海洋钙质沉积物存在天然胶结作用,胶结程度对其力学性质具有重要影响。因天然钙质沉积物的胶结结构具有极大的不均匀性及胶结强度低等特点,使得获取原状试样难度大,加之距大陆遥远,取样成本高,从而限制了对其物理力学特性的研究进程。因此实验室快速制备胶结试样成为有效的解决办法,分别采用物理、化学及生物主导的试验方法开展胶结试样的制备研究,发现微生物诱导碳酸钙沉淀(microbially induced carbonate precipitation,简称MICP)和脲酶诱导碳酸钙沉淀(enzyme induced carbonate precipitation,简称EICP)可以促进碳酸钙晶体产生,从而生成类似天然胶结的人工胶结试样。通过扫描电子显微镜(scanning electron microscopy,简称SEM)、X射线计算机断层扫描(computed tomography scanned by X-ray,简称X-CT)和无侧限抗压试验,发现生物主导法得到的人工胶结物的矿物成分和晶体形貌均与天然胶结钙质沉积物相同,胶结试样峰值无侧限抗压强度能够达到天然弱胶结钙质沉积物的水平,通过X-CT分析建立了胶结时间-孔隙率-胶结度-力学特性之间的定量关系,从而将上千万年的天然胶结过程缩短到实验室可重现的时间尺度,该方法将对深入研究天然胶结钙质砂及礁灰岩等的形成机制具有重要的科学价值。然而,人工胶结试样目前还存在胶结度不均匀性、无法模拟白云岩化过程等不足。
Abstract
Natural cementation is a typical characteristic of marine calcareous sediments
such as calcareous rock and soil
and the degree of cementation has an important influence on its mechanical properties. Due to the great heterogeneity and low cement strength of cemented calcareous sediments
it is difficult and expensive to obtain natural cemented calcareous sediments from the oceangoing island
limiting research on their physical and mechanical properties. To effectively solve the above problems
this paper attempted using physical
and biological dominate method in the laboratory. It was found that microbially induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP) can promote the production of calcium carbonate crystals
generating artificially cemented specimens similar to the natural ones. The mineral composition
porosity and unconfined compressive strength of the biological artificially cemented specimens were analyzed by scanning electron microscopy (SEM)
computed tomography scanned by X-ray (X-CT) and unconfined compressive strength test. The mineral composition and crystal morphology of the artificial cementation were the same with the natural cemented calcareous sediments. The peak unconfined compressive strength of the artificially cemented sample could reach to the level of the natural weakly cemented calcareous sediments. The relationship between cemented time
porosity
degree of cementation and unconfined compressive strength was quantitatively determined. Therefore
the biological dominate method can shorten the natural cementation process from tens of millions of years to a period that can be reproduced in the laboratory
providing scientific value for exploring the formation mechanism of naturally cemented calcareous sand and reef limestone. However
it should be noted that there are some limitations in artificially cemented specimens
such as the degree of cementation is not fully uniform and dolomitized calcareous rock cannot be simulated.