces occurs along cracks after repeating certain freezing and thawing cycles. B: Progressive deterioration occurs in matrix itself. Exfoliation from the surface of test pieces occurs at any freezing and thawing cycles. C: Intermediate type between A and B. Type A rocks seem to be durable and no problem will occur for using as riprap of fill dams unless break will occur within the setting cycles. Durability of type B and C rocks can be estimated by the value of weight loss at the setting cycles. (2) Under freezing and thawing test, changes of saturation moisture content, effective porosity, dry density, coefficient of dynamic elasticity and shore hardness have a close relationship to the deterioration characteristics of rocks and can be classified into several patterns. (3) Freezing and thawing should be repeated at least 100 cycles to estimate rock durability. If it continues extra 100 cycles (i. e. 200 cycles), more precise estimation can be done on many deterioration characteristics of rocks, for example, the rate of deterioration. The rocks that weight loss occur less than 10% at 200 cycles are very durable and seem to cause no problem using for riprap of fill dams. (4) The durability of rocks can be estimated to some degree from initial value of the physico-mechanical properties. But such method is very rough and sometimes even unreliable. In order to estimate the durability of rocks more precisely, it is necessary to make direct accelerated deterioration experiments such as freezing and thawing test and measure various changes of physical properties.
We have tried the expression of Resistivity Cross Section which is adopted for the exploration of metalic are deposits for the survey of underground water. As the result of it, we believe that the method is available for the exploration of underground water which has complex behavior because the pattern of the apparent form and depth of the water bearing bed can be expressed on the section. Moreover, the model calculation by computer will raise the accuracy of analysis. Then we consider that the utilization of the Resistivity Cross Section will be increased to the civil engineering field.
Cracks and fissures contained in rock masses influence remarkably their own strength or drillability. Fissures have a primary influence on mechanical and elastic properties of rock. Such interrelation can be represented by the following empirical equation. n= 5.0/ (k+m) 2-4.0 Where, n: the frequency of fissures defined as the number of fissures per unit length (meter). k=υ/V (υ: the velocity of P-wave propagated in rock masses, V: the velocity of P-wave propagated in rock specimen) This ratio k gives the index to degree of fissuring. m: coefficient of uniformity, which depends on degree of weathering, porosity and strength. The strength of fissured rock masses Sf can be estimated as Sf=k2Ss if the strength of non-fissured rock specimen Ss and the index to degree of fissuring k are assumed.