在三维空间中，常规应变状态由3个正应变和3个剪应变来描述。因此，确定一点的应变状态至少需要6个应变测试元件。基于应变状态理论，设计了一种能测试混凝土、岩土等材料内部应变状态的接触式三维应变花。该测试装置的核心由6个常规应变片组成，且应变片的布置需要满足特定条件。根据任一方向上线应变与常规应变表示方法中三维应变各分量之间的关系，建立了三维应变花各测试数据与常规应变之间的转换矩阵。进一步给出了求解该问题的必要条件，并进行了误差分析。考虑施工便利性要求，着重阐明了直角式三维应变花和正四面体式三维应变花的应变片布置方式，并给出了对应的计算方法。两种三维应变花的自身测试和对某试样应变状态的测试表明，该方法可对混凝土、岩土等材料内部的三维应变状态进行测试。

In the three-dimensional space, the conventional strain state is expressed by three normal strains and three shear strains. Therefore, six strain gauges at least are required to determine the strain state of a point. Based on the strain state theory, a contacting three-dimensional strain rosette that can measure strain in concrete or geomaterials is developed. The device is made up of six strain gauges, and the layout of strain gauges must meet a special condition. According to the relations of components of strain between representations for the conventional strain and the linear strain in an arbitrary direction, transition matrix is built to bridge relationships between the test results and the traditional strain state. Subsequently, the solution qualification is derived and expatiated in order to illustrate the layout of the six strain gauges. The two schemes, namely the orthogonal tetrahedron and the normal tetrahedron, are studied in detail after considering the construction convenience, rational and logical methods are constructed. The tests on the device itself and further on a rectangular shaped sample made of mortar show that the two three-dimensional strain rosette is reasonable and convenient to measure the strain state of concrete, rock and soil in engineering.