- 期刊
超細水泥漿液滲透灌漿之研究
The Study of Permeation Grouting with Microfine Cement Grout
摘要
基礎施工階段，經常會遭遇透水性很高或者不穩定之鬆散土壤，必須進行滲透灌漿改良地盤，但是由於灌漿材料及黏滯度選擇不當或者灌漿壓力不當，造成無法達成地盤改良之要求，導致基礎開挖失敗（砂湧、管湧及隆起等現象）或無法達到鄰房保護目的之案例時有所聞。 有鑑於此，本研究建立一套系統來決定滲透灌漿的漿材種類、漿液配比、灌漿壓力及灌漿流量，提高滲透灌漿的施工品質。本研究利用超細水泥為漿材，透過這一套系統來驗證其可行性。首先進行超細水泥的基本性質試驗，包括比重試驗、凝結時間試驗及泌水試驗。利用Brookfield RVDV-Ⅱ(上標 +)黏滯度儀，測試不同配比與不同剪應變速率下漿液的流變行為。再利用本研究建製的可灌度設備，製作直徑3.78公分，高度36.8公分的試體，快速篩選已知地盤所適合的漿材、漿液配比與灌漿壓力，並在可灌度試驗後利用濕式養護試體7天，再進行試體改良後的透水試驗與抗壓試驗，評估試體改良後的力學特性。另外，利用地盤灌漿模型設備，以濕式霣降方式製作直徑93公分，高度142公分的不良級配砂土試體，經模擬地下砂土的應力狀況後，使用水灰比為3，分散劑為2%的超細水泥漿液進行低壓灌漿，經由監測儀器記錄灌漿壓力與灌漿流量之歷時關係，並且在灌漿試驗後開挖試體，探討灌漿壓力、灌漿流量、灌漿範圍及灌漿機制。研究結果顯示，超細水泥漿液的凝結時間與泌水量會隨著不同的水灰比、分散劑添加量及靜置時間而有所變化。在流變性質上，超細水泥漿液屬於賓漢流體。在可灌度試驗中，漿液在砂土試體的滲透能力是隨著漿液水灰比與灌漿壓力的增加而增加；但是對於改良後砂土試體而言，在相同灌漿壓力下，水灰比較大的漿液，其滲透能力比水灰比小的漿液好，但是由於漿液水灰比大，漿液與砂土的膠結能力較差，故改良後砂土試體的滲透係數較大，並且抗壓強度較弱。至於地盤灌漿模型試驗的結果可得知，超細水泥漿液注入約勻係數C(下標 u)為3.71與曲率係數C(下標 d)為0.86的不良級配砂土中，累積灌漿流量為2,650ml，改良土壤體積為6,875ml，由土壤孔隙率評估漿液的體積約3,066ml，其灌注型態屬於滲透灌漿。
並列摘要
During underground construction, the loose soil deposit with high permeability or low stability is often encountered, and the permeation grouting is needed to improve the ground condition. However, due to selecting unsuitable grout material, grout viscosity and injection pressure, the purpose of ground improvement cannot be achieved. This may cause excavation failure and endanger the adjacent buildings due to sand boiling, piping and uplifting problems. This study establishes a system to evaluate the suitable grout type, grout viscosity, injection pressure and injection rate of permeation grouting. A microfine cement is used to run through this system for a testing. First, specific gravity, setting time and stability testing of microfine cement are tested. Then viscometer is used to evaluate the rheology of microfine cement grout under various shear speeds. The penetrability testing on cylindrical sample (3.78cm in diameter and 36.8cm in height) is conducted to verify the penetrability of grout, which can be evaluated by Penetrability Ratio on the base of the gradations of soil and grout. The grouted soil samples are tested for coefficient of permeability and unconfined compression strength. Finally, the same soil deposit is prepared in the calibration chamber for permeation grouting. The grout is made of microfine cement with water-to-cement ratio of 3 plus 2% dispersant by weight of cement. The injection pressure and grout take are monitored during grouting. The grouted soil is excavated to study the size and shape of treated zone, and the permeation grouting mechanism. The testing results indicate that the setting time and bleeding will vary with water-to-cement ratio, dispersant content and curing time. The behavior of microfine cement grout is similar to Bingham fluid. The penetrability of grout improves when water-to-cement ratio and injection pressure increase. However, in the grouted soil, the coefficient of permeability increases and unconfined compression strength decreases when water-to-cement ratio increases. The permeation grouting in a poorly graded sand with C(subscript u) at 3.71 and C(subscript d) at 0.86 is successful, the monitored grout take is 2650ml and is closed to estimated grout take 3066ml from the volume of grouted soil.