Contact metamorphism and metasomatism are imposed on granitic rocks by late intrusions. This study shows the consequences of this phenomenon on the pedogenesis of granitic rocks and on the geotechnical properties of granitic residual soils. This study comprises two saprolitic soils formed from the same granitic body in a site located in the Southern Brazil Coast. A biotite-rich residual soil (BR soil) was formed in the vicinity of a dyke that crosses the study area and concentrates a history of landslides. The second soil, a red saprolitic residual soil (RR soil), was formed far from the intruded fault. Chemical, physical, and mineralogical characterizations were carried out to describe the materials and the changes imposed by their alteration. Effects of alteration on the soil’s behavior were assessed in terms of hydraulic conductivity, one-dimensional compressibility, and shear strength. Both soils presented a fragmented structure and cataclastic texture over feldspar matrices. The good drainage conditions induced the development of large amounts of kaolinite. Suction values increase with the alteration level and hydraulic conductivity decreases. Under oedometric loading BR soil is stiffer than RR soil, despite its higher porosity. RR soil has higher shear strength than BR soil, which explains the history of landslides that mobilize this soil.

晚期侵入作用对花岗岩施加接触变质作用和交代作用。本研究显示了这种现象对花岗岩成土作用和花岗岩残余土的岩土特性的影响。这项研究包括在位于巴西南部海岸的一个地点由同一花岗岩体形成的两种腐泥土。在穿过研究区的堤坝附近形成了富含黑云母的残余土壤（BR 土壤），并集中了滑坡的历史。第二种土壤是红色腐泥土（RR 土壤），形成于远离侵入断层的地方。进行了化学、物理和矿物学表征以描述材料及其改变所带来的变化。根据水力传导率评估改变对土壤行为的影响，一维压缩性和剪切强度。两种土壤在长石基质上都呈现出破碎的结构和碎裂质地。良好的排水条件促进了大量高岭石的发育。吸力值随着变化水平和水力传导率的降低而增加。在定力载荷下，BR 土比 RR 土更硬，尽管其孔隙率更高。RR 土壤比 BR 土壤具有更高的剪切强度，这解释了移动这种土壤的滑坡的历史。在定力载荷下，BR 土比 RR 土更硬，尽管其孔隙率更高。RR 土壤比 BR 土壤具有更高的剪切强度，这解释了移动这种土壤的滑坡的历史。在定力载荷下，BR 土比 RR 土更硬，尽管其孔隙率更高。RR 土壤比 BR 土壤具有更高的剪切强度，这解释了移动这种土壤的滑坡的历史。