大豆脲酶促沉碳酸钙改良砂土地基承载特性模型试验研究:基于静力触探试验

Study on the Improving Effect of Soybean Urease Induced Calcium Carbonate Precipitation on the Bearing Capacity of Sand Ground:Based on Results from Static Cone Penetration Tests

大豆脲酶促沉碳酸钙(SUICP)是一种新型土体改良技术,碳酸钙充填土内孔隙、胶结土颗粒,必将提高地基承载力。为了定量研究SUICP灌浆对砂土地基承载力的提高作用,开展了内径38.5 cm、高度100 cm的砂柱模型试验,碳酸钙沉积量为砂土质量的3%,基于静力触探试验对地基承载特性改良效果进行了研究。发现砂土地基SUICP灌浆处理前的锥尖阻力平均值为0.564 MPa,处理后平均值为0.783 MPa,增加38.9%;侧壁摩阻力处理前平均值为19.08 kPa,处理后平均值为26.92 kPa,增加49.83%;砂土地基承载力处理前平均值为79.02 kPa,处理后平均值为108.64 kPa,增加了45.09%。SUICP灌浆提高地基承载特性的原因包括两个方面,一是碳酸钙将砂土颗粒黏结在一起使得颗粒变大,二是碳酸钙的填充作用使得土体更加密实。通过本研究证实了SUICP灌浆对砂土地基承载力的提高作用,解释了发生机理。研究中也发现砂土地基改良的均匀性并不理想,还要进一步探索其发生机理,并研发更好的灌浆技术提高均匀性。

Soybean Urease Induced Calcium Carbonate Precipitation(SUICP) is a newly improveed technology of soil. The bearing capacity of ground is likely to be improved by filling effects and cementing function of precipitated calcium carbonate. In order to quantitatively investigate the improving effects of the SUICP on the bearing capacity of sand ground, we conducted a sand column model test, which was 38.5 cm in diameter and 100 cm in height. The calcium carbonate deposition was 3% of the mass of sand. The improving effects on the bearing capacity of sand ground was studied by static cone penetration tests. The results show that the average value of cone tip resistance of the sand ground increased by 38.9%, from 0.564 MPa to 0.783 MPa. The average shaft friction increased by 49.83%, from 19.08 kPa to 26.92 kPa. The average bearing capacity of sand ground increased by 45.09%, from 79.02 kPa to 108.64 kPa. There are two mechanisms for the improvement of bearing characteristics of sand ground.On one hand, sands of coarser particles were connected to each other by calcium carbonate. On the other hand, sands with denser pores were filled by precipitated calcium carbonate. The results confirm the SUICP grouting effects on the bearing capacity of sand ground and the mechanisms were analyzed. It is found that the uniformity of improvement in the sand column was not ideal,suggesting the need to explore the mechanism and to develop better technology in the future.