In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

Abstract

Highly sensitive, low-saline clays, termed quick clays, represent a risk for large landslides. An in-situ experiment was conducted installing salt wells filled with potassium chloride (KCl) in order to study how salt wells can be used to reduce landslide risk. The salt-plume migration and the clay volume surrounding the salt wells were investigated by resistivity cone penetration tests (RCPTU), piston samples, conductivity divers and groundwater samples. Correlating the geotechnical properties to the occurring pore-water compositions, the remolded shear strength (cur) was improved beyond 1 kPa when the ratio of the sum of potassium, magnesium and calcium over the major cations exceeded 20%. The cur was improved to about 4-8 kPa 0.5 m from the wells within 3 years, and the liquidity index decreased from more than 3.4 to less than 1.2. A diameter of minimum 1.5 m around the wells was stabilized within 3 years. Thus, it is recommended to install the salt wells with a center-to-center distance of 1.5-2.0 m. The improved post-failure properties (cur and Atterberg limits) are considered permanent in an engineering time scale due to a lasting pore-water composition inhibiting development of high sensitivity. Salt wells can be installed without substantial disturbance of the soil, and can be used as landslide mitigation in quick-clay areas.

Characterization of a gold tailings with hypersaline pore fluid

“…Kay et al 2005) and around salt wells used for remediation of sensitive clays (e.g. Helle et al 2017). Hypersaline conditions mean that the potential effects of salt extend beyond changes to fabric and clay mineralogy.…”

“…Therefore, it is conceivable that some of the differences seen by Chang et al between slurry prepared specimens (with flocculant) and other reconstitution techniques (that did not involve use of a flocculant) may be a result of the presence of the flocculants themselves, which are known to affect the CSL (Reid and Fourie 2016). Mitchell and Soga (2005) and Helle et al (2017) summarise and further discuss the development of sensitivity in clays, particularly the observation that reduction in salt concentration is generally insufficient, in itself, to generate highly sensitive soils.…”

“…A resulting ratio of greater than 0.75 is required for very high sensitives to develop. Alternatively, Helle et al (2017) emphasise the greater importance of K+ to Na+, and propose an alternative ratio to assess potentially high sensitivity (defined as remoulded shear strength < 1 kPa), as follows: K + + Mg 2 + + Ca 2 + Na + + K + + Ca 2 + + Mg 2 +…”

Molecular dynamics simulation of water molecules adsorption by different cations based montmorillonite

“…王进等人 [18] 运用分子动力学方法, 利用Materials Stu- [21,22] , 非常有必要进一 步研究Ca 2+ 蒙脱石的吸水膨胀特性. 含有K + 的化学试 剂也被用于改良膨胀土 [23,24] , 其机理仍然不很清楚, [25] . UFF力场几乎包含 了所有的元素, 适应范围很广, 文献中也采用了这一 力场 [11,18~20] , 因此本文也选择了UFF力场.…”

Effectiveness of resistivity cone penetration tests in salt-treated highly sensitive clay

“…Electrical resistivity tomography (ERT) allows a relatively quick and cheap mapping of large areas, and low-saline Norwegian quick clays may be indicated at electrical resistivity values in the range 10-100 Ωm (Solberg et al, 2012;Long et al, 2012), corresponding to conductivity values of 100-10 mS/m. Low-saline, clays with electrical resistivity values within the "quick range" do not necessarily imply quick clays, as the development of high sensitivity in leached low-saline, illitic-chloritic clays is governed by the composition of cations in the pore water (van Olphen, 1963;Penner, 1965;Moum et al, 1971;Rosenqvist, 1968;Torrance, 1983;Helle et al, 2016;Helle et al, 2017). Clays with low-saline pore-water compositions dominated by sodium (Na + ) may develop high sensitivity (Penner, 1965;Torrance, 1983;Mitchell and Soga, 2005), whereas low-saline clays with a ratio of the sum of the equivalents of potassium (K + ), magnesium (Mg 2+ ) and calcium (Ca 2+ ) over the sum of Na + , K + , Mg 2+ and Ca 2+ (major cations) exceeding 20% do not (Helle et al, 2017).…”