Abstract:Preservation of historical earthen ruins against damage is one of the difficult problems. The main geological issues of such earthen ruins are weathering,cracking and falling of the surface soil. Conventionally used soil nailing and chemical grouting techniques have the following limitations when applied to strengthen these ruins. One is that the large diameter of drill hole will disturb the soil ruins and leave evident spots of appearance. The second one is that chemical grouts flow towards ground surface and will also spoil the appearance of the soil ruins. And also the high injection pressure may lead to micro-cracks inside the earthen ruins. Further spraying chemical grouts on the surface is frequently used in practice,but the permeation quantity and solidification effect are difficult to evaluate. From the objectives of strengthening and preserving Dougaeri historical earthen kiln No.2,the micro-soil nailing and mini-chemical grouting techniques have been developed to overcome the above limitations. The two techniques can be used together or individually according to the specific requirements. The important micro-equipments developed are mortar injector and balloon cover injection tip,which are suitable for nailing and chemical grouting in micro drill holes(f 5–7 mm). The feasibility and adaptability of the techniques have been evaluated in a field model kiln test. A fast Lagrangian analysis of continua(FLAC) code has been employed to perform stability analysis. The reinforcement design with the micro-techniques has been presented considering the different stabilities and possible failure modes at different locations of the kiln. The recommended design has been successfully applied to the practical works. It is envisaged that the micro techniques will have broad applications to strengthening and preserving historical earthen ruins due to its portability,little disturbance and well-field adaptability.