土工格栅加筋掺砂黄土工程性质试验研究

为了寻找实用而有效的方法来降低用黄土填筑的桥头路堤沉降并提高其强度以避免桥头跳车，提出了在黄土中掺砂、用土工格栅加筋或两种方法同时采用的建议。为了研究这些建议的可行性，采用室内回弹模量试验和无侧限抗压试验分别研究了土工格栅加筋黄土和加筋掺砂黄土的变形和强度特性。对黄土和掺砂黄土分别完成了压实度为88%、92%和96%，加筋层数为0~5层组合工况下多组试样的回弹模量和无侧限抗压试验，对试验结果进行了详细的对比分析，得到以下结论：（1）掺砂和土工格栅加筋都可以明显提高黄土的回弹模量，两种方法同时使用效果更佳；（2）不管有无土工格栅加筋，掺砂都能使黄土强度大幅度提高，尤其在小应变下其提高的幅度更大；（3）在压实度不变而加筋层数增多时，或加筋层数不变而压实度下降时，土工格栅加筋掺砂黄土的应力-应变曲线由应变软化型逐渐向应变硬化型转变；（4）加筋掺砂黄土存在筋-土强度合理匹配问题，压实度高时应布置较密的加筋层，以使二者变形协调，从而实现加筋掺砂黄土强度的最大化。

Experimental study of engineering properties of geogrid-reinforced loess mixed with sand

In order to find out an effective and practical approach to reduce the settlement and increase the strength of an approach embankment filled with loess so as to avoid the bump at bridgehead, the methods were suggested by mixing a proportion of sand into the loess or reinforcing the loess with geogrid, or by using these two skills together. For examining essentially the feasibility of these ideas, the deformation and strength properties of geogrid-reinforced loess, loess mixed with sand (LMS) and geogrid-reinforced LMS were investigated in laboratory. A series of resilient modulus tests and unconfined compression tests were conducted respectively using samples made up of LMS or pure loess either with or without geogrid-inclusions. Each sample varied either in the number of reinforcement layers from 0 to 5, or in the degrees of compaction of 88%, 92% or 96%. Based on a detail analysis of the test results, the following conclusions are drawn: (1) The resilient modulus of the loess increases significantly either by mixed with sand or by reinforced with geogrid. More improvement is demonstrated while the both methods are applied together in a loess sample. (2) The compressive strength of LMS is much greater than that of loess when the LMS and the loess both are either with or without geogrid inclusions, especially under small compressive strain. (3) The compressive stress-strain pattern of a geogrid-reinforced LMS changes gradually from strain-softening to strain-hardening either while the geogrid layers increase at a certain degree of compaction or when the degree of compaction decreases at a given geogrid layers. (4) There is an appropriate strength match between the geogrid and the LMS, according to which a geogrid-reinforced LMS with higher density is suggested to be reinforced with smaller reinforcement spacing so as to obtain a maximum strength derived from a compatible deforming between the geogrid and the soil.