土建筑遗址表面结皮形成与剥离机制研究

以交河故城土遗址为原型，通过现场调查、取样和室内试验，研究了土建筑表面结皮的物理化学性质，提出了土质墙体表面结皮的形成与剥离机制。粒度分析、粉晶X射线衍射分析、易溶盐离子色谱分析表明，与下伏母墙相比，结皮层粒度偏细，易溶盐含量偏低；红外摄像测温显示，结皮层升温、降温幅度更大。研究认为，土建筑遗址结皮层的形成是墙面土体局部饱和崩解、泥浆蠕移干燥的结果，其形成初期对抵抗土遗址风化起到一定的保护作用，但随后在剧烈的热胀冷缩作用及风蚀作用影响下发生剥离和脱落，反而加速土遗址的劣化进程。

Generation and detachment of surface crust on ancient earthen architectures

Field survey, systematic sampling and laboratory tests were conducted to study the weathering mechanism of earthen architecture taking the Jiaohe Relics site, Xinjiang, China for example. Particle size analysis, X-ray diffraction and chemical analysis of soluble salts illustrate that surface crusts are characterized by finer particles and lower soluble salts contents compared with the host soil. Temperature monitoring by IR thermography camera and thermal sensors shows that thin crusted layers response greatly and quickly to the environmental temperature change. It is concluded that the local saturation and slurry film generation due to rainfall are mainly responsible for the formation of surface crusts; and the crust will be subsequently detached by wind erosion and expansion-contraction induced by the change of temperature. Surface crusted layer prevents the wall from weathering to some degree at its earlier formation stage but tend to accelerate the deterioration of the earthen architectures in the long term considering that Jiaohe site suffer from strong sandstorm and strict weather condition.