Deep mixing (DM) techniques using cement and lime mixtures have been used to stabilize weak soils, install excavation support, mitigate liquefaction problems and stabilize steep embankments and slopes. Rigorous quality assurance techniques are needed to assess field construction operations since deep mixed soil cement columns in the field are influenced by mixing methods, soil types, constrcution techniques, and mix design methods used in the projects. Current methods of verification of treated soil improvements using field coring and laboratory testing suffer from sampling problems such as rigidity of the sampler, locking of the sampler and rotation of the sampling core with the sampler. Hence, in situ based techniques are often used for strength based quality assessment (QA) studies. As a part of the research study conducted for the National Deep Mixing program, various case studies involving the use of in situ methods for QA studies of treated soil columns across the World are compiled. This data was used to develop different in situ methods based protocols to perform QA investigations. This paper presents two frequently used in situ methods, standard penetration test (SPT) and cone penetration test (CPT) for strength assessments. Several case study results are used to evaluate the use of these test protocols for assessing strength improvements of cement and lime treated soil columns.